DEV Community: Christian Ahrweiler

Quantencomputing verständlich erklärt — Episode 1

Christian Ahrweiler — Wed, 23 Sep 2026 09:53:16 +0000

Quantencomputing verständlich erklärt### Vom Bit zum Qubit

Quantencomputer werden häufig mit einem Satz erklärt, der beeindruckend klingt:

*Ein gewöhnliches Bit ist entweder 0 oder 1. Ein Qubit kann dagegen 0 und 1 gleichzeitig sein.*Das klingt, als könne ein Qubit zwei klassische Werte gleichzeitig speichern. Ein Quantencomputer müsste dann nur genügend Qubits besitzen, um alle denkbaren Werte parallel zu verarbeiten.

So funktioniert es nicht.

Um den Unterschied wirklich zu verstehen, beginnen wir nicht mit Quantenphysik, sondern mit dem bekannten Computer: mit Bits, Schaltzuständen und Programmen.

Ein Bit besitzt einen Schaltzustand

Ein Bit kann einen von zwei Werten besitzen:

SchaltzustandWertAus0Ein1

„Aus“ und „Ein“ sind nur eine vereinfachte Vorstellung. In einem realen Computer können beispielsweise zwei unterschiedliche Spannungsbereiche für 0 und 1 stehen.

Entscheidend ist: Ein klassisches Bit befindet sich zu einem bestimmten Zeitpunkt in einem der beiden Schaltzustände. Beim Auslesen erhalten wir deshalb entweder 0 oder 1.

Ein Programm verändert Schaltzustände

Bevor ein Prozessor rechnen kann, werden Bits auf Ausgangswerte gesetzt. Danach führt der Prozessor die Befehle eines Programms aus. Elektrische Signale verändern dabei die Schaltzustände der Bits. Am Ende wird das Ergebnis ausgelesen.

Vereinfacht sieht der Ablauf so aus:

Bits auf Ausgangswerte setzen
↓
Programm ausführen
↓
Schaltzustände verändern sich
↓
Ergebnis auslesenEin einzelner Maschinenbefehl kann beispielsweise den Wert eines Bits umkehren:

Ausgangswert: 0
↓
Befehl: Wert umkehren
↓
Ergebnis: 1Wenn wir den Ausgangswert und den ausgeführten Befehl kennen, können wir den neuen Wert eindeutig bestimmen.

Ein Qubit ist ebenfalls ein physisches Bauteil

Auch ein Qubit ist kein rein mathematisches Zeichen, sondern wird durch ein physisches System dargestellt.

Qubits können unterschiedlich gebaut werden. Manche Quantencomputer verwenden einzelne Atome oder Ionen, andere verwenden Lichtteilchen. Bei supraleitenden Quantencomputern dient ein winziger elektrischer Schaltkreis als Qubit.

Ein solches Qubit besitzt zwei Zustände, die bei einer Messung unterschieden werden können. Diese Messergebnisse nennen wir ebenfalls 0 und 1.

Bis hierhin ähnelt ein Qubit einem klassischen Bit:

Klassischer ComputerQuantencomputerBitQubitSchaltzustände 0 und 1Messergebnisse 0 und 1MaschinenbefehlQuantengatterelektrische SchaltsignaleSteuersignale für QubitsProgrammFolge von QuantengatternErgebnis auslesenQubits messen

Ein Quantengatter entspricht ungefähr einem Maschinenbefehl

Ein Quantenprogramm besteht aus einer Folge von Quantengattern. Ein Quantengatter entspricht ungefähr einem Maschinenbefehl eines gewöhnlichen Computers.

Das Quantengatter ist zunächst eine Anweisung wie:

Wende Gatter H auf Qubit 1 anDie Steuerelektronik des Quantencomputers übersetzt diese Anweisung in ein genau geformtes physisches Signal. Bei einem supraleitenden Qubit ist das beispielsweise ein Mikrowellensignal. Das Signal wirkt für eine bestimmte Zeit auf den Qubit und verändert seinen Zustand.

Ein Quantenprogramm läuft damit vereinfacht so ab:

Qubits auf Ausgangswerte setzen
↓
Quantengatter ausführen
↓
Steuersignale verändern die Qubits
↓
Qubits messen### Warum wird am Ende gemessen?

Der Qubit wird nicht auf einen fertigen Ergebniswert gesetzt und anschließend wieder ausgelesen. Vor der Berechnung wird lediglich ein bekannter Ausgangswert hergestellt, beispielsweise 0.

Danach verändert das Quantenprogramm den Qubit. Die abschließende Messung liefert das Ergebnis der Berechnung als gewöhnlichen Wert 0 oder 1.

Der Ablauf entspricht damit dem bekannten Prinzip:

Eingabe festlegen
↓
Programm ausführen
↓
Ausgabe lesenBeim Quantencomputer lautet derselbe Ablauf:

Qubit auf 0 setzen
↓
Quantengatter ausführen
↓
Qubit messen### Der entscheidende Unterschied

Ein klassischer Befehl überführt bekannte Bitwerte in neue, eindeutig bestimmbare Bitwerte.

Ein Quantengatter kann ebenfalls ein eindeutiges Ergebnis erzeugen. Ein bestimmtes Gatter kann beispielsweise aus 0 sicher 1 machen.

Ausgang: 0
↓
Quantengatter
↓
Messung: 1Ein anderes Quantengatter kann den Qubit jedoch so verändern, dass die anschließende Messung nicht immer dasselbe Ergebnis liefert.

Um das zu beobachten, führen wir nicht nur die Messung, sondern den vollständigen Ablauf mehrmals aus:

Qubit auf 0 setzen → dasselbe Quantengatter → messen: 0
Qubit auf 0 setzen → dasselbe Quantengatter → messen: 1
Qubit auf 0 setzen → dasselbe Quantengatter → messen: 1
Qubit auf 0 setzen → dasselbe Quantengatter → messen: 0Vor jeder Ausführung wird der Qubit wieder auf 0 gesetzt. Danach wird jedes Mal dasselbe Quantengatter angewendet. Trotzdem kann die Messung 0 oder 1 liefern.

Das Quantengatter hat den Qubit also nicht einfach auf einen unbekannten klassischen Schaltzustand gesetzt. Es hat einen Quantenzustand erzeugt.

Was bedeutet Wahrscheinlichkeit bei einer Messung?

Nehmen wir an, wir führen den vollständigen Ablauf 100-mal aus:

auf 0 setzen → Quantengatter anwenden → messenJede Ausführung liefert genau ein Messergebnis. Angenommen, wir zählen:

50 Messungen mit dem Ergebnis 0
50 Messungen mit dem Ergebnis 1Dann erhalten wir bei diesem Ablauf ungefähr:

50 % Wahrscheinlichkeit für 0
50 % Wahrscheinlichkeit für 1Die 50 Prozent sagen nicht voraus, welches Ergebnis die nächste einzelne Messung liefern wird. Sie beschreiben, wie sich die Ergebnisse bei vielen Wiederholungen verteilen.

Bei zehn Ausführungen könnten wir sechsmal 0 und viermal 1 messen. Nach vielen Tausend Ausführungen lässt sich wesentlich genauer erkennen, welcher Anteil der Messungen 0 und welcher Anteil 1 ergibt.

Damit kennen wir den äußeren Ablauf eines Quantenprogramms: Ein bekannter Eingangszustand wird vorbereitet, Quantengatter verändern das Qubit und eine abschließende Messung liefert 0 oder 1.

Mit einem Missverständnis aufräumen

Missverständnis:* Ein Qubit kann gleichzeitig 0 und 1 sein und deshalb zwei klassische Werte auf einmal speichern.*Tatsächlich liefert eine einzelne Messung immer nur 0 oder 1. Das Quantengatter hat vorher einen Quantenzustand erzeugt — nicht zwei gleichzeitig auslesbare klassische Werte.Noch ungeklärt ist, welchen Zustand ein Gatter erzeugt, wenn die anschließende Messung nicht immer dasselbe Ergebnis liefert. In Episode 2 beschreiben wir diesen Zustand mit zwei Koordinaten — den Amplituden — und verfolgen erstmals konkret, wie ein Quantengatter damit rechnet.

Blockchain and Bitcoin Explained in 6 Episodes — Bonus Episode

Christian Ahrweiler — Tue, 22 Sep 2026 17:20:03 +0000

Why Is Bitcoin Called a Cryptocurrency?Why Is Bitcoin Called a Cryptocurrency?Cryptography is usually associated with encryption. Data is transformed so that it can only be read again with the appropriate key.

Bitcoin, however, is not encrypted.

The Bitcoin blockchain is public. Anyone can read its blocks and transactions. The amounts transferred are generally visible as well.

Bitcoin Is Public but Pseudonymous

The Bitcoin blockchain makes it possible to trace which amounts a Bitcoin address has received and later spent.

However, the address does not contain a name. At first, the blockchain only shows the flow of payments between different addresses.

Publicly visible:
Bitcoin addresses
Amounts
Transactions
Timestamps

Not directly visible:
Names
People
Purpose of the paymentIf an address is linked to a person or company, its previous transactions can also be traced.

Bitcoin is therefore not anonymous but pseudonymous.

Although this data is public, Bitcoin uses several cryptographic methods. However, they are not used to encrypt transactions.

Why, then, is Bitcoin called a cryptocurrency?

Because cryptography is not only used to keep information secret. It can also make data verifiable, assign control, and confirm digital authorizations.

Bitcoin uses cryptographic methods in three essential places:

Cryptographic hash functions
Make data and computational work verifiable

Cryptographic key pairs
Control who can spend Bitcoin

Digital signatures
Provide verifiable authorization for transactionsLet us take a closer look at these three methods.

1. Cryptographic Hash Functions

In Episode 1, we calculated simplified hashes from short texts:

Text Hello Anna!
Hash 3dcdffText Hello Anne!
Hash 2dededThese short hashes were only used to make the principle easier to understand.

Bitcoin uses a real cryptographic hash function called SHA-256.

SHA stands for Secure Hash Algorithm. The number 256 describes the length of the result.

Internally, a SHA-256 hash always consists of 256 bits.

A bit can have one of two values:

0 or 1Written this way, a SHA-256 hash would be a sequence of 256 zeros and ones:

101101001011011010101100…This representation would be very long and difficult for people to read. Therefore, every four bits are combined into one character.

Four bits have 16 possible combinations:

0000
0001
0010
0011
…
1111The following characters are used to represent these 16 possibilities:

0 1 2 3 4 5 6 7 8 9 a b c d e fThis is called hexadecimal notation.

One character therefore replaces four bits:

4 bits = 1 characterIt follows that:

256 bits ÷ 4
↓
64 charactersA complete SHA-256 hash is therefore normally displayed using 64 characters.

A real hash might look like this:

00000000000000000001a7f4c8b2…The dots are not part of the hash. They only indicate that we have shortened the value for this example.### What Makes SHA-256 Cryptographic?

SHA-256 has several important properties:

The same content always produces the same hash.
Even a small change produces a completely different hash.
The original content cannot be calculated from the hash. A hash function is therefore a one-way function.

Can Two Different Contents Have the Same Hash?

SHA-256 can map content of any size to a hash containing only 256 bits.

Because there are more possible contents than possible hashes, different contents producing the same hash must theoretically exist.

This is called a collision.

However, SHA-256 has such an unimaginably large number of possible hashes that an accidental collision is not expected in practice.

For verification purposes, we can therefore say:

Hashes are different:
The contents are different

Hashes are identical:
The contents are identical with extremely high probability### How Does Bitcoin Use SHA-256?

Bitcoin uses SHA-256 for purposes including its block hashes and Proof of Work.

Block data

previous hash
nonce ↓ SHA-256 ↓ Block hashDuring mining, the nonce is repeatedly changed and the hash recalculated until the result meets the current target.

Our 00 condition from Episode 1 was a simplified representation of this process.

Change nonce
↓
Calculate SHA-256
↓
Target met?Bitcoin actually applies SHA-256 twice when calculating a block hash. However, the basic principle remains the same.

SHA-256 does not make the data secret. The hash function makes the connection between blocks and the computational work performed verifiable.

2. Cryptographic Key Pairs

When a Bitcoin wallet is created, private and public keys are generated.

The private key begins as a very large random number.

Very large random number
↓
Private keyThe wallet calculates the corresponding public key from the private key.

Private key
↓
Cryptographic calculation
↓
Public keyIn practice, this calculation only works in one direction.

The private key cannot be calculated from the public key.

The private key remains secret inside the wallet. The public key may be disclosed together with a transaction.

Does Bitcoin Use RSA?

RSA is one of the best-known methods of asymmetric cryptography. However, Bitcoin does not use RSA.

Bitcoin uses a method based on elliptic curves. The curve it uses is called secp256k1.

The mathematical details are not necessary for our explanation.

What matters is how the responsibilities are divided:

Private key: Remains secret
Public key: May be publicThe key pair does not encrypt Anna’s Bitcoin.

It ensures that only the wallet with the matching private key can create valid authorization to spend her Bitcoin.

3. Digital Signatures

Anna wants to authorize a Bitcoin transaction.

Her wallet uses the transaction and her private key to do this.

Transaction

private key ↓ Digital signatureThe transaction and the digital signature are sent to the Bitcoin network.

The private key never leaves Anna’s wallet.

A node uses the public key to verify the signature.

Transaction

digital signature
public key ↓ Signature valid or Signature invalidThe digital signature proves that the transaction was authorized using the matching private key.

It does not hide the contents of the transaction.

Why Can’t the Signature Be Copied?

The signature is calculated from the complete transaction.

If the recipient or amount is changed afterward, the signature no longer matches the transaction data.

A signature therefore cannot simply be copied and attached to another transaction.

Bitcoin originally used ECDSA for these signatures. Newer Taproot transactions can use Schnorr signatures.

Both methods perform the same basic task here: the private key creates a signature, which can then be verified using the public key.

Summary

Bitcoin is not encrypted. Its blockchain and the transactions it contains are publicly visible.

The term cryptocurrency refers to the cryptographic methods that make the system verifiable and control who can spend Bitcoin.

Bitcoin is called a cryptocurrency because these cryptographic methods make the system possible and secure it — not because its transactions are encrypted.

Blockchain and Bitcoin Explained in 6 Episodes — Episode 6

Christian Ahrweiler — Tue, 22 Sep 2026 16:57:07 +0000

Episode 6: How Beaver Proof Uses the Bitcoin Blockchain

Episode 6: How Beaver Proof Uses the Bitcoin BlockchainBeaver Proof is a group of apps that can prove that a file or the contents of a webpage already existed at a particular time and have not been changed since.

The group consists of three apps:

Beaver Proof App GroupBeaver File Proof*
Creates proof for files and folders*Beaver Page Proof*
Creates proof for a webpage*Beaver Proof Verifier*
Verifies existing proof*Beaver Proof does not store files or webpages in the Bitcoin blockchain. Instead, it calculates a hash from the data and connects that hash to a Bitcoin block through OpenTimestamps.

The original data remains outside the blockchain. The Bitcoin block serves only as a time reference that can be verified later.

An Example

Anna receives a quotation as a PDF:

Quotation.pdf
Price 2,500 euros
Valid until September 30, 2026She wants to be able to prove later that this exact quotation already existed today and has not been changed since.

The file’s creation date is not sufficient:

Quotation.pdf
Created on August 30, 2026This date is managed by Anna’s computer and could be changed afterward.

Anna therefore needs a time reference that she does not control herself.

Beaver File Proof provides this by using the Bitcoin blockchain.

The File Hash

Anna drops the quotation onto Beaver File Proof.

The app first calculates the hash of the file:

Quotation.pdf
↓
Calculate hash
↓
Hash of the quotationThe hash is determined by the contents of the file.

This allows Beaver Proof to determine later whether exactly the same file is still present.

As long as the quotation remains unchanged, it produces the same hash. If even a small part of the file were changed, it would produce a different hash.

Original quotation 3dcdff
Modified quotation 2deded### Why Is the Hash Alone Not Enough?

Anna could store the hash together with the current date on her computer:

Hash 3dcdff
Date August 30, 2026However, this would not be independent proof.

Anna could have entered both the hash and the date at a later time. Another person would have to trust her claim that the information was actually created on the stated date.

The hash must therefore be connected to an event that can be publicly verified and cannot later be changed by Anna.

This event is the inclusion of a Bitcoin transaction in a valid block.

The File Remains with Anna

Beaver Proof does not send the complete quotation to Bitcoin.

Only the hash is used for the proof.

The contents of the quotation cannot be reconstructed from the hash.

Other participants therefore learn neither the price, the file name, nor the contents of the document.

OpenTimestamps

Beaver Proof uses OpenTimestamps to connect the hash to the Bitcoin blockchain.

OpenTimestamps collects hashes from many different files and data sets and combines them into one common hash.

Hash of file 1
Hash of file 2
Hash of file 3
Hash of file 4
↓
One common hashThis final hash is anchored as a small piece of verification data in a Bitcoin transaction — usually in a special transaction output called OP_RETURN.

Once the transaction becomes part of a valid block, the verification data becomes part of the verifiable state of the Bitcoin blockchain.

How Are the Hashes Combined?

Two hashes are combined, and a new hash is calculated from them:

Hash 1 + Hash 2
↓
Combined hash AThe same process is applied to the next two hashes:

Hash 3 + Hash 4
↓
Combined hash BThe two new hashes are then combined as well:

Combined hash A

combined hash B ↓ Common final hashThis structure is called a Merkle tree.

The process can continue with thousands of additional hashes. In the end, one common final hash always remains.

Many file hashes
↓
Several intermediate hashes
↓
One common final hashOpenTimestamps connects the common final hash to a Bitcoin transaction.

Once the transaction has been stored in a valid block, the final hash becomes part of the verifiable state of the Bitcoin blockchain.

Because the hash of Anna’s quotation was included in the calculation of the final hash, Anna’s file is now anchored as well.

The file itself still exists only with Anna. Bitcoin contains only the common hash of many files.

The OTS File

For the proof, Beaver File Proof creates a small file with the .ots extension.

Quotation.pdf
Quotation.pdf.otsThe OTS file contains the verification information required to trace the path from the hash of the quotation to its Bitcoin anchoring.

Hash of the quotation
↓
Intermediate hashes
↓
Common final hash
↓
Bitcoin transaction
↓
Bitcoin block### Verifying the File

Beaver Proof Verifier first calculates the hash of the submitted file.

Quotation.pdf
↓
Calculate hash
↓
Current file hashThe app compares this hash with the file hash from the OTS file.

Current file hash
↓
Compare with the hash
from the OTS fileIf both hashes match, the file is unchanged.

If they do not match, the submitted file is no longer exactly the file for which the proof was created. Verification stops.

Only if the file is unchanged does Beaver Proof Verifier proceed to verify its time anchoring in the Bitcoin blockchain.

Querying the Bitcoin Explorer

Beaver Proof Verifier now needs the data from the Bitcoin block in which the common final hash was anchored.

For this purpose, the app queries the Bitcoin explorer Blockstream.info.

The Bitcoin blockchain is stored by the network’s nodes. Its data is public but is not presented in a form that is easy for people to read.*A Bitcoin explorer is a website or service that queries this data and presents it in a readable form.*The OTS file contains the information identifying the Bitcoin block required for the proof.

OTS file
identifies the Bitcoin block
↓
Beaver Proof Verifier
queries Blockstream.info
↓
Blockstream.info returns
the block dataThis block data includes:

Block number
Block hash
Merkle root
TimestampThe Merkle root is the common hash of all transactions in the block. Because the OpenTimestamps anchoring belongs to one of these transactions, the calculation path in the OTS file leads to this Merkle root.

The Decisive Comparison

Beaver Proof Verifier now has two values:

Calculated from the OTS file
Merkle root ARetrieved from the Bitcoin explorer
Merkle root BThe app compares these two values.

Calculated Merkle root
↓
Compare with the Merkle root
of the Bitcoin block
↓
Both values matchIf they match, this proves that the file hash belongs to this Bitcoin block through the OpenTimestamps anchoring.

Only then does Beaver Proof Verifier read the block’s timestamp.

File hash matches
↓
OTS calculation path matches
↓
Block Merkle root matches
↓
Use the block timestampIf every check is successful, the app can display:

File unchanged
Bitcoin anchoring confirmed
Existed no later than
August 30, 2026 at 2:32 PMThe proof does not result merely from Blockstream.info returning a timestamp. The decisive point is that the Merkle root calculated by Beaver Proof Verifier matches the Merkle root actually stored in the Bitcoin block.

Blockstream.info provides the publicly available block data. Beaver Proof Verifier performs the decisive comparison itself.

What Does the Bitcoin Timestamp Prove?

The Bitcoin block provides the independent time reference.

If the hash of Anna’s quotation is verifiably connected to this block, it follows that:

*The quotation must already have existed no later than the time of this Bitcoin block.*The time recorded in a Bitcoin block is not an official timestamp accurate to the exact second. However, it provides a publicly verifiable time before which the file must already have existed.

The proof shows that the file existed no later than the confirmed Bitcoin time.

The Beaver Proof App Group at a Glance

Beaver File Proof

Beaver File Proof creates proof for files or complete folders.

Select file or folder
↓
Create proof package
↓
Anchor hash in time
↓
Include verification dataThe proof package keeps the data to be verified together with its associated verification information.

It can be archived or shared with another person.

Beaver Page Proof

Beaver Page Proof uses the same principle for webpages.

A webpage can change at any time:

Price is changed
Description is replaced
Offer is removed
Webpage disappearsBeaver Page Proof therefore first creates a local capture of the webpage.

Current webpage
↓
Local capture
↓
Calculate hash
↓
Bitcoin timestampIt can later be verified that this exact stored capture remained unchanged and existed no later than the confirmed Bitcoin time.

Beaver Proof Verifier

Beaver Proof Verifier checks an existing proof package.

Open proof package
↓
Verify file hash
↓
Verify OTS proof
↓
Verify Bitcoin anchoringVerification is based on the file being checked, the OTS verification information, and its connection to the Bitcoin blockchain.

The Beaver Proof website:

https://beaverproof.com/

All apps in the App Store:

Beaver Page Proof

Beaver File Proof

Beaver Proof Verifier

Publish One Article Across Your Networks — From Your Mac

Christian Ahrweiler — Tue, 22 Sep 2026 16:54:04 +0000

Publish One Article Across Your Networks — From Your Mac### Beaver Publisher brings articles from Medium, Substack, WordPress, Ghost, DEV and RSS into one publishing workflow.

Publishing an article is often only the beginning.

The original post may live on Medium, WordPress or Substack. After that, its link still needs to be shared on Threads, Bluesky, Mastodon and other networks. A complete copy might also be published on DEV.

Doing this manually means opening several websites, copying the same information repeatedly and remembering where the article has already been posted.

Beaver Publisher brings that workflow into one native Mac app.

Start with the platform you already use

Beaver Publisher does not introduce another place where articles have to be written.

Instead, it reads articles from existing publishing sources:

Medium
Substack
WordPress
Ghost
DEV Community
RSS and Atom feeds Connected sources are synchronized when the app starts. New articles are added to a local library and displayed in reverse chronological order.

Each entry shows its source and publishing status, making it easy to see which articles still need to be distributed.

For platforms that expose a complete API, Beaver Publisher can retrieve the available article history. A Medium export can also be imported to supplement the limited number of posts available through its public feed.

Select an article and choose its destinations

Selecting an article opens its preview together with an editable social post.

Configured publishing targets are shown beside their current status. Beaver Publisher supports:

Threads
Bluesky
Mastodon
Mu, Eurosky and other AT Protocol services
DEV Community Target selections are remembered for each source.

For example, Medium articles can normally be sent to Threads, Bluesky, Mastodon and DEV, while articles originating on DEV can use a different set of destinations.

Publish only where necessary

The Publish button sends the selected article only to destinations where it has not already been published.

Successful publications are recorded locally. Previously completed targets are skipped automatically, reducing the risk of accidentally posting the same article twice.

If one service fails, the remaining destinations can still complete. The failed target remains available for another attempt.

A separate publication history lists successful API publications and provides a direct link to the resulting post whenever the network returns one.

Copy complete formatted articles

Not every publishing platform provides a suitable public API.

The Copy formatted article button places the article on the macOS clipboard with its formatting intact. Compatible editors can retain:

Headings
Paragraphs
Lists
Bold and italic text
Links The same clipboard entry also contains a standard text representation for applications that do not support formatted content.

Beaver Publisher does not automatically open another website and does not claim that a manually copied article has been published. Publication history contains only posts that the app successfully sent through an API.

Your accounts connect directly

Beaver Publisher is not another hosted social media service.

Users connect their own source and target accounts with the credentials or API keys supplied by each platform. Multiple accounts for the same service can be configured.

Secrets are stored in the macOS Keychain. Articles, account settings, target selections and publication history remain locally on the Mac.

Content is sent directly to the selected platform. It is not routed through a Beaver Publisher server.

There is no subscription.

A focused alternative to a recurring publishing service

Large social media management platforms are useful for teams that need scheduling, approval workflows, analytics and cloud collaboration.

Many independent publishers need something simpler:

Publish an article on their preferred platform.
Open it in a local library.
Select the relevant networks.
Publish the remaining links.
Continue writing. Beaver Publisher is designed specifically for that workflow.

One article. Several channels. One clear publishing status.

Beaver Publisher is part of the Beaver Tools collection of focused macOS utilities.

The Beaver Tools - Mac utilities that just work.

AppStore: https://apps.apple.com/us/app/beaver-publisher/id6801988498

Blockchain and Bitcoin Explained in 6 Episodes — Episode 5

Christian Ahrweiler — Wed, 16 Sep 2026 15:45:59 +0000

Episode 5: How Do Digital Signatures Work?

Episode 5: How Do Digital Signatures Work?### How a Bitcoin Wallet Works

In Episode 3, we used a simplified representation of Anna’s wallet:

Anna’s wallet
Bitcoin 1.0 BTCThat was sufficient to explain a Bitcoin payment.

Now we take a closer look: How does Bitcoin get into Anna’s wallet — and how can Anna spend it again?

Anna Creates a Wallet

When Anna creates her wallet, a key pair and an associated Bitcoin address are generated.

Anna’s wallet
Bitcoin address
Public key
Private keyEach component has its own purpose:

Bitcoin address Receive Bitcoin
Private key Sign a transaction
Public key Verify a signatureAnna can share her Bitcoin address.

The private key remains in her wallet and must never be shared with anyone.

Anna Receives Bitcoin

Anna gives Anne her Bitcoin address.

Anne uses this address as the recipient of a transaction:

New transaction
Amount 1.0 Bitcoin
Recipient Anna’s Bitcoin addressAfter the transaction has been verified and stored in a block, the blockchain contains an available amount for Anna’s address:

Available amount
Address Anna’s Bitcoin address
Amount 1.0 BitcoinAnna’s wallet recognizes that this address belongs to it and displays the amount:

Anna’s wallet
Bitcoin 1.0 BTCThe Bitcoin was not transferred to Anna’s device as a file. The amount remains recorded in the blockchain.

The wallet displays it because it manages the associated address and the corresponding keys.

Anna Wants to Spend Bitcoin

Anna now wants to send 0.3 Bitcoin to Paul.

Her wallet creates a new transaction:

New transaction
Uses 1.0 Bitcoin from Anna
To Paul 0.3 Bitcoin
Back to Anna 0.6999 Bitcoin
Fee 0.0001 BitcoinBefore the network can accept this transaction, it must answer one question:

*Was the transaction authorized by the wallet that belongs to Anna’s address?*Anna’s wallet uses the private key for this purpose.

The Digital Signature

Anna’s wallet uses the transaction and her private key to calculate a digital signature.

Transaction

private key ↓ Digital signatureThe signature is valid only for this exact transaction.

Anna’s wallet then sends the following information to the Bitcoin network:

Transaction
Digital signature
Public keyThe private key is not transmitted. It remains in Anna’s wallet.

The First Check

The Bitcoin was previously sent to Anna’s address.

The node must therefore first verify that the included public key belongs to this address.

There is a verifiable connection between Anna’s public key and her Bitcoin address. In simplified terms, the address is created from a hash of the public key.

Public key
↓
Calculate hash
↓
Bitcoin addressThe node performs this calculation itself.

Included public key
↓
Calculate Bitcoin address
↓
Compare with the existing addressIf the addresses match, the node knows:

This public key belongs to the address to which the amount was assigned.### The Second Check

The node now uses the public key to verify the digital signature.

Transaction

digital signature
public key ↓ Verify signatureIf the signature is valid, the node knows:

*The wallet containing the associated private key authorized this transaction.*Both necessary connections have now been verified:

Public key
belongs to Anna’s address
↓
Digital signature
belongs to the transaction
↓
Anna may spend the amount### Two Keys That Belong Together

The private key and public key form a key pair.

The public key can be used to verify a signature. A new signature can only be created with the private key.

The private key cannot be calculated from the public key. Anna’s wallet can therefore send the public key together with the transaction without revealing the private key.

This method of using two different but related keys is called asymmetric cryptography.

Is There a Key Server?

Bitcoin does not require a key server or a central directory of public keys.

When Anna receives Bitcoin, she shares only her Bitcoin address:

Receive Bitcoin
Anna shares her addressWhen she later spends the amount, her wallet sends the public key and digital signature with the transaction:

Spend Bitcoin
Public key is included
Digital signature is includedEvery node can perform the necessary checks independently.

A Wallet Can Have Many Addresses

For our explanation, we use only one address and one key pair.

A modern wallet can manage multiple addresses and their associated keys.

Anna’s wallet
Address 1 Key pair 1
Address 2 Key pair 2
Address 3 Key pair 3The wallet determines the available amounts belonging to all of its addresses and displays the total to Anna.

What Happens If the Wallet Is Lost?

If Anna’s device breaks, the Bitcoin does not disappear. The amounts remain recorded in the blockchain.

However, Anna needs her private keys to spend those amounts.

When a wallet is created, it therefore usually displays a sequence of twelve or 24 words. This is called a recovery phrase or seed phrase.

A wallet can derive its keys and addresses again from this phrase.

Recovery phrase
↓
Restore keys
↓
Restore accessAnyone who possesses the recovery phrase can restore the wallet on another device and spend the associated Bitcoin.

There is no central authority that can reset a lost recovery phrase.

Signing Is Not Encryption

Encryption is intended to hide content.

A digital signature is intended to prove that specific data was authorized with the corresponding private key.

Bitcoin transactions are not normally secret. They are distributed across the network and stored in the public blockchain.

The digital signature does not hide the transaction. It allows the nodes to verify that the wallet containing the corresponding private key authorized the transaction.

We now know what Anna’s wallet actually does: It manages the addresses and keys that allow Anna to receive and spend Bitcoin.

In Episode 6, we see how Beaver Proof uses the Bitcoin blockchain to prove that a file already existed at a particular time and has not been changed since.

Blockchain and Bitcoin Explained in 6 Episodes — Episode 4

Christian Ahrweiler — Wed, 16 Sep 2026 15:10:01 +0000

Episode 4: Bitcoin: History, Mining, and the Future

Episode 4: Bitcoin: History, Mining, and the Future*In Episode 3, we saw how Bitcoin uses blockchain technology: Transactions are collected, verified, and stored in blocks. The nonce is then changed repeatedly in search of a hash that meets the required condition.*Now we look at Bitcoin itself: Where did it come from? Why would anyone participate in mining? How much computing power and energy does the network require? And what happens when no new Bitcoin is created?

The Beginning

On October 31, 2008, a nine-page document titled “Bitcoin: A Peer-to-Peer Electronic Cash System” was published.

The author was identified as Satoshi Nakamoto.

To this day, nobody knows who is behind this name. It may have been one person or a group of people.

On January 3, 2009, the Bitcoin blockchain began with its genesis block. A few days later, the first transfer of Bitcoin between two people took place: Satoshi Nakamoto sent ten Bitcoin to programmer Hal Finney.

Bitcoin did not belong to Satoshi Nakamoto, however. Its source code was published and could be run, examined, and developed further by other people. There was no central server and no single operator controlling the network.

Satoshi Nakamoto later withdrew from the project. Bitcoin continued to operate without its creator.

What Is One Bitcoin Worth Today?

Bitcoin does not have a fixed price. Its price is determined by supply and demand on trading platforms and can change within minutes.

On August 30, 2026, one Bitcoin (BTC) was worth approximately 78,000 US dollars. This figure is therefore only a snapshot. Current Bitcoin price

Transaction volume also fluctuates. At the end of August 2026, the Bitcoin blockchain confirmed approximately 600,000 to 800,000 transactions per day. Bitcoin worth several billion US dollars was transferred each day. Current network data

These figures describe only transactions stored directly in the blockchain. Payments made through additional systems such as the Lightning Network are not fully included.

Why Would Anyone Participate in Mining?

In Episode 3, we looked at mining from the perspective of the blockchain: A suitable nonce must be found for every new block.

But why would miners use their equipment and electricity to do this?

Anyone who finds a valid block may include a special transaction that assigns the specified reward to them.

The miner cannot choose the amount. It is determined by the Bitcoin rules and verified by every node.

Reward for one block
New Bitcoin 3.125 BTC
Transaction fees Variable*At a Bitcoin price of approximately 78,000 US dollars, the 3.125 newly created Bitcoin alone are worth around 244,000 US dollars.That sounds like an enormous profit. However, one single computer does not find a block every ten minutes. A very large number of specialized computers compete with one another around the world. They consume large amounts of electricity and usually find nothing.Many operators therefore combine their computing power in a mining pool. If the pool finds a block, the reward is distributed among its participants according to the computing power they contributed.**The approximately 244,000 US dollars are therefore the revenue from one successfully found block — not automatically the profit of one operator. Electricity, equipment, cooling, and operating costs must still be paid.*The newly created Bitcoin is called the block subsidy. It is supplemented by the fees paid by the transactions included in the block.

Only the combination of these activities fully explains mining:

Collect transactions
↓
Verify transactions
↓
Search for a suitable nonce
↓
Publish a valid block
↓
Receive the rewardMining therefore does not simply mean creating new Bitcoin. It means calculating new blocks and thereby continuing the blockchain.

New Bitcoin is currently part of the reward. It is not the actual purpose of mining.

How Many Bitcoin Can Exist?

The number of new Bitcoin created per block is defined by the Bitcoin rules.

The block subsidy initially amounted to 50 Bitcoin. It is cut in half after every 210,000 blocks. This happens approximately every four years and is called the halving.

2009 50 BTC per block
2012 25 BTC per block
2016 12.5 BTC per block
2020 6.25 BTC per block
2024 3.125 BTC per blockThese repeated halvings cause the total amount created to approach a fixed limit: Slightly fewer than 21 million Bitcoin can exist.

More than 20 million of them have already been created.

The block subsidy continues to become smaller but will not effectively reach zero until around the year 2140. The final Bitcoin is therefore not created in one last major discovery. The newly created amount becomes progressively smaller over many decades.

How Much Work Does Mining Require?

In our simplified example, the hash had to begin with 00. Only a small proportion of all possible hashes met this condition.

The condition in Bitcoin is far more difficult. At the end of August 2026, only about one out of every

540,000,000,000,000,000,000,000 hashesmet the required condition on average.

That is approximately 540 sextillion attempts.

Every attempt consists of the same steps:

Insert nonce
Calculate hash
Check conditionIf the hash does not meet the condition, the nonce is changed and the next hash is calculated.

A suitable hash may be found by chance on the very first attempt. It may also take more than 540 sextillion attempts. The figure describes only the average across a very large number of successfully found blocks.

The difficulty of the current condition is described by Bitcoin’s difficulty. The higher the difficulty, the smaller the proportion of hashes that meet the condition — and the more attempts are required on average.

The logical sequence is:

More difficult condition
↓
Fewer hashes meet it
↓
More attempts on average
↓
Higher difficultyIn our simplified example, the hash had to begin with 00.

Bitcoin’s actual rule is not “The hash must begin with a certain number of zeros.” Instead, the hash, interpreted as a number, must be smaller than a specified target value.

This value is called the mining target, or simply the target. How difficult it is to reach this target is described by the mining difficulty.

The principle remains the same:

Block data and nonce
↓
Calculate hash
↓
Does the hash meet the target?
↓
No: Change nonce and calculate again
Yes: Publish blockAll computers participating in Bitcoin mining currently perform a combined total of approximately one quintillion hash calculations per second.

Despite the enormous difficulty, this allows the complete network to find a valid block approximately every ten minutes on average. Current hashrate and difficulty

Why Does It Remain Close to Ten Minutes?

When more computers participate in mining, suitable hashes are initially found more quickly. When computers are switched off, the search takes longer.

Bitcoin therefore adjusts the difficulty after every 2,016 blocks. This happens approximately every two weeks.

If the previous blocks were found too quickly, the condition becomes more difficult. If they were found too slowly, it becomes easier.

More computing power
↓
Blocks are found more quickly
↓
Difficulty increases
↓
Back to approximately 10 minutes per blockThis prevents the speed of the blockchain from depending permanently on the number of computers participating in mining.

Why Does Bitcoin Require So Much Energy?

A single hash calculation requires very little energy. Bitcoin mining, however, performs an unimaginable number of hash calculations every second.

Specialized devices operate around the clock to perform these calculations. The computers require electricity and produce heat. Cooling systems and other technical equipment also consume energy.

The total energy requirement cannot be measured precisely because the equipment is distributed across many countries and operators. Studies from Cambridge estimate annual electricity consumption at approximately 140 to 180 terawatt-hours, depending on the calculation method. That is roughly equivalent to Poland’s annual electricity consumption.

This is an estimate, not a direct meter reading. The actual consumption depends on factors including the equipment being used, the total computing power, and electricity prices. Cambridge Bitcoin Electricity Consumption Index

This effort is not an unintended side effect. It is part of the Proof-of-Work security model.

Creating a valid block is intended to be expensive. Verifying the same block remains easy.

A node does not have to test trillions of nonces itself. It uses the nonce included in the block, calculates the hash once, and checks whether it meets the target.

Does Every Transaction Consume That Much Energy?

The energy consumption of mining cannot meaningfully be divided by the number of transactions.

The computers search for a valid block regardless of whether that block contains only a few transactions or many. One additional payment therefore does not automatically cause a corresponding number of additional mining devices to be switched on.

The energy is used to create and secure the blocks. It is not directly determined by the number of transactions.

What Happens After the Last Bitcoin?

Mining does not end when no new Bitcoin is created.

Only the first part of the reward disappears:

Reward today
New Bitcoin 3.125 BTC
Transaction fees VariableReward in the future
New Bitcoin 0 BTC
Transaction fees VariableAnyone who finds a block will then receive only the fees from the transactions included in it.

The blockchain can therefore continue without the creation of new Bitcoin. The crucial question is whether transaction fees will be sufficient to finance enough computing power in the future.

Nobody can answer this with certainty today. Bitcoin relies on network usage and the demand for limited space inside its blocks to generate sufficient fees.

What About Small Payments?

A small payment made directly through the Bitcoin blockchain can become impractical if the fee is too high in relation to the amount being sent.

The Lightning Network was developed in part to address this problem.

Two participants can open a payment channel with a normal Bitcoin transaction. A very large number of small payments can then take place inside that channel without each one being written into its own Bitcoin block.

Only when the channel is closed is the final combined result recorded in the blockchain.

Open channel Bitcoin transaction
Many small payments Outside the blockchain
Close channel Bitcoin transactionLightning makes small and fast payments possible without permanently storing every individual payment in the Bitcoin blockchain.

The individual Lightning payments do not pay miners directly. Miners receive fees only from the transactions used to open, close, or settle a disputed channel.

Small payments can therefore help keep Bitcoin usable as a payment system. The long-term financing of mining must still come from fees paid for the limited space in the actual blockchain.

What Makes Bitcoin Special?

Bitcoin is not operated by a company. There is no central database, no board of directors, and no single computer whose shutdown would end the system.

Instead, several mechanisms work together:

Blockchain Connects the blocks
Nodes Verify the rules
Proof of Work Makes blocks expensive to create
Mining Continues the chain
Difficulty Regulates the computational effort
Rewards Finance mining
Limited supply Controls the creation of new BTCBitcoin is therefore more than a digital currency. It is a system in which many independent participants can reach a common, verifiable state without having to trust a central authority.

We have deliberately simplified one crucial question:

How does the network know that a transaction was really authorized by Anna?

Bitcoin uses digital signatures for this purpose. Episode 5 explains how they work.

Capture an Entire Webpage in Safari with One Click

Christian Ahrweiler — Tue, 15 Sep 2026 15:13:13 +0000

Capture an Entire Webpage in Safari with One Click### Save long webpages as one clean PNG — without stitching screenshots manually

A normal screenshot captures only what is currently visible on the screen. That works for dialogs, images, and small sections, but not for complete articles, documentation pages, receipts, dashboards, or other long webpages.

Capturing the rest usually means scrolling, taking several screenshots, and joining them manually.

Beaver Full Screenshot adds a simpler option directly to Safari:

One click. The complete webpage. One PNG.

Full-page screenshots directly from Safari

After enabling the Safari extension, open a regular webpage and click the Beaver Full Screenshot button in the toolbar.

The extension then:

scrolls through the complete page
captures every visible section
combines the sections into one PNG
restores the original scroll position
saves the finished screenshot locally There is no area selection, editor, account, or complicated capture workflow. The toolbar button performs one clearly defined task.

Useful for more than articles

Full-page screenshots can be useful for:

archiving online receipts and confirmations
saving complete articles for reference
documenting website changes
capturing product and landing pages
recording dashboards and reports
reviewing long pages with clients
preserving documentation or support content
creating visual website records Instead of managing several disconnected images, the complete page remains together in one file.

Designed for privacy

Webpages and screenshots can contain private or sensitive information. Beaver Full Screenshot therefore performs the capture and image processing locally on the Mac.

No account
No subscription
No cloud processing
No analytics or tracking The captured webpage remains on the device.

Why is there a separate app?

Safari extensions are distributed inside Mac apps. The small Beaver Full Screenshot app installs the extension and provides a button for opening Safari’s extension settings.

The setup is required only once:

Install and open Beaver Full Screenshot.
Enable the extension in Safari.
Add its button to the Safari toolbar.
Close the app. The containing app does not need to remain running. After activation, the extension works directly inside Safari.

A focused Safari utility

Many screenshot applications include annotations, cloud sharing, workspaces, accounts, and subscriptions. Those features can be useful — but they also add steps when the only goal is to save a complete webpage.

Beaver Full Screenshot deliberately stays focused:

Open a page. Click the button. Get one PNG.

Download Beaver Full Screenshot from the Mac App Store

More Beaver Tools: https://beavertools.app/

Turn Your Articles Into Podcast Episodes

Christian Ahrweiler — Tue, 15 Sep 2026 15:11:06 +0000

Turn Your Articles Into Podcast Episodes### Beaver Publisher now converts written posts into narrated audio and publishes them through podcast hosts

An article does not have to remain an article.

Some people prefer reading. Others listen while driving, walking, exercising, or working. Reaching both audiences traditionally means producing the same content twice: once as a written post and again as a recorded podcast episode.

Beaver Publisher can now turn an existing article into a narrated podcast episode.

The article remains the source. Beaver Publisher prepares its text for narration, ElevenLabs generates the audio, and the finished episode can be published through Transistor or RSS.com.

From Written Post to Spoken Episode

The process begins with an article already available in Beaver Publisher.

Instead of recording the entire text manually, you can convert it into audio using your own ElevenLabs account. Beaver Publisher sends the narration text to the selected ElevenLabs voice and receives the finished audio.

You remain in control of the voice and the account being used. Beaver Publisher does not bundle a shared AI subscription or hide usage behind its own service. You connect your personal ElevenLabs API key.

This also means you can use the voices and models available with your ElevenLabs plan — including a voice chosen specifically for English, German, or another supported language.

Publishing to a Podcast Host

Apple Podcasts and Spotify do not normally receive each new episode directly from publishing software.

Instead, podcast directories follow an RSS feed provided by a podcast host. When the host adds a new episode to that feed, connected podcast apps discover it automatically.

That makes the podcast host the actual publishing destination.

Beaver Publisher currently supports two such destinations:

Transistor
RSS.com Connect your existing host account using its API credentials, select the podcast show, and publish the generated episode.

The podcast host stores the audio file, updates the show’s RSS feed, and distributes the new episode to the directories connected to that feed.

Bring Your Own Accounts

Beaver Publisher connects the services required for the workflow without becoming another subscription platform itself.

You provide:

an ElevenLabs API key for text-to-speech
a Transistor or RSS.com account for podcast hosting Your podcast remains with your chosen host. Its RSS feed remains the point of distribution, and the host continues to provide its normal website, player, statistics, and directory connections.

Beaver Publisher handles the path from the source article to the published episode.

More Than Cross-Posting

Beaver Publisher began as a way to maintain one article source and distribute new posts to several networks.

Audio publishing extends that idea beyond copying the same text to another website.

The content is transformed into another medium.

A written article becomes something people can listen to. The original post provides the source and reference link. The podcast episode opens another channel without requiring the author to write or record the entire story again.

One article can now become a web publication, a social post, and a podcast episode — all from the same source.

Discover Beaver Publisher and more focused macOS tools at Beaver Tools.

Download on AppStore: https://apps.apple.com/us/app/beaver-publisher/id6801988498

Blockchain and Bitcoin Explained in 6 Episodes — Episode 3

Christian Ahrweiler — Mon, 14 Sep 2026 21:22:50 +0000

Episode 3: Bitcoin as an Application of Blockchain Technology

Episode 3: Bitcoin as an Application of Blockchain Technology*In the first two episodes, we explained how a blockchain is built, secured, and stored across many independent nodes.*Now we look at a practical application of this technology: Bitcoin.

Bitcoin has its own blockchain, its own network, and its own rules.

The data blocks in this blockchain store Bitcoin transactions.

What Is a Bitcoin Wallet?

To use Bitcoin, you need a wallet — something similar to a purse or a physical wallet.

A wallet is an app or a small device that allows you to receive, hold, and send Bitcoin.

It displays the available amount and provides basic functions similar to those of a banking app:

Receive Bitcoin
Display the available amount
Send Bitcoin
Display previous payments For now, we can imagine that the Bitcoin is stored directly in the wallet.

Anna has 1.0 Bitcoin in her wallet and wants to send 0.3 Bitcoin to Anne.

Anna’s wallet
Available 1.0 Bitcoin
Send 0.3 Bitcoin
Recipient AnneAnna confirms the payment. Her wallet creates a Bitcoin transaction and sends it to the Bitcoin network.

How Does a Wallet Receive Bitcoin?

Every wallet can generate a receiving address.

This address can be shared like a bank account number. Anyone who wants to send Bitcoin to Anna enters Anna’s receiving address as the destination of the transaction.

Payment to Anna
Recipient Anna’s Bitcoin address
Amount 1.0 BitcoinThe address does not contain a name and does not automatically reveal who owns it.

Anna can also use multiple receiving addresses. The wallet manages these addresses and combines the associated amounts into one displayed balance.

Where Is the Bitcoin Actually Stored?

The idea that the Bitcoin is stored directly in the wallet is helpful — but technically, it is not entirely correct.

A banking app does not contain the euros in a bank account either. It only displays the balance and provides access to it.

With Bitcoin, there is no central bank. The information about the available amounts is stored in the Bitcoin blockchain.

The wallet reads this information and shows Anna the amount she can use.

The wallet also manages secret information that allows it to digitally authorize a payment for Anna.

How this authorization works is not yet important for understanding the next steps. What matters for now is:

Only Anna’s wallet can authorize the use of her Bitcoin.
The secret information is not published.
Other participants can still verify that the authorization is valid.
Changing the payment afterward would invalidate the authorization. The wallet therefore does not contain the Bitcoin itself. It manages access to the amounts recorded in the blockchain.

How Does Bitcoin Store an Amount?

The Bitcoin blockchain does not contain a simple list of account balances:

Account balances
Anna 1.0 Bitcoin
Anne 0.5 BitcoinInstead, it contains transactions.

An earlier transaction may have established that Anna can use an amount of 1.0 Bitcoin:

Earlier transaction
Available amount 1.0 Bitcoin
Available to AnnaAs long as Anna has not transferred this amount, it is considered unspent.

Bitcoin calls such an available amount an Unspent Transaction Output, or UTXO.

This simply means:

*A UTXO is an amount from an earlier transaction that has not yet been transferred.*The wallet finds the available amounts that Anna can use, adds them together, and displays the result as her balance.

Anna Pays Anne

Anna wants to send 0.3 Bitcoin from her available amount of 1.0 Bitcoin to Anne.

Her wallet creates a new transaction.

A Bitcoin transaction does not simply subtract 0.3 Bitcoin from a stored account balance. It uses an existing amount in full and creates new available amounts from it.

New transaction
Uses 1.0 Bitcoin from Anna
To Anne 0.3 Bitcoin
Back to Anna 0.6999 Bitcoin
Fee 0.0001 Bitcoin
Authorization by Anna’s walletThe original amount of 1.0 Bitcoin is now considered spent.

In its place, two new available amounts are created:

New available amounts
0.3 Bitcoin for Anne
0.6999 Bitcoin for AnnaThe amount returned to Anna is called change.

This is similar to paying with cash. If someone uses a 10-euro note to buy an item for 3 euros, the complete note is spent and 7 euros is returned as change.

The small remaining amount of 0.0001 Bitcoin is the transaction fee.

The Wallet Authorizes the Transaction

Before sending the transaction, the wallet adds a digital authorization.

This authorization belongs specifically to this transaction.

If the amount or recipient were changed afterward, the authorization would no longer be valid.

Other participants can verify the authorization without knowing Anna’s secret information.

For understanding the rest of the process, the following is sufficient for now:

*Anna’s wallet can clearly authorize a payment without revealing its secret information.*We explain how this is technically possible separately in Episode 5.

The authorized transaction is now sent to the Bitcoin network.

The Nodes Verify the Transaction

The nodes do not accept Anna’s transaction without checking it.

Among other things, they verify:

Does the amount being used exist?
Has this amount not already been spent?
Is the digital authorization valid?
Do the newly created amounts match the amount being used?
Does the transaction follow all the rules of the Bitcoin network? If any of these conditions is not met, the transaction is rejected.

If the transaction is valid, the node initially stores it as a waiting transaction and forwards it to other nodes.

This is how the transaction spreads across the Bitcoin network.

Must a Node Search the Entire Blockchain?

No.

As explained in Episode 2, a fully synchronized node has already verified the Bitcoin blockchain from its first block onward.

During this verification, it created a current list of all amounts that have not yet been spent.

This list is called the UTXO set.

Currently available amounts
1.0 Bitcoin for Anna
0.5 Bitcoin for Anne
2.0 Bitcoin for another ownerWhen Anna’s transaction arrives, the node does not have to search the entire blockchain again.

It checks the UTXO set to see whether the amount of 1.0 Bitcoin is still available.

When Anna’s transaction is later added to the blockchain, the node removes the old amount and adds the newly created amounts:

Before the transaction
1.0 Bitcoin for AnnaAfter the transaction
0.3 Bitcoin for Anne
0.6999 Bitcoin for AnnaThe UTXO set is therefore the current state calculated by a Bitcoin node from all previously verified blocks.

This is exactly why a pruned node can delete old block data and still verify new transactions.

Where Does the Transaction Wait?

A valid transaction is not automatically part of the Bitcoin blockchain.

It is first placed in storage for waiting transactions.

This storage is called the mempool.

Every node has its own mempool. The transactions it contains can differ slightly because they arrive at different nodes at different times.

Waiting transactions
Anna sends 0.3 Bitcoin to Anne
Paul sends 0.1 Bitcoin to Maria
Robert sends 0.5 Bitcoin to LisaThe transactions have already been verified, but they are not yet included in a block.

Who now assembles the next block from these waiting transactions?

The Miners

This task is performed by miners.

A miner is a participant in the Bitcoin network that assembles a possible new block from waiting transactions.

The miner selects transactions from its mempool and combines them into a block.

Possible new block
Previous hash Hash of the latest Bitcoin block
Transactions Selected transactions
Nonce Not yet found
Hash Condition not yet metAt first, this block is only a candidate.

Before it can be appended to the Bitcoin blockchain, its hash must meet the current Proof-of-Work condition.

What Does Mining Mean?

Mining is the search for a suitable nonce for a new Bitcoin block.

The selected transactions and the other properties of the block have already been determined. The nonce is now changed and the block’s hash recalculated repeatedly until the difficulty target is met — just like our 00 condition from Episode 1.

Mining
Nonce 1 Condition not met
Nonce 2 Condition not met
Nonce 3 Condition not met
Nonce 4 Condition not met
…
Nonce 8,245,912 Condition metIn the real Bitcoin blockchain, the condition is far more difficult. An enormous number of possibilities are therefore tested worldwide.

All participating miners work simultaneously on a possible new block.

Mining is not the process of solving a complicated mathematical problem. It is the extremely fast testing of many possibilities until a hash happens to meet the required condition.

Why Does a Block Take About Ten Minutes?

The more computing power participates in the search, the faster a suitable nonce would normally be found.

Bitcoin therefore adjusts the difficulty of the condition regularly.

If blocks are found too quickly on average, the condition becomes more difficult. If they are found too slowly, it becomes easier.

Over the long term, this results in a new Bitcoin block being found approximately every ten minutes on average.

An individual block may still be found after only a few seconds or take significantly longer than ten minutes. The search is based on chance.

A Miner Finds a Valid Block

When a miner finds a suitable nonce, the complete block is sent to the Bitcoin network.

The other nodes do not accept it automatically.

Every node independently verifies:

Does the block point to the correct predecessor?
Does the block actually produce the stated hash?
Does the hash meet the Proof-of-Work condition?
Are all included transactions valid?
Has any amount been spent twice?
Does the complete block follow the Bitcoin rules? Only if all checks are successful does a node accept the block as valid and add it to its copy of the Bitcoin blockchain.

The included transactions are then removed from the mempool and the UTXO set is updated.

Miners can therefore propose new blocks. They cannot arbitrarily change the rules of the blockchain.

The independent nodes determine whether a published block is valid by verifying it themselves.

What Is a Confirmation?

As soon as Anna’s payment to Anne is included in a valid block, it has one confirmation.

When another block is appended, the transaction has two confirmations.

Confirmations
Block containing Anna’s transaction 1 confirmation
Next block 2 confirmations
Another block 3 confirmationsWith every following block, the amount of Proof of Work building on Anna’s transaction increases.

A confirmation does not mean that a central service approved the payment.

It means that the transaction was included in a valid block.

Further confirmations show how many valid blocks have since been built on top of it.

What Does the Bitcoin Blockchain Store?

The Bitcoin blockchain does not store digital coins or simple account balances.

It stores a chronological chain of valid transactions.

From these transactions, every full node calculates which amounts are currently still unspent.

The wallet displays these amounts and allows its owner to transfer them.

The nodes verify transactions and blocks.

The miners assemble possible new blocks and use Proof of Work to search for a suitable nonce.

Together, these components create a payment system without a central bank and without a single operator controlling the database.

Further Episodes

In Episode 4, we examine the history, current size, and future of Bitcoin — from Satoshi Nakamoto’s white paper to the limit of nearly 21 million Bitcoin.We have deliberately left one technical question unanswered:How can a wallet clearly authorize a transaction without revealing its secret information?We explain this in Episode 5 using private and public keys and digital signatures. Anyone who wants to skip this technical excursion can continue directly with Episode 6: How Beaver Proof uses the Bitcoin blockchain to create verifiable timestamps.

Publish Once. Distribute Everywhere.

Christian Ahrweiler — Mon, 14 Sep 2026 21:20:43 +0000

Beaver Publisher brings articles, social networks, audio, and podcasts together in one Mac app

Publish Once. Distribute Everywhere.Publishing an article is often only the beginning.

After writing it, you may want to share it on Threads, Bluesky, Mastodon, Pinterest, Tumblr, DEV Community, Discord, and several other networks. Then perhaps you want to create an audio version and release it as a podcast episode.

The article stays the same — but every platform requires another login, another browser tab, and another publishing step.

Beaver Publisher brings that workflow into one organized Mac app.

Start With the Articles You Already Publish

Beaver Publisher creates a local article library from your existing publishing sources:

Medium
Substack
WordPress
Ghost
DEV Community
Any RSS or Atom feed Your library synchronizes automatically. Articles appear newest first, together with their source and current publishing status.

If you have been publishing on Medium for years, you can also import older articles from a Medium export instead of being limited to the latest posts in its feed.

There is no need to write everything again in another editor. Beaver Publisher begins with the articles you already have.

Select an Article. Choose the Destinations. Publish.

Connect your own accounts and distribute an article directly to:

Threads
Bluesky
Mastodon
Mu, Eurosky, and other AT Protocol services
DEV Community
Tumblr
Pinterest
Discord
For networks that do not provide a suitable publishing interface, Beaver Publisher prepares the post and opens the appropriate browser workflow:
X
LinkedIn
Facebook
Hacker News
Substack Notes
Select the targets you want and click Publish.

Beaver Publisher checks the article’s publication history and sends it only to selected destinations that have not already received it. This helps prevent the same article from being posted twice by accident.

Each source remembers its selected targets, making repeated publishing workflows much faster.

Turn an Article Into Spoken Audio

An article does not have to remain text.

Connect your own ElevenLabs account, select a voice and model, and Beaver Publisher can turn the article into a spoken MP3.

Before creating the audio, the app shows an estimated cost based on the article length. The request is sent directly to ElevenLabs using your API key, and you pay ElevenLabs directly.

The completed MP3 is stored locally on your Mac. You can play it, download it, or use it for podcast publishing without leaving Beaver Publisher.

Apple system voices are not used.

Publish the Audio as a Podcast Episode

Once the audio has been created, Beaver Publisher can upload it directly to:

Transistor
RSS.com Choose the podcast host, select one of your shows, and publish.

The MP3 becomes the episode audio. If the original article includes an image, Beaver Publisher also sends it as the episode artwork.

Your podcast host then updates the show’s RSS feed. Services such as Apple Podcasts and Spotify read that feed automatically. They are therefore not separate publishing targets inside Beaver Publisher.

The workflow is straightforward:

Select an article.
Create its audio version.
Choose a podcast show.
Publish the episode. A written article can become a podcast episode without manually exporting files and rebuilding the content elsewhere.

Copy the Complete Formatted Article

Some platforms still work best with manual publishing.

For those cases, Beaver Publisher can copy the complete formatted article with a single click. Compatible editors retain headings, paragraphs, lists, emphasis, and links automatically.

This is especially useful when publishing to services that do not offer a practical API or when you want to review the final layout before posting.

See What Has — and Has Not — Been Published

As the number of articles and destinations grows, publication history becomes increasingly important.

Beaver Publisher distinguishes between:

Unpublished articles
Partially published articles
Completed articles You can search the library, filter by source or status, inspect publication history, and open published posts directly.

The social text remains editable for every article, so the accompanying message can be adjusted before it is sent to each network.

The app also provides an HTML preview of the original article, allowing you to review the content without returning to the source website.

One Clear Publishing Workflow

Beaver Publisher is designed around the complete path from an existing article to its different destinations:

Multiple source accounts
Multiple publishing accounts
Automatic article synchronization
Search and source filters
Publication-status filters
Persistent target selections
Editable social-post text
HTML article previews
Publication history
Direct links to published posts
Formatted article copying
ElevenLabs audio creation
Audio playback and download
Podcast publishing through Transistor and RSS.com Instead of keeping a separate checklist for every article, the publishing state remains attached to the article itself.

Your Accounts, Your Content

Beaver Publisher does not operate an intermediary publishing service.

You connect directly to supported platforms using credentials or API keys supplied by those services. The same applies to ElevenLabs: the app uses your own account and API key.

Credentials are stored securely in the macOS Keychain.

Articles, account settings, generated audio, and publication history remain locally on your Mac. Beaver Publisher does not route your content through our servers.

There is no Beaver Publisher subscription.

Publish Once. Distribute Everywhere.

Writing the article should be the creative part.

Distributing it should be an organized, repeatable workflow.

Beaver Publisher keeps your existing articles in one Mac library, tracks where each one has been published, distributes them across multiple networks, and turns written posts into podcast episodes.

One article. Multiple formats. Every destination under control.

Available on the AppStore: https://apps.apple.com/us/app/beaver-publisher/id6801988498

More from The Beaver Tools: https://beavertools.app/

Seal Your Work Before You Deliver It

Christian Ahrweiler — Mon, 14 Sep 2026 21:19:03 +0000

Seal Your Work Before You Deliver It### Preserve the original files before they leave your hands.

A photographer completes a commercial shoot for an agency.

The final selection is edited, exported, and delivered in full resolution. The agency receives everything it needs to begin the campaign.

But the invoice remains unpaid.

A few weeks later, the photographs appear online and in promotional materials. The agency now claims that the images were created internally — or obtained from somewhere else.

The photographer still has the original files, but that alone may not clearly establish when those exact files existed or whether they were subsequently changed.

Fortunately, the complete project was sealed with Beaver File Proof before delivery.

Preserve the complete working set

Before sending the images, the photographer placed the relevant material into one project folder:

Original RAW files
Final edited images
Lightroom or Photoshop project files
Exported delivery files
A short project description
A list of the files supplied to the agency Beaver File Proof sealed the complete folder and created a timestamped, verifiable proof package.

The package confirms that these exact files existed by the confirmed time — and that they have not been modified since they were sealed.

Even the smallest change to a file produces a different digital fingerprint and causes verification to fail.

What the proof can establish

Beaver File Proof does not automatically determine who created a photograph or who owns its copyright.

What it provides is a verifiable point in time for the exact project files.

In this example, the proof can demonstrate that the photographer possessed the original RAW files, working files, and finished exports before the agency published the images.

Combined with contracts, invoices, emails, delivery records, and the later publication date, the sealed package can become an important part of the evidence.

The agency may dispute where the images came from. It cannot change the confirmed timestamp or secretly modify the files inside the proof package.

Not only for photographers

The same workflow applies to many types of original work:

Manuscripts before submission to a publisher
Designs before presentation to a client
Source code before delivery
Music recordings and project files
Research data and reports
Architectural plans
Video productions
Product concepts and prototypes
Contract drafts and important document versions Whenever files leave your control, preserving the exact version beforehand can be valuable.

Your files are not uploaded to the blockchain

Beaver File Proof uses the open OpenTimestamps protocol.

Your photographs, documents, source code, or other private files are not published on the Bitcoin blockchain. The timestamping process uses only a cryptographic fingerprint derived from the sealed package.

The original content remains in your possession.

Anyone can verify the package

A proof becomes more useful when another person can check it.

The separate Beaver Proof Verifier app allows a client, adviser, insurer, lawyer, or other recipient to verify the package for free.

Verification confirms whether the files still match the sealed proof and whether the timestamp has been anchored to the Bitcoin blockchain.

No Beaver account is required.

Preserve first. Deliver second.

Once a file has been shared, copied, edited, or published, reconstructing its earlier state can become difficult.

Beaver File Proof makes the precaution simple:

Collect the original and working files.
Create the proof package.
Wait for the timestamp confirmation.
Store the proof safely.
Deliver or publish the work. If a dispute arises later, the original project state has already been preserved.

Before your work leaves your hands, seal the files.

Get Beaver File Proof on the Mac App Store

Download Beaver Proof Verifier for free

Learn more at beaverproof.com.

Seal the Offer Before You Book

Christian Ahrweiler — Mon, 14 Sep 2026 20:20:04 +0000

Seal the Offer Before You Book### Preserve the details your booking decision is based on.

You find the perfect holiday apartment online.

The photos look great. The location is ideal. The listing promises air conditioning, a private parking space, sea views, free Wi-Fi, and flexible cancellation.

Those details make the difference, so you book the apartment and pay.

Several weeks later, you arrive.

There is no air conditioning. Parking costs extra. The promised sea view is blocked by another building.

You open the listing again, but some of the details have changed — or the original offer is no longer available.

Your booking confirmation shows the dates and the amount you paid. It may not contain every feature and promise that influenced your decision.

Now you wish you had preserved the complete offer before booking.

A screenshot is useful — but limited

You could take screenshots of every important webpage. That is better than having no record at all.

However, an ordinary screenshot can be edited. It does not provide an independent timestamp, and another person cannot easily determine whether it still contains the original pixels.

This is where Beaver Page Proof comes in.

Before booking, buying, travelling, or making another important decision, you open the offer in Beaver Page Proof and seal the webpage.

The app creates a proof package containing the captured page and the information required for later verification.

What the proof establishes

The sealed package preserves the webpage as it appeared when you created the proof.

Later verification can establish two important facts:

The sealed content existed by the confirmed timestamp.
The content inside the proof package has not been changed afterward. Even the smallest modification produces a different digital fingerprint and causes verification to fail.

The proof does not determine whether every statement on the webpage was true. It does not decide who is legally responsible or replace professional advice.

It preserves the information that was presented to you when you made your decision.

Verification is separate and free

A proof should not depend solely on the person who created it.

That is why Beaver Proof Verifier is a separate, free app. You can send the proof package to another person — a business, adviser, insurer, or lawyer — and they can verify it independently.

No Beaver account is required.

The timestamp is created through the open OpenTimestamps protocol and anchored to the Bitcoin blockchain. Beaver Proof does not upload the captured document or webpage to the blockchain. Only a cryptographic fingerprint becomes part of the timestamping process.

Your private content remains inside your proof package.

More than holiday bookings

The same principle applies whenever online information influences a later decision:

Product descriptions and condition statements
Used-item listings that disappear after a sale
Warranty and compatibility promises
Course contents and access commitments
Rental property descriptions
Service packages and advertised features
Competition rules and participation conditions
Public notices and published statements The right moment to preserve an offer is not after a disagreement begins.

It is before you rely on it.

Preserve first. Verify later.

Webpages are designed to change. Offers are updated, listings expire, and details can be removed.

Beaver Page Proof gives you a simple way to preserve the online information behind an important decision.

Before you book, buy, travel, or commit: seal the page.

Get Beaver Page Proof on the Mac App Store

Download Beaver Proof Verifier for free

Learn more at beaverproof.com.