Difference Between Quantum and Post-Quantum Encryption: Why It Matters for Blockchain

#postquantum #cryptography #blockchain #encryption

Everyone says: "Quantum technologies are the future".

But few understand the difference between quantum encryption and post-quantum cryptography.

Let's start with the first.

Quantum encryption sounds futuristic — and indeed it's cool: photons, superposition, quantum entanglement...

This is physics at the particle level. Almost magic. But there's a nuance: all this only works with expensive specialized equipment. And in practice, it is almost never used — too complicated, too early.

But post-quantum cryptography is already a reality.

It does not require quantum devices and does not use quantum effects.

The task of post-quantum cryptography is to protect us from the threats that quantum computers will bring when they break familiar algorithms like RSA.

And here a serious problem emerges: most blockchains — from Bitcoin to Ethereum — were not initially designed for cryptography replacement. Adding post-quantum protection to them is almost impossible.

In Cellframe, we foresaw this in advance. Our architecture supports post-quantum algorithms from the very beginning. And most importantly — it allows them to be easily changed when necessary.

If an algorithm becomes outdated or is compromised — it can be disabled and replaced.

Today, Cellframe already supports CRYSTALS-Dilithium and Falcon — algorithms recommended by world experts and undergoing standardization at the NIST level.

When quantum computers become reality, Cellframe won't be playing catch-up — it will meet the threat fully armed.

Glossary of Quantum and Post-Quantum Terms

Quantum Encryption

A cryptographic method that uses quantum physics principles (photons, superposition, quantum entanglement) to secure data. Requires expensive specialized equipment and is not yet practically applicable at scale.

Post-Quantum Cryptography

Cryptographic algorithms designed to protect against attacks from future quantum computers. Does not require quantum devices and is implementable on classical computers. Its purpose is to secure systems before quantum threats materialize.

Quantum Computer

A future computing device that uses quantum bits (qubits) to perform calculations exponentially faster than classical computers. Will be capable of breaking current cryptographic algorithms like RSA, ECDSA, and others.

RSA (Algorithm)

A widely used public-key cryptographic algorithm that will be vulnerable to attacks by sufficiently powerful quantum computers using Shor's algorithm.

Cryptography

The science of securing information through mathematical algorithms. In blockchain, it ensures transaction integrity, wallet security, and network consensus.

Superposition

A quantum physics principle where a particle can exist in multiple states simultaneously. Used in quantum encryption but not in post-quantum cryptography.

Quantum Entanglement

A quantum phenomenon where particles remain connected such that the state of one instantly affects the other, regardless of distance. Applied in quantum encryption, not in post-quantum algorithms.

CRYSTALS-Dilithium

A post-quantum digital signature algorithm recommended by NIST, based on lattice-based cryptography. Used in Cellframe for quantum-resistant security.

NIST (National Institute of Standards and Technology)

The US federal agency that develops technology and cybersecurity standards. NIST is currently standardizing post-quantum cryptographic algorithms to prepare for the quantum era.

FAQ: Post-Quantum Cryptography

What is quantum encryption and how is it different from post-quantum cryptography?

Quantum encryption uses quantum physics (photons, entanglement) and requires quantum devices. Post-quantum cryptography uses classical computers with new mathematical algorithms designed to resist quantum attacks. They are fundamentally different: one needs quantum hardware, the other doesn't.

Why isn't quantum encryption used in practice?

Quantum encryption requires extremely expensive, specialized equipment. It is still in experimental stages, complex to implement, and not scalable for mass adoption. The technology is "too early" for practical blockchain applications.

Why do we need post-quantum cryptography if quantum computers don't exist yet?

Quantum computers are actively being developed by companies like IBM, Google, and governments. When they arrive, they will instantly break RSA and other current algorithms. We must prepare now — upgrading cryptographic infrastructure takes years, and any data encrypted today can be stored and decrypted later ("harvest now, decrypt later" attack).

Why can't Bitcoin and Ethereum easily add post-quantum protection?

These blockchains were built with fixed cryptographic algorithms deeply integrated into their consensus, transaction formats, and wallet systems. Replacing them would require a hard fork affecting every user, node, and application — a massive, risky undertaking. Their architecture wasn't designed for cryptographic agility.