Example of RFID technology code related to Best RFID blocking cards

RFID Reader Basic Code Example (Using Java as an Example)
The following is a simplified Java code example for RFID reader initialization and tag reading, used to illustrate the basic process of RFID communication:

import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;
import java.io.InputStream;
import java.io.OutputStream;

public class RFIDReaderExample {
    public static void main(String[] args) {
        try {
            // 1. Initialize serial port communication
            CommPortIdentifier portIdentifier = CommPortIdentifier.getPortIdentifier("COM1");
            SerialPort serialPort = (SerialPort) portIdentifier.open("RFIDReader", 2000);
            serialPort.setSerialPortParams(9600, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);

            // 2. Get input and output streams
            InputStream inputStream = serialPort.getInputStream();
            OutputStream outputStream = serialPort.getOutputStream();

            // 3. Send read command (example command; adjust according to reader model)
            outputStream.write("AT+READTAG".getBytes());

            // 4. Read tag data
            byte[] buffer = new byte[64];
            int bytesRead = inputStream.read(buffer);
            String tagData = new String(buffer, 0, bytesRead).trim();

            // 5. Print tag data
            System.out.println("Tag Data: " + tagData);

            // 6. Close the connection
            serialPort.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

The technical principle and code association of RFID blocking card
The core technology of RFID blocking cards (such as VAULTRACARD, Credifence, etc.) is to prevent communication between readers and tags through electromagnetic interference. Its working principle can be analogized as:

Signal detection: Block the built-in circuit of the card to detect electromagnetic signals (such as 13.56MHz) emitted by the reader/writer.
Interference generation: Block the card from generating interference signals of the same frequency but opposite phase as the reader/writer signal, or reduce signal strength through energy absorption.
Communication interruption: The tag is unable to respond due to the inability to receive a valid signal, thereby preventing data reading.
Code level correlation: If simulating the blocking effect from the perspective of a reader/writer, interference logic can be inserted into the code (for principle explanation only, not actual blocking card implementation):

// Simulated RFID blocking card interference (pseudocode)
public class RFIDJammingExample {
    public static void main(String[] args) {
        // Assume the RFID reader is already initialized (same as the previous example)
        try {
            OutputStream outputStream = ...; // Get the output stream
            InputStream inputStream = ...;   // Get the input stream

            // 1. Send a read command to the RFID reader
            outputStream.write("AT+READTAG".getBytes());

            // 2. Simulate blocking: Continuously send interference signals (requires hardware support in reality)
            new Thread(() -> {
                try {
                    while (true) {
                        outputStream.write("JAMMING_SIGNAL".getBytes()); // Interference signal (placeholder)
                        Thread.sleep(10); // Control interference frequency (in milliseconds)
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }).start();

            // 3. Attempt to read the tag (should fail due to interference)
            byte[] buffer = new byte[64];
            int bytesRead = inputStream.read(buffer);
            if (bytesRead == -1) {
                System.out.println("Reading failed due to jamming.");
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Provide technical guidance on related content：
https://www.tjnfctag.com/best-rfid-blocking-cards/

Content source:
https://github.com/tianjunrfid-dotcom/generateRFIDonlinegenerator/releases/tag/RFIDblockingcards