CRC16 / CRC-A implementation of ISO 14443-3 in Java

main.java

// Eg run @ https://www.programiz.com/java-programming/online-compiler/
// data: 48 65 6C 6C 6F 20 57 6F 72 6C 64
// CRC-16: 52 7B


class Main {
    public static byte[] calculateCRC16(byte[] bytes) {
        byte chBlock;
        int wCRC = 0x6363;
        int i = 0;
        
        do {
            chBlock = bytes[i++];
            chBlock ^= (byte) (wCRC & 0x00FF);
            chBlock = (byte) (chBlock ^ (chBlock << 4));
            wCRC = ((wCRC >> 8) ^ ((chBlock & 0xFF) << 8) & 0xFFFF) ^
                   (((chBlock & 0xFF) << 3) & 0xFFFF) ^ 
                   (((chBlock & 0xFF) >> 4) & 0xFFFF);
        } while (i < bytes.length);
        
        return new byte[] { (byte) (wCRC & 0xFF), (byte) ((wCRC >> 8) & 0xFF) };
    }

    public static String bytesToHex(byte[] bytes) {
        StringBuilder result = new StringBuilder();
        for (byte b : bytes) {
            result.append(String.format("%02X ", b));
        }
        return result.toString().trim();
    }

    public static void main(String[] args) {
        byte[] data = "Hello World".getBytes();
        System.out.println("data: " + bytesToHex(data));
        byte[] crc = calculateCRC16(data);
        System.out.println("CRC-16: " + bytesToHex(crc));
    }
}