A5Cipher.java

package com.thealgorithms.ciphers.a5;

import java.util.BitSet;

// https://en.wikipedia.org/wiki/A5/1
public class A5Cipher {
    private final A5KeyStreamGenerator keyStreamGenerator;
    private static final int KEY_STREAM_LENGTH = 228; // 28.5 bytes so we need to pad bytes or something

    public A5Cipher( BitSet sessionKey, BitSet frameCounter ) {
        keyStreamGenerator = new A5KeyStreamGenerator();
        keyStreamGenerator.initialize( sessionKey, frameCounter );
    }

    public BitSet encrypt( BitSet plainTextBits ) {
        // create a copy
        var result = new BitSet( KEY_STREAM_LENGTH );
        result.xor( plainTextBits );

        var key = keyStreamGenerator.getNextKeyStream();
        result.xor( key );

        return result;
    }

    public void resetCounter() {
        keyStreamGenerator.reInitialize();
    }

}