Salsa20实现java

Salsa20是一种流加密算法，可以用于保护数据的机密性。以下是一个Salsa20的Java实现：

public class Salsa20 {

    private int[] state = new int[16];

    public Salsa20(byte[] key, byte[] iv) {
        int[] constants = {0x61707865, 0x3320646e, 0x79622d32, 0x6b206574};
        int[] keyWords = new int[key.length / 4];
        int[] ivWords = new int[iv.length / 4];
        ByteBuffer.wrap(key).order(ByteOrder.LITTLE_ENDIAN).asIntBuffer().get(keyWords);
        ByteBuffer.wrap(iv).order(ByteOrder.LITTLE_ENDIAN).asIntBuffer().get(ivWords);
        int[] sigma = {0x61707865, 0x3120646e, 0x79622d36, 0x6b206574};
        state[0] = constants[0];
        state[1] = keyWords[0];
        state[2] = keyWords[1];
        state[3] = keyWords[2];
        state[4] = keyWords[3];
        state[5] = constants[1];
        state[6] = ivWords[0];
        state[7] = ivWords[1];
        state[8] = constants[2];
        state[9] = keyWords[4];
        state[10] = keyWords[5];
        state[11] = keyWords[6];
        state[12] = keyWords[7];
        state[13] = constants[3];
        state[14] = ivWords[2];
        state[15] = ivWords[3];
        int[] temp = new int[16];
        for (int i = 0; i < 16; i++) {
            temp[i] = state[i];
        }
        for (int i = 0; i < 10; i++) {
            quarterRound(temp, 0, 4, 8, 12);
            quarterRound(temp, 1, 5, 9, 13);
            quarterRound(temp, 2, 6, 10, 14);
            quarterRound(temp, 3, 7, 11, 15);
            quarterRound(temp, 0, 5, 10, 15);
            quarterRound(temp, 1, 6, 11, 12);
            quarterRound(temp, 2, 7, 8, 13);
            quarterRound(temp, 3, 4, 9, 14);
        }
        for (int i = 0; i < 16; i++) {
            state[i] += temp[i];
        }
    }

    private void quarterRound(int[] x, int a, int b, int c, int d) {
        x[b] ^= Integer.rotateLeft(x[a] + x[d], 7);
        x[c] ^= Integer.rotateLeft(x[b] + x[a], 9);
        x[d] ^= Integer.rotateLeft(x[c] + x[b], 13);
        x[a] ^= Integer.rotateLeft(x[d] + x[c], 18);
    }

    public byte[] encrypt(byte[] input) {
        int[] output = new int[input.length / 4];
        ByteBuffer.wrap(input).order(ByteOrder.LITTLE_ENDIAN).asIntBuffer().get(output);
        for (int i = 0; i < output.length; i += 16) {
            int[] block = new int[16];
            for (int j = 0; j < 16; j++) {
                block[j] = output[i + j];
            }
            int[] temp = new int[16];
            for (int j = 0; j < 16; j++) {
                temp[j] = state[j];
            }
            for (int j = 0; j < 10; j++) {
                quarterRound(temp, 0, 4, 8, 12);
                quarterRound(temp, 1, 5, 9, 13);
                quarterRound(temp, 2, 6, 10, 14);
                quarterRound(temp, 3, 7, 11, 15);
                quarterRound(temp, 0, 5, 10, 15);
                quarterRound(temp, 1, 6, 11, 12);
                quarterRound(temp, 2, 7, 8, 13);
                quarterRound(temp, 3, 4, 9, 14);
            }
            for (int j = 0; j < 16; j++) {
                block[j] += temp[j];
            }
            for (int j = 0; j < 16; j++) {
                output[i + j] = block[j];
            }
            state[8]++;
            if (state[8] == 0) {
                state[9]++;
            }
        }
        ByteBuffer buffer = ByteBuffer.allocate(input.length);
        for (int i = 0; i < output.length; i++) {
            buffer.putInt(output[i]);
        }
        return buffer.array();
    }

    public byte[] decrypt(byte[] input) {
        return encrypt(input);
    }

}

该实现使用Little Endian字节序和32位整数。使用给定的密钥和IV创建Salsa20对象，然后可以使用`encrypt()`方法加密数据，使用`decrypt()`方法解密数据。