java实现rc4算法代码

以下是Java实现RC4算法的代码：

public class RC4 {
    private int[] S = new int[256];
    private int[] T = new int[256];
    private int keylen;

    public RC4(byte[] key) {
        keylen = key.length;
        for (int i = 0; i < 256; i++) {
            S[i] = i;
            T[i] = key[i % keylen];
        }
        int j = 0;
        for (int i = 0; i < 256; i++) {
            j = (j + S[i] + T[i]) % 256;
            int tmp = S[i];
            S[i] = S[j];
            S[j] = tmp;
        }
    }

    public byte[] encrypt(byte[] plaintext) {
        byte[] ciphertext = new byte[plaintext.length];
        int i = 0, j = 0;
        for (int n = 0; n < plaintext.length; n++) {
            i = (i + 1) % 256;
            j = (j + S[i]) % 256;
            int tmp = S[i];
            S[i] = S[j];
            S[j] = tmp;
            int k = S[(S[i] + S[j]) % 256];
            ciphertext[n] = (byte) (plaintext[n] ^ k);
        }
        return ciphertext;
    }

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

使用示例：

byte[] key = "secretkey".getBytes();
byte[] data = "Hello, world!".getBytes();
RC4 rc4 = new RC4(key);
byte[] encrypted = rc4.encrypt(data);
byte[] decrypted = rc4.decrypt(encrypted);
System.out.println(new String(data)); // Hello, world!
System.out.println(new String(encrypted)); // †VÙ"áÝ*š
System.out.println(new String(decrypted)); // Hello, world!