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我目前在做Sipdroid的加解密,现在我已经成功进行了加密操作,经过测试可以达到加密效果。但是我在几个地方都尝试了解密,要么通讯双方没有声音,要么通讯双方有嘈杂的噪音。 我想就如何解密这个东西寻求帮助。 首先,我为 RC4 加密编写了一个名为 RC4encrypt.class 的类:

public class RC4encrypt {
public static byte[] encryptWithRC4(byte[] content, String key) throws Exception {
    SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
    secureRandom.setSeed(key.getBytes());
    KeyGenerator keyGenerator = KeyGenerator.getInstance("RC4");
    keyGenerator.init(secureRandom);
    SecretKey secretKey = keyGenerator.generateKey();

    Cipher cipher = Cipher.getInstance("RC4");
    cipher.init(Cipher.ENCRYPT_MODE, secretKey);

    return cipher.doFinal(content);
}

public static byte[] decryptWithRC4(byte[] cipherText, String key) throws Exception {
    SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
    secureRandom.setSeed(key.getBytes());
    KeyGenerator keyGenerator = KeyGenerator.getInstance("RC4");
    keyGenerator.init(secureRandom);
    SecretKey secretKey = keyGenerator.generateKey();

    Cipher cipher = Cipher.getInstance("RC4");
    cipher.init(Cipher.DECRYPT_MODE, secretKey);

    return cipher.doFinal(cipherText);
}

}

然后我给 RtpSocket.class 写了一个函数 send_Encrypt:

private byte[] send_Encrypt(byte[] data ,int header_len){
    byte [] header_byte = new byte[data.length];
    byte [] body_byte = new byte[data.length - header_len];
    for(int i = 0 ;i<header_len-1;i++){
        header_byte[i] = data[i];
    }
    for(int i =0  ;i<(data.length - header_len)-1;i++){
        body_byte[i] = data[header_len+i];
    }
    try {
        body_byte = RC4encrypt.encryptWithRC4(body_byte,"gfhfdhgdfgh");
    } catch (Exception e) {
        e.printStackTrace();
    }
    for(int i = 0 ;i<body_byte.length-1;i++){
        header_byte[header_len+i] = body_byte[i];
    }
    return  header_byte;
}

之后我对 RtpSocket.class 中的 send 函数做了一些修改:

public void send(RtpPacket rtpp) throws IOException {
    byte[] data = rtpp.packet;
    int len = rtpp.getHeaderLength();
    data = send_Encrypt(data,len);
    datagram.setData(data);
    datagram.setLength(rtpp.packet.length);
    datagram.setAddress(r_addr);
    datagram.setPort(r_port);
    socket.send(datagram);
}

我用修改后的程序和原程序通话,一侧声音是噪音,另一侧可以听到正常通话,说明加密成功,但是我用同样的方法修改receive功能时就可以了无法实现。那么有人可以指导我吗?

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