RC4加密java [英] RC4 encryption java
本文介绍了RC4加密java的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
public class RC4 {
private int [] S = new int [256];
private int [] T = new int [256];
private int keylen;
public RC4（byte [] key）throws异常{
if（key.length< 1 || key.length> 256）{
throw new Exception（密钥必须在1到256字节之间）;
} else {
keylen = key.length; （int i = 0; i <256; i ++）{
S [i] = i;
T [i] = key [i％keylen];
}
int j = 0; （int i = 0; i< 256; i ++）{
j =（j + S [i] + T [i]）％256;
S [i] ^ = S [j];
S [j] ^ = S [i];
S [i] ^ = S [j];
}
}
}
public int [] encrypt（int [] plaintext）{
int [] ciphertext = new int [plaintext.length ]。
int i = 0，j = 0，k，t; （int counter = 0; counter< plaintext.length; counter ++）{
i =（i + 1）％256;
j =（j + S [i]）％256;
S [i] ^ = S [j];
S [j] ^ = S [i];
S [i] ^ = S [j];
t =（S [i] + S [j]）％256;
k = S [t];
ciphertext [counter] = plaintext [counter] ^ k;
}
返回密文;
}
public int [] decrypt（int [] ciphertext）{
return encrypt（ciphertext）;
}
}
我有几个问题：
-
为什么上述代码中的纯文本是
int数组？ -
当我测试这个代码时，我得到了奇怪的结果，有人可以向我解释吗？这里我的代码测试：
public class RC4_Main {
public static void main（String args [ ]）throws Exception {
String keyword =hello;
byte [] keytest = keyword.getBytes（）; //将关键字转换为字节
int [] text = {1，2，3，4，5}; // text as 12345
RC4 rc4 = new RC4（keytest）;
System.out.print（\\\
original text：）; （int i = 0; i< text.length; i ++）{
System.out.print（text [i]）;
}
int [] cipher = rc4.encrypt（text）; // encryption
System.out.print（\\\
cipher：）; （int i = 0; i< cipher.length; i ++）{
System.out.print（cipher [i]）;
}
int [] backtext = rc4.decrypt（cipher）; // decrypt
System.out.print（\\\
back to text：）; （int i = 0; i< backtext.length; i ++）{
System.out.print（backtext [i]）;
}
System.out.println（）;
}
}
这是结果：（原始和回到文本不是SAME）为什么???
原文：12345
密码：1483188254174
返回文本：391501310217
解决方案
有一些事情需要注意：
- 当您需要无符号字节（例如索引）时，Java不是很容易使用;
- 如果您在
S和T中创建状态，您应该真的注意到这些值改变，当你使用相同的实例解密 时，你采用加密的状态; - 上面的代码不是非常有效的内存明智，您可以轻松地重写它来采取字节数组;
- 使用一个String，在将参数重构为
byte []之后首先需要使用字符编码，首先，例如使用String.getBytes（Charset charset）;
更容易，并且有一些有趣的深夜黑客攻击，我改进了您的代码，并针对 rfc6229 使用零字节数组。
更新：由于micahk指出以下，使用的恶性C XOR交换阻止了此代码加密最终Java中的输入字节。使用常规的旧交换修复它。
警告：以下代码应被视为编码练习。请使用一个经过验证的库，而不是下面的代码片段在您的应用程序中执行RC4（或Ron的代码4，ARC4等）。这意味着使用 Cipher.getInstance（RC4）; 或Bouncy Castle的ARC4类。
public class RC4 {
private final byte [] S = new byte [256];
private final byte [] T = new byte [256];
private final int keylen;
public RC4（final byte [] key）{
if（key.length< 1 || key.length> 256）{
throw new IllegalArgumentException（
键必须在1到256字节之间）;
} else {
keylen = key.length; （int i = 0; i <256; i ++）{
S [i] =（byte）i;
T [i] = key [i％keylen];
}
int j = 0;
byte tmp; （int i = 0; i <256; i ++）{
j =（j + S [i] + T [i]）& 0xFF的;
tmp = S [j];
S [j] = S [i];
S [i] = tmp;
}
}
}
public byte [] encrypt（final byte [] plaintext）{
final byte [] ciphertext = new byte [plaintext 。长度];
int i = 0，j = 0，k，t;
byte tmp; （int counter = 0; counter< plaintext.length; counter ++）{
i =（i + 1）& 0xFF的;
j =（j + S [i]）& 0xFF的;
tmp = S [j];
S [j] = S [i];
S [i] = tmp;
t =（S [i] + S [j]）& 0xFF的;
k = S [t];
ciphertext [counter] =（byte）（plaintext [counter] ^ k）;
}
返回密文;
}
public byte [] decrypt（final byte [] ciphertext）{
return encrypt（ciphertext）;
}
}
快乐编码
Hi there I am trying to implement the RC4 algorithm in Java. I found this code as an example that help me to understand the idea:
public class RC4 {
private int[] S = new int[256];
private int[] T = new int[256];
private int keylen;
public RC4(byte[] key) throws Exception {
if (key.length < 1 || key.length > 256) {
throw new Exception("key must be between 1 and 256 bytes");
} else {
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;
S[i] ^= S[j];
S[j] ^= S[i];
S[i] ^= S[j];
}
}
}
public int[] encrypt(int[] plaintext) {
int[] ciphertext = new int[plaintext.length];
int i = 0, j = 0, k, t;
for (int counter = 0; counter < plaintext.length; counter++) {
i = (i + 1) % 256;
j = (j + S[i]) % 256;
S[i] ^= S[j];
S[j] ^= S[i];
S[i] ^= S[j];
t = (S[i] + S[j]) % 256;
k = S[t];
ciphertext[counter] = plaintext[counter] ^ k;
}
return ciphertext;
}
public int[] decrypt(int[] ciphertext) {
return encrypt(ciphertext);
}
}
I have few question:
Why is the plain-text an
intarray in the above code?When I test this code I get strange result, can somebody explain to me? Here my code to test:
public class RC4_Main { public static void main(String args[]) throws Exception { String keyword = "hello"; byte[] keytest = keyword.getBytes(); //convert keyword to byte int[] text = {1, 2, 3, 4, 5}; // text as 12345 RC4 rc4 = new RC4(keytest); System.out.print("\noriginal text: "); for (int i = 0; i < text.length; i++) { System.out.print(text[i]); } int[] cipher = rc4.encrypt(text); //encryption System.out.print("\ncipher: "); for (int i = 0; i < cipher.length; i++) { System.out.print(cipher[i]); } int[] backtext = rc4.decrypt(cipher); //decryption System.out.print("\nback to text: "); for (int i = 0; i < backtext.length; i++) { System.out.print(backtext[i]); } System.out.println(); } }
Here is the result: (original and back to text are not SAME) why???
original text: 12345
cipher: 1483188254174
back to text: 391501310217
解决方案
There are a few things to notice:
- Java is not very easy to use when you require unsigned bytes (e.g. for indexing);
- if you create a state in
SandT, you should really notice that these values change, when you decrypt with the same instance you take the state used for encryption; - the above code is not very efficient memory wise, and you can easily rewrite it to take byte arrays;
- to use a String, after refactoring the arguments to
byte[], you first need to use character-encoding first, e.g. usingString.getBytes(Charset charset);
To make life easier, and to have some fun late night hacking, I improved your code and tested it against a single vector in rfc6229 using a zero'd out byte array.
UPDATE: As micahk points out below, the evil C XOR swap that was used prevented this code from encrypting the final byte of input in Java. Using regular old swaps fixes it.
Warning: the code below should be considered a coding exercise. Please use a well vetted library instead of the code snippet below to perform RC4 (or Ron's Code 4, ARC4 etc.) in your application. That means using Cipher.getInstance("RC4"); or the ARC4 classes in Bouncy Castle.
public class RC4 {
private final byte[] S = new byte[256];
private final byte[] T = new byte[256];
private final int keylen;
public RC4(final byte[] key) {
if (key.length < 1 || key.length > 256) {
throw new IllegalArgumentException(
"key must be between 1 and 256 bytes");
} else {
keylen = key.length;
for (int i = 0; i < 256; i++) {
S[i] = (byte) i;
T[i] = key[i % keylen];
}
int j = 0;
byte tmp;
for (int i = 0; i < 256; i++) {
j = (j + S[i] + T[i]) & 0xFF;
tmp = S[j];
S[j] = S[i];
S[i] = tmp;
}
}
}
public byte[] encrypt(final byte[] plaintext) {
final byte[] ciphertext = new byte[plaintext.length];
int i = 0, j = 0, k, t;
byte tmp;
for (int counter = 0; counter < plaintext.length; counter++) {
i = (i + 1) & 0xFF;
j = (j + S[i]) & 0xFF;
tmp = S[j];
S[j] = S[i];
S[i] = tmp;
t = (S[i] + S[j]) & 0xFF;
k = S[t];
ciphertext[counter] = (byte) (plaintext[counter] ^ k);
}
return ciphertext;
}
public byte[] decrypt(final byte[] ciphertext) {
return encrypt(ciphertext);
}
}
Happy coding.
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