DES蛮力(学术) [英] DES Brute Force (academic)
问题描述
我正在上一门计算机安全课程，我们的任务之一是暴力破解具有弱密钥的DES.
I am taking a class in computer security, one of our assignments is to brute force DES that has a weak key.
我的代码:
public static void main(String[] args) throws Exception {
String temp;
String current;
String plaintext;
//Generate key for DES
String initkey = "00000006";
byte[] Rawkey = initkey.getBytes();
DESKeySpec dks = new DESKeySpec(Rawkey);
SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
SecretKey desKey = skf.generateSecret(dks);
//Text Enc & Dec
Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
//Declare wether to enc or dec
cipher.init(Cipher.ENCRYPT_MODE,desKey);
byte []message = "Decrypted Successfully".getBytes();
byte []messageEnc = cipher.doFinal(message);
plaintext = new String(message);
System.out.println("Cipher Text: " + new String(messageEnc) );
for(int i=0;i<10;i++){
try{
temp = padLeftZeros(Integer.toString(i),8);
System.out.println(temp);
byte []RawkeyTest = temp.getBytes();
DESKeySpec dksTest = new DESKeySpec(RawkeyTest);
SecretKeyFactory skf2 = SecretKeyFactory.getInstance("DES");
SecretKey desKeyTest = skf2.generateSecret(dksTest);
cipher.init(Cipher.DECRYPT_MODE,desKeyTest);
byte []dec = cipher.doFinal(messageEnc);
current = new String(dec);
if(current.equals(plaintext)){
System.out.println("Decrypted Text: " + current);
System.out.println("");
//break;
}
}catch (BadPaddingException ex){
System.out.println("Wrong Key.");
System.out.println("");
}
}
}
public static String padLeftZeros(String inputString, int length) {
if (inputString.length() >= length) {
return inputString;
}
StringBuilder sb = new StringBuilder();
while (sb.length() < length - inputString.length()) {
sb.append('0');
}
sb.append(inputString);
return sb.toString();
}
}
输出
Cipher Text: �
B��4#Ǡ�`=Π��H�č:�
00000000
Wrong Key.
00000001
Wrong Key.
00000002
Wrong Key.
00000003
Wrong Key.
00000004
Wrong Key.
00000005
Wrong Key.
00000006
Decrypted Text: Decrypted Successfully
00000007
Decrypted Text: Decrypted Successfully
00000008
Wrong Key.
00000009
Wrong Key.
00000010
Wrong Key.
00000011
Wrong Key.
00000012
Wrong Key.
00000013
Wrong Key.
00000014
Wrong Key.
00000015
Wrong Key.
00000016
Decrypted Text: Decrypted Successfully
00000017
Decrypted Text: Decrypted Successfully
00000018
Wrong Key.
00000019
Wrong Key.
密钥#6是唯一应该成功解密的密钥.所以我不明白为什么键7、16、17也能正常工作.
The key #6 is the only one that is supposed to decrypt successfully. So I don't understand why the keys: 7, 16, 17 works as well.
任何帮助或建议将不胜感激.预先感谢.
Any help or advice would be greatly appreciated. Thanks in advance.
推荐答案
没有问题，实际上有一个问题.
There is no problem, actually, there is one.
DES通常使用64位密钥，其中每个字节的最后一位(lsb)是奇偶校验位，因此总共有56位加密密钥.奇偶校验位对密钥调度没有帮助.这就是为什么我们说DES具有56位密钥大小的原因.一旦检查了奇偶校验，它们将被丢弃.密钥的每个字节必须具有奇数奇偶校验.该库忽略奇偶校验问题，并且不提供异常.
DES normally uses 64-bit keys where the last bit (lsb) of each byte is a parity bit and that makes a total of 56 bits of cryptographic keys. The parity bits don't contribute to the key schedule. This is why we say DES has a 56-bit key size. They are discarded once the parity is checked. Each byte of the key must have odd parity. The library ignores the parity problem and doesn't provide an exception.
-
0x0 ... 6 = 0x..0110和7 = 0x..0111.如果删除正确的位，则它们是相同的.
0x0...6 = 0x..0110and7=0x..0111. If you remove the right bit they are the same.
0x0..16 = 0x ... 0001 0110 和 17 = 0x ... 0001 0111 .现在删除每个字节的最后一位，然后密钥将与 0x00000006
0x0..16 = 0x...0001 0110 and 17=0x...0001 0111. Now remove the last bits in each of the bytes, then the keys will be the same as 0x00000006
并且请注意，上述所有密钥都不对奇偶校验有效.如果要检查奇偶校验或使密钥有效，则可以使用 Alejandro Revilla github
And note that none of the above keys are valid in terms of parity. If you want to check the parity or make your keys valid you can use the following Java code from Alejandro Revilla github
public static void adjustDESParity (byte[] bytes) {
for (int i = 0; i < bytes.length; i++) {
int b = bytes[i];
bytes[i] = (byte)((b & 0xfe) | ((((b >> 1) ^ (b >> 2) ^ (b >> 3) ^ (b >> 4) ^ (b >> 5) ^ (b >> 6) ^ (b >> 7)) ^ 0x01) & 0x01));
}
}
public static boolean isDESParityAdjusted (byte[] bytes) {
byte[] correct = (byte[])bytes.clone();
adjustDESParity(correct);
return Arrays.equals(bytes, correct);
}
如果您正在寻找DES的弱键，那是
If you are looking for the DES's weak keys then those are
0101 0101 0101 0101
1F1F 1F1F 0E0E 0E0E
E0E0 E0E0 F1F1 F1F1
FEFE FEFE FEFE FEFE
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