Question

我正在用Java构建一个Blowfish密码算法。我使用these测试向量来查看它是否有效并且我发现最差可能的东西 - 它适用于某些输入而不适用于其他输入。

我使用Blowfish paper作为创建实现的指南。波纹管是它的相关部分。

public class Blowfish {
    // Binary Digits of Pi
    // ...
    private static final int N = 16;
    private final long S[][] = new long[4][256];
    private final long P[] = new long[N + 2];

密钥扩展

布鲁斯说：

（1）首先使用固定字符串依次初始化P阵列，然后按顺序初始化四个S盒。该字符串由pi的十六进制数字（少于初始3）

组成

 public void keyExpansion(String key) {
        System.arraycopy(p, 0, P, 0, N + 2);
        for (int i = 0; i < 4; i++) {
            System.arraycopy(s[i], 0, S[i], 0, 256);
        }

我意识到这不是真的可读，但小写p[]和s[][]包含固定值（pi的十六进制数字），大写P[]和S[][]是a的属性Blowfish对象，将会发生变化。

布鲁斯说：

（2）XOR P1与密钥的前32位，XOR P2与密钥的第二个32位，依此类推，用于密钥的所有位（可能高达P14）。重复循环通过密钥位，直到整个P阵列与密钥位进行异或。

for (int i = 0; i < N + 2; i++) {
    int begin = (i * 8) % key.length();
    int end = ((i + 1) * 8) % key.length();
    String keySubstring;
    if (begin < end) {
        keySubstring = key.substring(begin, end);
    } else {
        keySubstring = key.substring(begin) + key.substring(0, end);
    }
    long keyChunk = Long.parseLong(keySubstring, 16);
    P[i] ^= keyChunk;
}

由于密钥长度不变（最多56个字节），因此我认为最简单的方法是传递它是一个字符串。也许我应该使用BigInteger？

布鲁斯说：

（3）使用Blowfish算法加密全零字符串步骤（1）和（2）中描述的子键。

（4）用步骤（3）的输出替换P1和P2。

（5）使用Blowfish算法加密步骤（3）的输出修改过的子项。

（6）用步骤（5）的输出替换P3和P4。

（7）继续该过程，替换P阵列的所有条目，和然后按顺序排列所有四个S盒，输出不断变化的Blowfish算法。

long e = 0;
for (int i = 0; i < N + 2; i += 2) {
    e = encrypt(e);
    long eL = trim(e >>> 32);
    long eR = trim(e);
    P[i] = eL;
    P[i + 1] = eR;
}

for (int i = 0; i < 4; i++) {
    for (int j = 0; j < 256; j += 2) {
        e = encrypt(e);
        long eL = trim(e >>> 32);
        long eR = trim(e);
        S[i][j] = eL;
        S[i][j + 1] = eR;
    }
}

这是一个很好的时间，任何提及我的帮助函数trim删除更高的32位。

private static long trim(long value) {
    return value & 0xFFFFFFFFL;
}

加密

布鲁斯说：

Blowfish是一个由16轮组成的Feistel网络。输入是64位数据元素x。

将x分为两个32位：xL，xR

对于i = 1到16：

xL = xL XOR Pi

xR = F（xL）XOR xR

交换xL和xR

下一个

交换xL和xR（撤消最后一次交换。）

xR = xR XOR P17

xL = xL XOR P18

重组xL和xR

public long encrypt(long plaintext) {
        long xL = trim(plaintext >>> 32);
        long xR = trim(plaintext);

        for (int i = 0; i < N; i++) {
            xL = xL ^ P[i];
            xR = F(xL) ^ xR;
            //swap
            xL = xL + xR;
            xR = xL - xR;
            xL = xL - xR;
        }
        //swap
        xL = xL + xR;
        xR = xL - xR;
        xL = xL - xR;

        //final step
        xR = xR ^ P[N];
        xL = xL ^ P[N + 1];

        return (xL << 32) | xR;
    }
}

测试

我只是针对上述测试向量运行此代码，如下所示：

  public void testBlowfish() {
        long key[] = {
            ...
        };
        long clear[] = {
            ...
        };
        long cipher[] = {
            ...
        };
        Blowfish b = new Blowfish();
        for (int i = 0; i < 34; i++) {
            b.keyExpansion(Long.toHexString(key[i]));
            long result = b.encrypt(clear[i]);
            if (result == cipher[i]) {
                System.out.println("Test " + i + " passed!");
            } else {
                System.out.println("Test " + i + " failed: ");
                System.out.println("\tKey:\t" + Long.toHexString(key[i]));
                System.out.println("\tClear:\t" + Long.toHexString(clear[i]));
                System.out.println("\tCipher:\t" + Long.toHexString(cipher[i]));
                System.out.println("\tResult:\t" + Long.toHexString(result));
            }
        }
    }

以下是测试结果：

Test 0 passed!
Test 1 passed!
Test 2 passed!
Test 3 passed!
Test 4 failed: 
    Key:    123456789abcdef
    Clear:  1111111111111111
    Cipher: 61f9c3802281b096
    Result: 65a2dfe88702a6bf
Test 5 passed!
Test 6 passed!
Test 7 passed!
Test 8 passed!
Test 9 failed: 
    Key:    131d9619dc1376e
    Clear:  5cd54ca83def57da
    Cipher: b1b8cc0b250f09a0
    Result: fbd7e706e563d21a
Test 10 failed: 
    Key:    7a1133e4a0b2686
    Clear:  248d43806f67172
    Cipher: 1730e5778bea1da4
    Result: 7d11a2563bbf76f1
Test 11 passed!
Test 12 failed: 
    Key:    4b915ba43feb5b6
    Clear:  42fd443059577fa2
    Cipher: 353882b109ce8f1a
    Result: d747d42ef2bc89c0
Test 13 failed: 
    Key:    113b970fd34f2ce
    Clear:  59b5e0851cf143a
    Cipher: 48f4d0884c379918
    Result: c559acf605825008
Test 14 failed: 
    Key:    170f175468fb5e6
    Clear:  756d8e0774761d2
    Cipher: 432193b78951fc98
    Result: 8761d08e81a796d
Test 15 passed!
Test 16 failed: 
    Key:    7a7137045da2a16
    Clear:  3bdd119049372802
    Cipher: 2eedda93ffd39c79
    Result: db47a054a5a0d496
Test 17 failed: 
    Key:    4689104c2fd3b2f
    Clear:  26955f6835af609a
    Cipher: d887e0393c2da6e3
    Result: 40f96e5f9f3affe1
Test 18 passed!
Test 19 passed!
Test 20 passed!
Test 21 failed: 
    Key:    25816164629b007
    Clear:  480d39006ee762f2
    Cipher: 7555ae39f59b87bd
    Result: a6cb030922383650
Test 22 passed!
Test 23 passed!
Test 24 passed!
Test 25 failed: 
    Key:    18310dc409b26d6
    Clear:  1d9d5c5018f728c2
    Cipher: d1abb290658bc778
    Result: d45634df2f8eb002
Test 26 passed!
Test 27 failed: 
    Key:    101010101010101
    Clear:  123456789abcdef
    Cipher: fa34ec4847b268b2
    Result: 30ce63f436ff5475
Test 28 passed!
Test 29 passed!
Test 30 passed!
Test 31 passed!
Test 32 failed: 
    Key:    123456789abcdef
    Clear:  0
    Cipher: 245946885754369a
    Result: 291c4bd096af70e5
Test 33 passed!

正如我所说，一些投入有效，有些则没有。我无法弄清楚为什么，这对我来说似乎是随意的，我拒绝生活在计算机可以做出任意决定的世界里。换句话说，错误在哪里？

Answer 1

As suggested, I was losing leading zeros in conversions. Implementation was fine, but in test the line

b.keyExpansion(Long.toHexString(key[i]));

was causing errors. Replacing it with

b.keyExpansion(String.format("%016x", key[i]));

worked.

Seems obvious now, since each failed test at least one had leading zero.

Edit

I assumed that every key will be longer than 8 bytes, for some reason. To get keyExpansion to work for short keys, I changed reading from key like so:

for (int i = 0; i < N + 2; i++) {
    StringBuilder keySubstring = new StringBuilder();
    for (int j = 0; j < 8; j++) {
        int index = (i * 8 + j) % key.length();
        keySubstring.append(key.charAt(index));
    }
    long keyChunk = Long.parseLong(keySubstring.toString(), 16);
    P[i] ^= keyChunk;
}

Java中的Blowfish实现

密钥扩展

加密

测试

1 个答案:

Edit