我试图通过添加解密模块来扩展Speck密码(https://github.com/inmcm/Simon_Speck_Ciphers)的以下实现。我按照NSA关于Speck和Simon的原始文件(https://eprint.iacr.org/2013/404)中的说明实现了解密算法。
现在我有点困了,因为我无法正确破译加密程序生成的密码文本。我已经看了其他类似的问题张贴在这里,所以没有效果。
通过检查我的代码和stdout,我注意到在解密阶段存储在x_word中的值是不正确的,从第一次迭代开始。因此,以下指令可能存在问题:

x_word = rotate_left( (sub_mod((x_word ^ *(round_key_ptr + 21 - i)), y_word, 65535)), 7);

我在这里发布我的代码的相关部分:
#define rotate_left(x,n) (x >> (word_size - n)) | (x << n)
#define rotate_right(x,n) (x << (word_size - n)) | (x >> n)

void Speck_Encrypt_32(uint8_t *key_schedule, uint8_t *plaintext, uint8_t *ciphertext) {

    const uint8_t word_size = 16;
    uint16_t y_word = *(uint16_t *)plaintext;
    uint16_t x_word = *(((uint16_t *)plaintext) + 1);
    uint16_t *round_key_ptr = (uint16_t *)key_schedule;
    uint16_t * word_ptr = (uint16_t *)ciphertext;

    for(uint8_t i = 0; i < 22; i++) {  // Block size 32 has only one round number option

        x_word = ((rotate_right(x_word, 7)) + y_word) ^ *(round_key_ptr + i);
        y_word = (rotate_left(y_word, 2)) ^ x_word;

        printf("y_word - (%d) - %u\n", i, (unsigned int)y_word);
        printf("x_word - (%d) - %u\n", i, (unsigned int)x_word);
    }
    // Assemble Ciphertext Output Array
    *word_ptr = y_word;
    word_ptr += 1;
    *word_ptr = x_word;
    return;
}

static inline uint16_t sub_mod(uint16_t a, uint16_t b, uint16_t m)
{
  if ( a>=b )
    return a - b;
  else
    return m - b + a;
}


void Speck_Decrypt_32(uint8_t *key_schedule, uint8_t *plaintext, uint8_t *ciphertext) {

    const uint8_t word_size = 16;
    // Swapping cipher text words
    uint16_t y_word = *(uint16_t *)ciphertext;
    uint16_t x_word = *(((uint16_t *)ciphertext) + 1);
    uint16_t *round_key_ptr = (uint16_t *)key_schedule;
    uint16_t * word_ptr = (uint16_t *)plaintext;

    for(int i=0; i < 4; i++) {
        printf("Ciphertext Byte %02d: %02x \n",i,ciphertext[i]);
        printf("Plaintext Byte %02d: %02x \n",i,plaintext[i]);
    }

    // Reading round keys in reverse order
    for(uint8_t i = 0; i < 22; i++) {  // Block size 32 has only one round number option

        //printf("y_word - (%d) - %u\n", i, (unsigned int)y_word);
        //printf("x_word - (%d) - %u\n", i, (unsigned int)x_word);
        // Inverting rotations and using custom modular subtraction
        y_word = rotate_right((x_word ^ y_word), 2);
        x_word = rotate_left( (sub_mod((x_word ^ *(round_key_ptr + 21 - i)), y_word, 65535)), 7);

    }
    // Assemble Plaintext - Swapping plaintext words
    *word_ptr = y_word;
    word_ptr += 1;
    *word_ptr = x_word;
    return;
}

我已经有一段时间没有用C编写代码了,可能有一些错误。

最佳答案

考虑到repo的作者没有绕过编写C解密例程,我会先考虑C设置或加密例程的有效性。
与其从这里开始,不如看看一个正在工作的C实现:
https://github.com/tomasaazevedo/Speck_8-bit_C
https://github.com/yuehann/Simon_Speck
https://github.com/mysummergit/myssl/blob/master/demos/mycipher/speck.c

关于c - Blob 密码-C中的解密问题,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/44977145/

10-12 00:20
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