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/