C语言分段进行MD5算法程序

以下是一个基于C语言的分段进行MD5算法的示例程序：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

#define LEFTROTATE(x, c) (((x) << (c)) | ((x) >> (32 - (c))))

void md5(uint8_t *initial_msg, size_t initial_len, uint8_t *digest) {
    // These vars will contain the hash
    uint32_t h0, h1, h2, h3;

    // Message (to prepare)
    uint8_t *msg = NULL;

    // Note: All variables are unsigned 32 bit and wrap modulo 2^32 when calculating

    // r specifies the per-round shift amounts
    uint32_t r[] = {
        7, 12, 17, 22,
        7, 12, 17, 22,
        7, 12, 17, 22,
        7, 12, 17, 22
    };

    // Use binary integer part of the sines of integers (Radians) as constants:
    const uint32_t k[] = {
        0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
        0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
        0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
        0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
        0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
        0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
        0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
        0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
        0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
        0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
        0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
        0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
        0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
        0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
        0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
        0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
    };

    // Initialize variables:
    h0 = 0x67452301;
    h1 = 0xEFCDAB89;
    h2 = 0x98BADCFE;
    h3 = 0x10325476;

    // Pre-processing:
    // append "1" bit to message
    // append "0" bits until message length in bits ≡ 448 (mod 512)
    // append length mod (2^64) to message
    int new_len, offset;
    for (new_len = initial_len + 1; new_len % (512 / 8) != 448 / 8; new_len++)
        ;

    msg = calloc(new_len + 8, 1); // also appends "0" bits
    memcpy(msg, initial_msg, initial_len);
    msg[initial_len] = 128; // append the "1" bit

    offset = new_len + 8 - 8; // append length in bits
    memcpy(msg + offset, &initial_len, 4); // assumes 4-byte integer
    // note: we're appending the length of the *original* message
    // NOT the padded message

    // Process the message in successive 512-bit chunks:
    // for each 512-bit chunk of message:
    int i;
    uint32_t *w;
    for (i = 0; i < new_len; i += (512 / 8)) {

        // break chunk into sixteen 32-bit words w[j], 0 ≤ j ≤ 15
        w = (uint32_t *)(msg + i);

        // Initialize hash value for this chunk:
        uint32_t a = h0;
        uint32_t b = h1;
        uint32_t c = h2;
        uint32_t d = h3;
        uint32_t f, g;

        // Main loop:
        for (int j = 0; j < 64; j++) {
            if (j < 16) {
                f = (b & c) | ((~b) & d);
                g = j;
            } else if (j < 32) {
                f = (d & b) | ((~d) & c);
                g = (5 * j + 1) % 16;
            } else if (j < 48) {
                f = b ^ c ^ d;
                g = (3 * j + 5) % 16;
            } else {
                f = c ^ (b | (~d));
                g = (7 * j) % 16;
            }

            uint32_t temp = d;
            d = c;
            c = b;
            b = b + LEFTROTATE((a + f + k[j] + w[g]), r[j]);
            a = temp;
        }

        // Add this chunk's hash to result so far:
        h0 += a;
        h1 += b;
        h2 += c;
        h3 += d;
    }

    // cleanup
    free(msg);

    // Produce the final hash value (big-endian):
    memcpy(digest, &h0, 4);
    memcpy(digest + 4, &h1, 4);
    memcpy(digest + 8, &h2, 4);
    memcpy(digest + 12, &h3, 4);
}

int main(int argc, char **argv) {
    uint8_t digest[16];
    char *msg = "The quick brown fox jumps over the lazy dog";

    md5(msg, strlen(msg), digest);

    for (int i = 0; i < 16; i++)
        printf("%02x", digest[i]);
    printf("\n");

    return 0;
}

该程序将消息拆分为512位的块，并对每个块进行MD5哈希计算。在处理前，还需要对消息进行预处理，包括附加“1”位、附加“0”位直到消息长度为448（模512）位、附加原始消息长度的二进制表示等。程序输出128位（16字节）的哈希值。