c语言写sha1算法

以下是使用C语言实现SHA1算法的示例代码：

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

#define SHA1_BLOCK_SIZE 64
#define SHA1_DIGEST_SIZE 20

typedef struct {
    uint32_t state[5];
    uint32_t count[2];
    uint8_t buffer[SHA1_BLOCK_SIZE];
} SHA1_CTX;

void sha1_transform(SHA1_CTX *ctx, const uint8_t *data) {
    uint32_t a, b, c, d, e, f, k, temp;
    uint32_t w[80];

    for (int i = 0; i < 16; i++) {
        w[i] = ((uint32_t) data[i * 4] << 24) |
               ((uint32_t) data[i * 4 + 1] << 16) |
               ((uint32_t) data[i * 4 + 2] << 8) |
               ((uint32_t) data[i * 4 + 3]);
    }

    for (int i = 16; i < 80; i++) {
        w[i] = (w[i - 3] ^ w[i - 8] ^ w[i - 14] ^ w[i - 16]);
        w[i] = (w[i] << 1) | (w[i] >> 31);
    }

    a = ctx->state[0];
    b = ctx->state[1];
    c = ctx->state[2];
    d = ctx->state[3];
    e = ctx->state[4];

    for (int i = 0; i < 80; i++) {
        if (i < 20) {
            f = (b & c) | ((~b) & d);
            k = 0x5A827999;
        } else if (i < 40) {
            f = b ^ c ^ d;
            k = 0x6ED9EBA1;
        } else if (i < 60) {
            f = (b & c) | (b & d) | (c & d);
            k = 0x8F1BBCDC;
        } else {
            f = b ^ c ^ d;
            k = 0xCA62C1D6;
        }

        temp = ((a << 5) | (a >> 27)) + f + e + k + w[i];
        e = d;
        d = c;
        c = (b << 30) | (b >> 2);
        b = a;
        a = temp;
    }

    ctx->state[0] += a;
    ctx->state[1] += b;
    ctx->state[2] += c;
    ctx->state[3] += d;
    ctx->state[4] += e;
}

void sha1_init(SHA1_CTX *ctx) {
    ctx->state[0] = 0x67452301;
    ctx->state[1] = 0xEFCDAB89;
    ctx->state[2] = 0x98BADCFE;
    ctx->state[3] = 0x10325476;
    ctx->state[4] = 0xC3D2E1F0;
    ctx->count[0] = 0;
    ctx->count[1] = 0;
}

void sha1_update(SHA1_CTX *ctx, const uint8_t *data, size_t len) {
    uint32_t i, index = (uint32_t) ((ctx->count[0] >> 3) & 63);

    ctx->count[0] += (uint32_t) (len << 3);
    if (ctx->count[0] < (uint32_t) (len << 3)) {
        ctx->count[1]++;
    }
    ctx->count[1] += (uint32_t) (len >> 29);

    for (i = 0; i < len; i++) {
        ctx->buffer[index++] = data[i];
        if (index == 64) {
            sha1_transform(ctx, ctx->buffer);
            index = 0;
        }
    }
}

void sha1_final(SHA1_CTX *ctx, uint8_t *digest) {
    uint32_t i, index = (uint32_t) ((ctx->count[0] >> 3) & 63);
    uint8_t finalcount[8];

    for (i = 0; i < 8; i++) {
        finalcount[i] = (uint8_t) ((ctx->count[(i >= 4 ? 1 : 0)] >> ((3 - (i & 3)) * 8)) & 255);
    }

    uint8_t padding[SHA1_BLOCK_SIZE] = {0x80};
    sha1_update(ctx, padding, 1);

    while (index < 56) {
        sha1_update(ctx, padding, 1);
        index++;
    }

    sha1_update(ctx, finalcount, 8);

    for (i = 0; i < SHA1_DIGEST_SIZE; i++) {
        digest[i] = (uint8_t) ((ctx->state[i >> 2] >> ((3 - (i & 3)) * 8)) & 255);
    }
}

void sha1(const uint8_t *data, size_t len, uint8_t *digest) {
    SHA1_CTX ctx;
    sha1_init(&ctx);
    sha1_update(&ctx, data, len);
    sha1_final(&ctx, digest);
}

int main() {
    uint8_t data[] = "hello world";
    uint8_t digest[SHA1_DIGEST_SIZE];

    sha1(data, strlen((char *) data), digest);

    printf("SHA1 digest: ");
    for (int i = 0; i < SHA1_DIGEST_SIZE; i++) {
        printf("%02x", digest[i]);
    }
    printf("\n");

    return 0;
}

此代码使用了结构体 `SHA1_CTX` 来存储 SHA1 计算过程中的状态信息，包括 5 个 32 位状态变量、64 位计数器和 64 字节缓冲区。`sha1_transform` 函数实现 SHA1 算法的核心部分，将每个 64 字节的数据块进行处理；`sha1_init` 函数初始化状态变量和计数器；`sha1_update` 函数将数据块分块处理；`sha1_final` 函数用于完成 SHA1 计算并输出结果；`sha1` 函数是一个简单的封装，用于直接计算数据的 SHA1 散列值。