C语言实现rsa数字签名代码和验签

RSA数字签名是一种常用的数字签名算法，实现代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/rsa.h>
#include <openssl/pem.h>

// 生成RSA密钥对
int generate_key(char *pub_key_file, char *pri_key_file, int key_len)
{
    int ret = 0;
    RSA *rsa = NULL;
    BIGNUM *bne = NULL;
    BIO *bp_public = NULL, *bp_private = NULL;
    char *pub_key = NULL, *pri_key = NULL;

    // 生成RSA密钥对
    bne = BN_new();
    ret = BN_set_word(bne, RSA_F4);
    if (ret != 1) {
        printf("BN_set_word failed\n");
        return -1;
    }

    rsa = RSA_new();
    ret = RSA_generate_key_ex(rsa, key_len, bne, NULL);
    if (ret != 1) {
        printf("RSA_generate_key_ex failed\n");
        return -1;
    }

    // 将密钥对输出到文件
    bp_public = BIO_new(BIO_s_file());
    bp_private = BIO_new(BIO_s_file());

    ret = BIO_write_filename(bp_public, pub_key_file);
    if (ret <= 0) {
        printf("BIO_write_filename public failed\n");
        return -1;
    }

    ret = PEM_write_bio_RSAPublicKey(bp_public, rsa);
    if (ret != 1) {
        printf("PEM_write_bio_RSAPublicKey failed\n");
        return -1;
    }

    ret = BIO_write_filename(bp_private, pri_key_file);
    if (ret <= 0) {
        printf("BIO_write_filename private failed\n");
        return -1;
    }

    ret = PEM_write_bio_RSAPrivateKey(bp_private, rsa, NULL, NULL, 0, NULL, NULL);
    if (ret != 1) {
        printf("PEM_write_bio_RSAPrivateKey failed\n");
        return -1;
    }

    RSA_free(rsa);
    BN_free(bne);
    BIO_free_all(bp_public);
    BIO_free_all(bp_private);

    return 0;
}

// RSA数字签名
int rsa_sign(char *data, int data_len, char *pri_key_file, char *signature, int *sig_len)
{
    int ret = 0;
    RSA *rsa = NULL;
    FILE *fp = NULL;
    char *pri_key = NULL;

    // 读取密钥文件
    fp = fopen(pri_key_file, "rb");
    if (fp == NULL) {
        printf("open private key file failed\n");
        return -1;
    }

    rsa = PEM_read_RSAPrivateKey(fp, &rsa, NULL, NULL);
    if (rsa == NULL) {
        printf("PEM_read_RSAPrivateKey failed\n");
        return -1;
    }

    // RSA数字签名
    ret = RSA_sign(NID_sha256, (unsigned char *)data, data_len, (unsigned char *)signature, (unsigned int *)sig_len, rsa);
    if (ret != 1) {
        printf("RSA_sign failed\n");
        return -1;
    }

    RSA_free(rsa);
    fclose(fp);

    return 0;
}

// RSA数字验签
int rsa_verify(char *data, int data_len, char *pub_key_file, char *signature, int sig_len)
{
    int ret = 0;
    RSA *rsa = NULL;
    FILE *fp = NULL;
    char *pub_key = NULL;

    // 读取密钥文件
    fp = fopen(pub_key_file, "rb");
    if (fp == NULL) {
        printf("open public key file failed\n");
        return -1;
    }

    rsa = PEM_read_RSAPublicKey(fp, &rsa, NULL, NULL);
    if (rsa == NULL) {
        printf("PEM_read_RSAPublicKey failed\n");
        return -1;
    }

    // RSA数字验签
    ret = RSA_verify(NID_sha256, (unsigned char *)data, data_len, (unsigned char *)signature, sig_len, rsa);
    if (ret != 1) {
        printf("RSA_verify failed\n");
        return -1;
    }

    RSA_free(rsa);
    fclose(fp);

    return 0;
}

使用示例：

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

int main(int argc, char *argv[])
{
    int ret = 0;
    char *pub_key_file = "rsa_public_key.pem";
    char *pri_key_file = "rsa_private_key.pem";
    char *data = "Hello, World!";
    char signature[1024] = {0};
    int sig_len = 0;

    // 生成RSA密钥对
    ret = generate_key(pub_key_file, pri_key_file, 2048);
    if (ret != 0) {
        printf("generate_key failed\n");
        return -1;
    }

    // RSA数字签名
    ret = rsa_sign(data, strlen(data), pri_key_file, signature, &sig_len);
    if (ret != 0) {
        printf("rsa_sign failed\n");
        return -1;
    }

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

    // RSA数字验签
    ret = rsa_verify(data, strlen(data), pub_key_file, signature, sig_len);
    if (ret != 0) {
        printf("rsa_verify failed\n");
        return -1;
    }

    printf("verify success\n");

    return 0;
}