hmac-sha1加密算法C源码示例

HMAC: Hash-based Message Authentication Code，即基于Hash的消息鉴别码

在各大开放平台大行其道的互联网开发潮流中，调用各平台的API接口过程中，无一例外都会用到计算签名值(sig值)。而在各种计算签名的方法中，经常被采用的就是HMAC-SHA1，现对HMAC-SHA1做一个简单的介绍：HMAC，散列消息鉴别码，基于密钥的Hash算法认证协议。实现原理为：利用已经公开的Hash函数和私有的密钥，来生成固定长度的消息鉴别码；SHA1、MD5等Hash算法是比较常用的不可逆Hash签名计算方法；BASE64，将任意序列的8字节字符转换为人眼无法直接识别的符号编码的一种方法；
相关依赖库是openssl，安装方法如下：apt-get install openssl   //Ubuntu 14.04yum -y install openssl-devel    //centos

下面提供两个源码示例:例子一:
//gcc -g hmac_sha1_demo3.c -o hmac_sha1_demo3 -lcrypto -std=c99

#include <stdio.h>
#include <string.h>
#include <openssl/hmac.h>

int main()
{
// The key to hash
char key[] = "012345678";

// The data that we're going to hash using HMAC
char data[] = "hello world";

unsigned char digest[EVP_MAX_MD_SIZE] = {'\0'};
unsigned int digest_len = 0;

// Using sha1 hash engine here.
// You may use other hash engines. e.g EVP_md5(), EVP_sha224, EVP_sha512, etc
HMAC(EVP_sha1(), key, strlen(key), (unsigned char*)data, strlen(data), digest, &digest_len);
printf("%s, len %u\n", digest, digest_len);

// Be careful of the length of string with the choosen hash engine. SHA1 produces a 20-byte hash value which rendered as 40 characters.
// Change the length accordingly with your choosen hash engine
char mdString[41] = {'\0'};
for(int i = 0; i < 20; i++)
sprintf(&mdString[i*2], "%02x", (unsigned int)digest[i]);

printf("HMAC digest: %s\n", mdString);

return 0;
}

例子二:
//gcc -g hmac_sha1_demo2.c -o hmac_sha1_demo2 -lcrypto --std=c99

#include <stdio.h>
#include <string.h>
#include <openssl/hmac.h>

int main() {
// The secret key for hashing
const char key[] = "012345678";

// The data that we're going to hash
char data[] = "hello world";

// Be careful of the length of string with the choosen hash engine. SHA1 needed 20 characters.
// Change the length accordingly with your choosen hash engine.
unsigned char* result;
unsigned int len = 20;

result = (unsigned char*)malloc(sizeof(char) * len);

HMAC_CTX ctx;
HMAC_CTX_init(&ctx);

// Using sha1 hash engine here.
// You may use other hash engines. e.g EVP_md5(), EVP_sha224, EVP_sha512, etc
HMAC_Init_ex(&ctx, key, strlen(key), EVP_sha1(), NULL);
HMAC_Update(&ctx, (unsigned char*)&data, strlen(data));
HMAC_Final(&ctx, result, &len);
HMAC_CTX_cleanup(&ctx);

printf("HMAC digest: ");

for (int i = 0; i != len; i++)
printf("%02x", (unsigned int)result[i]);

printf("\n");

free(result);

return 0;
}
运行截图:



参考文献:
[1].http://www.askyb.com/cpp/openssl-hmac-hasing-example-in-cpp/