iOS开发 - 需要加密key的SHA256和MD5加密

如果你们在加密的时候，后台告诉你，用哈希算法或者MD5算法，然后用加密key来加密，你可能会一脸懵逼，博主也是第一次听说哈希加密要用加密key，为了弥补下知识空缺，博主就在网上查找资料，结果找到了这个东西：消息摘要算法。

消息摘要算法

我们通常在遇到的时候会看到“HMAC”字眼，mac（Message Authentication Code，消息认证码算法）是含有密钥散列函数算法，兼容了MD和SHA算法的特性，并在此基础上加上了密钥。因此MAC算法也经常被称作HMAC算法。

关于HMAC算法，需要和SHA256结合起来的话，代码如下：

//如果需要用到SHA的其他加密方法，比如128，1就把里面的256字眼换成对应的数字即可

引入头文件
#import 
#import 

- (NSString *)hmac:(NSString *)plaintext withKey:(NSString *)key
{
    const char *cKey  = [key cStringUsingEncoding:NSASCIIStringEncoding];
    const char *cData = [plaintext cStringUsingEncoding:NSASCIIStringEncoding];
    unsigned char cHMAC[CC_SHA256_DIGEST_LENGTH];
    CCHmac(kCCHmacAlgSHA256, cKey, strlen(cKey), cData, strlen(cData), cHMAC);
    NSData *HMACData = [NSData dataWithBytes:cHMAC length:sizeof(cHMAC)];
    const unsigned char *buffer = (const unsigned char *)[HMACData bytes];
    NSMutableString *HMAC = [NSMutableString stringWithCapacity:HMACData.length * 2];
    for (int i = 0; i < HMACData.length; ++i){
        [HMAC appendFormat:@"%02x", buffer[i]];
    }

    return HMAC;
}

HMACMD5加密

//引入头文件
#import 

+ (NSString *)HMACMD5WithString:(NSString *)toEncryptStr WithKey:(NSString *)keyStr
{
    const char *cKey  = [keyStr cStringUsingEncoding:NSUTF8StringEncoding];
    const char *cData = [toEncryptStr cStringUsingEncoding:NSUTF8StringEncoding];
    const unsigned int blockSize = 64;
    char ipad[blockSize];
    char opad[blockSize];
    char keypad[blockSize];

    unsigned int keyLen = strlen(cKey);
    CC_MD5_CTX ctxt;
    if (keyLen > blockSize) {
        CC_MD5_Init(&ctxt);
        CC_MD5_Update(&ctxt, cKey, keyLen);
        CC_MD5_Final((unsigned char *)keypad, &ctxt);
        keyLen = CC_MD5_DIGEST_LENGTH;
    }
    else {
        memcpy(keypad, cKey, keyLen);
    }

    memset(ipad, 0x36, blockSize);
    memset(opad, 0x5c, blockSize);

    int i;
    for (i = 0; i < keyLen; i++) {
        ipad[i] ^= keypad[i];
        opad[i] ^= keypad[i];
    }

    CC_MD5_Init(&ctxt);
    CC_MD5_Update(&ctxt, ipad, blockSize);
    CC_MD5_Update(&ctxt, cData, strlen(cData));
    unsigned char md5[CC_MD5_DIGEST_LENGTH];
    CC_MD5_Final(md5, &ctxt);

    CC_MD5_Init(&ctxt);
    CC_MD5_Update(&ctxt, opad, blockSize);
    CC_MD5_Update(&ctxt, md5, CC_MD5_DIGEST_LENGTH);
    CC_MD5_Final(md5, &ctxt);

    const unsigned int hex_len = CC_MD5_DIGEST_LENGTH*2+2;
    char hex[hex_len];
    for(i = 0; i < CC_MD5_DIGEST_LENGTH; i++) {
        snprintf(&hex[i*2], hex_len-i*2, "%02x", md5[i]);
    }

    NSData *HMAC = [[NSData alloc] initWithBytes:hex length:strlen(hex)];
    NSString *hash = [[NSString alloc] initWithData:HMAC encoding:NSUTF8StringEncoding];
    return hash;
}

参考博客：
http://supershll.blog.163.com/blog/static/37070436201411522220174/
http://www.jianshu.com/p/98e376b66a26

对于hmac的解析推荐百度词条，了解即可。
http://baike.baidu.com/link?url=n6Fe5etGJFBvj-MXE77ohyet-Nh0Dwl4SQ1GApHC3THe3zQMfAT-6pjtpCMr5vSKd7TOQYr2SHnZJ0B3RgQdqq