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 <CommonCrypto/CommonHMAC.h>
#import <CommonCrypto/CommonCryptor.h>

- (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 <CommonCrypto/CommonDigest.h>

+ (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