iOS/C Hmac+SHA256 Encryption

HmacSHA256 Encryption

#include <CommonCrypto/CommonDigest.h>
#include <CommonCrypto/CommonHMAC.h>

@interface ZRCommonCryption : NSObject
/**
 *  加密方式,MAC算法: HmacSHA256
 *
 *  @param plaintext 要加密的文本
 *  @param key       秘钥
 *
 *  @return 加密后的字符串
 */
+ (NSString *)hmac:(NSString *)plaintext withKey:(NSString *)key;

@end

@implementation ZRCommonCryption

+ (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;
}

@end