#import "AlgorithmManager.h"
#import <CommonCrypto/CommonCrypto.h>

@implementation AlgorithmManager


+ (NSString *)signWithHmacSHA256:(NSString *)input withKey:(NSString *)key{


    const char *cKey  = [key cStringUsingEncoding:NSASCIIStringEncoding];
    const char *cData = [input cStringUsingEncoding:NSASCIIStringEncoding];
    
    unsigned char cHMAC[CC_SHA256_DIGEST_LENGTH];
    
    CCHmac(kCCHmacAlgSHA256, cKey, strlen(cKey), cData, strlen(cData), cHMAC);
    
    NSData *HMACData = [[NSData alloc] initWithBytes:cHMAC length:sizeof(cHMAC)];
    
    const unsigned char *buffer = (const unsigned char *)[HMACData bytes];
    NSString *HMAC = [NSMutableString stringWithCapacity:HMACData.length * 2];
    
    for (int i = 0; i < HMACData.length; ++i)
        HMAC = [HMAC stringByAppendingFormat:@"%02lx", (unsigned long)buffer[i]];
    
    return HMAC;

}

@end

HmacSHA256 實現原理與HmacSHA1原理一樣，只需要設置兩個參數即可。

1. CC_SHA1_DIGEST_LENGTH －> CC_SHA256_DIGEST_LENGTH
2. kCCHmacAlgSHA1 －>kCCHmacAlgSHA256

同理 ,其它類型也可以設置。類型如下：

enum {
    kCCHmacAlgSHA1,
    kCCHmacAlgMD5,
    kCCHmacAlgSHA256,
    kCCHmacAlgSHA384,
    kCCHmacAlgSHA512,
    kCCHmacAlgSHA224
};