xcode ios HMAC SHA 256 hashing

Question

So I\'m trying to figure out how to do a hmacshad256 hash on ios as that\'s the hash I did for the wcf service api I made. I\'ve been trying to look for some info about it but w

Answer 1

+ (NSString *)hmacSHA256EncryptString{


    NSString * parameterSecret = @"input secret key";
    NSString *plainString = @"input encrypt content string";
    const char *secretKey  = [parameterSecret cStringUsingEncoding:NSUTF8StringEncoding];
    const char *plainData = [plainString cStringUsingEncoding:NSUTF8StringEncoding];
    unsigned char cHMAC[CC_SHA256_DIGEST_LENGTH];
    CCHmac(kCCHmacAlgSHA256, secretKey, strlen(secretKey), plainData, strlen(plainData), cHMAC);
    NSData *HMACData = [NSData dataWithBytes:cHMAC length:sizeof(cHMAC)];
    const unsigned char *bufferChar = (const unsigned char *)[HMACData bytes];
    NSMutableString *hmacString = [NSMutableString stringWithCapacity:HMACData.length * 2];
    for (int i = 0; i < HMACData.length; ++i){
        [hmacString appendFormat:@"%02x", bufferChar[i]];
    }
    return hmacString;
    
}

Answer 2

Here is the solution I'm submitting that I put together from other answers on the matter:

This is easily adapted to other hash types by changing CC_SHA256_DIGEST_LENGTH and kCCHmacAlgSHA256.

If you're interested in doing that, check out the CommonDigest.h file within the CommonCrypto library.

#import <Foundation/Foundation.h>
#import <CommonCrypto/CommonCrypto.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;
}

This has been tested on iOS 8.x and iOS 7.x

Answer 3

NSString * parameters = @"string to hash"
NSString *salt = @"saltStringHere";
NSData *saltData = [salt dataUsingEncoding:NSUTF8StringEncoding];
NSData *paramData = [parameters dataUsingEncoding:NSUTF8StringEncoding];
NSMutableData* hash = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH ];
CCHmac(kCCHmacAlgSHA256, saltData.bytes, saltData.length, paramData.bytes, paramData.length, hash.mutableBytes);
NSString *base64Hash = [hash base64Encoding];

and also

#import <CommonCrypto/CommonHMAC.h>

Since base64Encoding is deprecated from iOS 7.0, the last line should be:

NSString *base64Hash = [hash base64EncodedStringWithOptions:0];