Почему Java и Objective-C HMASHA256 дают разные результаты?

Question

Я пытаюсь преобразовать следующий код Java в Objective-C. Я пробовал некоторые функции HMASHA256, но возвращаемая подпись в конце возвращает другую строку.

JAVA

public static byte[] hmac256(byte[] key, String msg) throws Exception {
     Mac mac = Mac.getInstance("HmacSHA256");
     SecretKeySpec secretKeySpec = new SecretKeySpec(key,mac.getAlgorithm());
     mac.init(secretKeySpec);
     return mac.doFinal(msg.getBytes(UTF8));
}

byte[] secretDate = hmac256(("TC3" + SECRET_KEY).getBytes(UTF8), date);
byte[] secretService = hmac256(secretDate, service);
byte[] secretSigning = hmac256(secretService, "tc3_request");
String signature = DatatypeConverter.printHexBinary(hmac256(secretSigning, stringToSign)).toLowerCase();
System.out.println(signature);

Objective-C

- (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;
}

NSString * date = [NSString stringWithFormat:@"TC3%@",SECRET_KEY];    
NSString * secretDate = [self hmac:dateString withKey:date];
NSString * secretService = [self hmac:service withKey:secretDate];
NSString * secretSigning = [self hmac:@"tc3_request" withKey:secretService];
NSString * signatureString = [self hmac:stringToSign withKey:secretSigning];