sign.m

+ (NSString *)signString:(NSString *)paramString {
    NSData *paramData = [paramString dataUsingEncoding:NSUTF8StringEncoding];
    NSData *secretData = [kMessagePetzAPISecret dataUsingEncoding:NSUTF8StringEncoding];
    NSMutableData *sigData = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
    CCHmac(kCCHmacAlgSHA256, secretData.bytes, secretData.length, paramData.bytes, paramData.length, sigData.mutableBytes);
    
    return [sigData hexadecimalString];
}