This is my function. First println print correct hash to console but in the next row program crashes. Can you help me? func sha256(string: NSString) -> NSString { var data : NSData! = string.dataUsingEncoding(NSUTF8StringEncoding) var hash = [UInt8](count: Int(CC_SHA256_DIGEST_LENGTH), repeatedValue: 0) CC_SHA256(data.bytes, CC_LONG(data.length), &hash) let res = NSData(bytes: hash, length: Int(CC