Decrypted String always returning Null - swift

Question

Data fetched from server using
var request = var request = URLRequest(url: URL(string: "http://www.example.com/test.php")!)
request.httpMethod = "POST"
let akey:String = txt_key.stringValue;
let email:String = txt_email.stringValue
let VAL:String="test"
var data="blah"
let postString = data
request.httpBody = postString.data(using: .utf8)
let task = URLSession.shared.dataTask(with: request) { data, response, error in
guard let data = data, error == nil else { /
print("error=\(error)")
return
}
if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode != 200 { /
print("statusCode should be 200, but is \(httpStatus.statusCode)")
print("response = \(response)")
}
let responseString = String(data: data, encoding: .utf8)
print(responseString)
}
task.resume()
Decryption using
func aesDecrypt(key:String, iv:String, options:Int = kCCOptionPKCS7Padding) -> String? {
if let keyData = key.data(using: String.Encoding.utf8),
let data = NSData(base64Encoded: self, options: .ignoreUnknownCharacters),
let cryptData = NSMutableData(length: Int((data.length)) + kCCBlockSizeAES128) {
let keyLength = size_t(kCCKeySizeAES128)
let operation: CCOperation = UInt32(kCCDecrypt)
let algoritm: CCAlgorithm = UInt32(kCCAlgorithmAES128)
let options: CCOptions = UInt32(options)
var numBytesEncrypted :size_t = 0
let cryptStatus = CCCrypt(operation,
algoritm,
options,
(keyData as NSData).bytes, keyLength,
iv,
data.bytes, data.length,
cryptData.mutableBytes, cryptData.length,
&numBytesEncrypted)
if UInt32(cryptStatus) == UInt32(kCCSuccess) {
cryptData.length = Int(numBytesEncrypted)
let unencryptedMessage = String(data: cryptData as Data, encoding:String.Encoding.utf8)
return unencryptedMessage
}
else {
return nil
}
}
return nil
}
Even when responseString is not null,The following code always returns
optional("")
let unencode = String(describing: responseString!).aesDecrypt(key: "123456789012asdsadasd", iv: "iv-salt-string--")
Why is this happening ? Please advice.

Answer 1

Per MartinR's comment:
I have verified that "JDoNBXk21oJ9x15Bkv12uw==" is exactly the result of encrypting an empty string with your key and iv. The error is in your PHP script, not in the Swift code.
Therefore you need to resolve the error on the server.