Decrypt a string using PAD

[Nived_Nambiar]

Hi everyone,

I have a question, how to decrypt a string using AES GCM algorithm via power automate desktop ?

[Kaif_Siddique]

Try this:

SET strVal TO $'''Power Automate'''
Cryptography.EncryptText.EncryptTextWithAES Encoding: Cryptography.EncryptionEncoding.Unicode TextToEncrypt: strVal EncryptionKey: P'AQAAANCMnd8BFdERjHoAwE/Cl+sBAAAAYzwEO1cfH0CvaLEw5CgHAgQAAAACAAAAAAADZgAAwAAAABAAAAA0lxBdhorWQpIZzYVTpII+AAAAAASAAACgAAAAEAAAADjJe7qJVPXDgIQjXv6e2dQQAAAAi5oZd0lgPHVqjIxH6Bh/iRQAAAABDgKOuNIFNGOL3JdOj5vPhnP05Q==' PaddingMode: Cryptography.PaddingMode.PKCS7 KeySize: Cryptography.AESKeySize.Bits256 EncryptedText=> EncryptedText
Cryptography.DecryptText.DecryptTextWithAES Encoding: Cryptography.EncryptionEncoding.Unicode TextToDecrypt: EncryptedText DecryptionKey: P'AQAAANCMnd8BFdERjHoAwE/Cl+sBAAAAYzwEO1cfH0CvaLEw5CgHAgQAAAACAAAAAAADZgAAwAAAABAAAAAQAX0fYP/sEiZOkK/8XXUmAAAAAASAAACgAAAAEAAAAKdUtkXrqT4Tl0N2ucDddxMQAAAA8v5X65nioky/W6Vz4gZ8axQAAAAzmQxEB4h0uGp8WRCkjzG7sk0roQ==' Padding: Cryptography.PaddingMode.PKCS7 KeySize: Cryptography.AESKeySize.Bits256 DecryptedText=> DecryptedText

Encryption key is Direct password input. Change to desire password.

Regards

Kaif

[Nived_Nambiar]

Hi @Kaif_Siddique 

sorry for late response, actually this did not help me up. 

Currently i already have encrypted string which i need to decrypt, key is already provided as well. 

You can refer the website https://botsdna.com/RemoteDesktop/

to try around 

Here copy the secure string from any of cells from Encrypted Password column and you will get the secure code string which needs to decrypted.

I tried different approaches but still not get out how to solve this question. I have developed the same use case mentioned in UiPath, there we can decrypt using an activity easily, here i am not able to do same 

@Agnius  requesting you also too have a look on this as well 🙂

[Agnius]

It seems like UiPath applies some parameters behind the scenes that must be explicitly stated in PAD, such as the padding, the initialization vector, the key size, the encoding, etc. I've tried various combinations to de-crypt one of those passwords, as well as watching the YouTube video where they demonstrate this in UiPath to actually encrypt a sample password they actually provided in the video and see if I can get the same string, but I couldn't get it to work properly.

It just seems like we're missing some data in the task that is needed for PAD to be able to handle this.

[Nived_Nambiar]

Hi @Agnius 

You are right , I have tried this first in UiPath and it was easy to decrypt there,But when samething tried it is asking for some other parameters which i don't have the idea so i did a research with respect to this but could not find lead for this 😞

[kinuasa]

The following is a simple test code, I have confirmed that it can be decrypted.

using System.Text;
using System.Security.Cryptography;

const int SALT_SIZE = 8;
const int IV_SIZE = 12;
const int TAG_SIZE = 16;
const int KEY_SIZE = 32;

var data = Convert.FromBase64String("RZwzrinqo6UbvDkZMeC6LWaqRSXmbKgaPtTD/9nluImgrYNflbK2wkW8biU=");
var pass = Encoding.UTF8.GetBytes("botsDNA");

var saltBytes = new byte[SALT_SIZE];
var IV = new byte[IV_SIZE];
var tag = new byte[TAG_SIZE];
var encryptedData = new byte[data.Length - SALT_SIZE - IV_SIZE - TAG_SIZE];
Array.Copy(data, 0, saltBytes, 0, SALT_SIZE);
Array.Copy(data, SALT_SIZE, IV, 0, IV_SIZE);
Array.Copy(data, SALT_SIZE + IV_SIZE, encryptedData, 0, encryptedData.Length);
Array.Copy(data, SALT_SIZE + IV_SIZE + encryptedData.Length, tag, 0, TAG_SIZE);

using var r = new Rfc2898DeriveBytes(pass, saltBytes, 10000);
using var aes = new AesGcm(r.GetBytes(KEY_SIZE));
var decryptedBytes = new byte[encryptedData.Length];
aes.Decrypt(IV, encryptedData, tag, decryptedBytes);

Console.WriteLine(Encoding.UTF8.GetString(decryptedBytes));

When running with Power Automate for desktop, I guess the "Run .NET script" action or Custom actions could be used.