Hi MuthuKumaran, Thank you for you response.
I had tried this policy earlier which is available in Github (Ref) but it was not working and was throwing below error
"CS1061-'byte[]' does not contain a definition for 'Encrypt' and no accessible extension method 'Encrypt' accepting a first argument of type 'byte[]' could be found (are you missing a using directive or an assembly reference?)".
I revalidated my policy and after doing some minor changes it started working. Pls check below latest code. Thanks for you clue.
byte[] IV = System.Text.Encoding.UTF8.GetBytes("5183666c72eec9e4");
byte[] Key = System.Text.Encoding.UTF8.GetBytes("bf3c199c2470cb477d907b1e0917c17b");
byte[] textinBytes = Convert.FromBase64String("t/esIUJIgM5TU5+EsZQASCiAYWrcvMGyBvmvaHcdtdU=");
var decryptedBytes = textinBytes.Decrypt("Aes", Key, IV);
return decryptedBytes;