Redirect URL Encryption issue

Hi,

I have an order page which needs to be integrated with Credit Card Payment solution. The pre-req is that the URL should be encrypted with AES_128.

I am not encountering any errors in the encryption anymore. However, its not being accepted by the third party and based on first analysis when I decryption the encrypted URL I get special characters

Any ideas why would this be happening ?

Decrypted Value = �j��l �Xg�չJ��"90&order_id=106&amount=44&currency=AED&redirect_url=www.ccavenue.ae

Code used for encryption

DECLARE

 l_redirect_url VARCHAR2(4000);

 encryption_type PLS_INTEGER :=

   DBMS_CRYPTO.ENCRYPT_AES128