Help with decrypting a URL from external source using JWS

[YenGar]

Hello all, 

I am struggling a bit to accomplish decrypting a URL that is sent through an embedded link in an external site. The URL is encrypted with AES256 algorithm. It is a pure symmetric encryption as there is a shared encryption key. I'm having a hard time setting up the decryption part using a library. I know I can add a library as a script include and call it to decrypt the url but just not sure where to begin. 

The thought process is: 

- User clicks button on external site

- User is re-directed to a servicenow catalog item, the URL parameters carries encrypted data from the external site

- servicenow is supposed to use the shared key to decrypt the url parameters and put them in specific fields in the catalog item (note: i can grab parameters through a client script and drop them in the variable fields easily but since it is encrypted, i have to decrypt first and then put them in the specific fields). 

Any guidance on where to start is highly appreciated. 

Thank you, 

Yen

[YenGar]

Thanks Isaac. Yea, we're still figuring it out. 

Yen

[dsf3]

@YenGar Did you found any solution ?? I am also having similar requirement but not found any solution in servicenow.