How can I get the encryption type from PREAUTH error reply?

[Surendra Babu Ande]

Hello Krbdev,
 
I am working on the preauth feature. 
What is preauthentication feature?: The client sends a pre-authentication request (In ASREQ pkt) with client's timestamp and user's password encrypted messages.
 
The question is: what encryption type to be used to send the encrypted message? If the client side enctype is not supported at KDC server, it will throw PREAUTH failed error.
 
To overcome this issue, we need to capture the encryption type from the Preauth errror reply message. With that KDc supported enctype, we will encrypt the message send it to KDC server.
 
Now my question is : HOW TO EXTRACT THE SERVER's ENCRYPTION TYPE FROM THE PREAUTH ERROR REPLY MESSAGE? 
 
Please let me know your opinion on this? How to extract the enctype from the preauth reply message?
 
(In KDC server code: Get_in_tkt.c file? Any hints? How to extract it?)
Thank you,
-Surendra
 
 
 

		
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