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[Re:] Interesting but vulnerable scheme for tokenless auth
From: Chris <info () delsec net>
Date: Wed, 26 Apr 2006 20:06:39 -0700

Glenn,

There are a few parts of this I am confused on.

In the cert is a private key. If the system were required to contact a 
"backend" server first, passing it perhaps a cipher containing its
serial number encrypted with its private key and its identity, the 

When you say pass a 'cipher' do you mean pass a message? And if you mean
pass a message then a  public/private crypto system would encrypt this
message using the backend servers public key, not its own private key.
Or perhaps I have misread your posting.

server could send back a (hopefully unique to that cert) decryption key 
that would decrypt the private key, allowing its use; the code at the PC 
would need to erase the cleartext private key when done. The server 

Sending of any keys over the air like this is dangerous, thats what
makes public/private crypto systems good. The only drawback is you need
a good PKI to support those users and be the CA. The CA is the only
authority the system should 'trust' when it comes to certificate
validation and revocation. Which means a second 'backend' server may
not fit well into this picture. 

could check the serial number matched the "identity" (it would have the 
public key) to prevent a simple search of the server for these 
encrypting keys.

I am not sure I understand this last part, please elaborate.

----------------------------------------
Chris 
Key ID: 7E8DE44E 
info () delsec net
----------------------------------------



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