Re: Is there a hidden channel in X authentication?

From: David Wagner (dawat_private)
Date: Tue May 22 2001 - 09:48:18 PDT

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    Michael Wojcik  wrote:
    >In any case, it's easy enough to mask the time by using a hand-coded
    >comparison loop that always compares all the bytes and sets a flag if any of
    >them differ.
    
    A nice approach is to do what Unix password authentication does:
    Hash both inputs, and then check if the hashes are the same.  The latter
    comparison can be done with memcmp(), because the timing side-channel
    reveals nothing if the hash is one-way.
    



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