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Re: passwd hashing algorithm
From: dennisg () CyberSAFE COM (Dennis Glatting)
Date: Sat, 15 Apr 1995 08:20:40 -0700


Date: Fri, 14 Apr 1995 12:30:05 -0400
Sender: owner-bugtraq () fc net


    From: Adam Shostack <adam () bwh harvard edu>
    Date: Thu, 13 Apr 1995 13:23:03 -0400 (EDT)


    Doing to 3des means you (roughly) triple the attack time, which
    means that in about 2 years, we'll be back where we are today.


This does not fit with my understanding of 3DES.  I thought
that 3DES effectively tripled the key size, i. e. you have
to derive three DES keys simultaneously in order to
crack.  This should make the attack time significantly
greater than 3 times the DES attack time.  If it is merely
the case of deriving three keys independently, 3DES is
already useless.  Since people often compare the
security of 3DES to IDEA, I don't think that this is the
case. 




Two key 3DES has an "effective" key length of 57 bits.
Three key is 112 bits. Depending upon how you implement
3DES in hardware the encryption time is one to three times
of single DES. In software it is 3x. 



-dpg



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