[10353] in cryptography@c2.net mail archive
Re: Losing the Code War by Stephen Budiansky
daemon@ATHENA.MIT.EDU (Ben Laurie)
Sat Feb 2 11:33:35 2002
Message-ID: <3C5BF03C.115B9450@algroup.co.uk>
Date: Sat, 02 Feb 2002 13:57:16 +0000
From: Ben Laurie <ben@algroup.co.uk>
MIME-Version: 1.0
To: marius <marius.corbu@analog.com>
Cc: cryptography@wasabisystems.com
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marius wrote:
>
> "But there was an utterly trivial fix that DES users could employ if
> they were worried
> about security: they could simply encrypt each message twice, turning
> 56-bit DES into 112-bit DES, and squaring the number of key sequences
> that
> a code breaker would have to try. Messages could even be encrypted
> thrice;
> and, indeed, many financial institutions at the time were already using
> "Triple DES." "
>
> Not quite true. Encrypting each message twice would not increase the
> "effective" key size to 112 bits.
> There is an attack named "meet in the middle" which will make the
> effective key size to be just 63 bits.
?? 56 bits "plus a little", surely.
Cheers,
Ben.
--
http://www.apache-ssl.org/ben.html http://www.thebunker.net/
"There is no limit to what a man can do or how far he can go if he
doesn't mind who gets the credit." - Robert Woodruff
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