Losing the Code War by Stephen Budiansky

[Ben Laurie]

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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