[Cryptography] Key meshing (Re: [Crypto-practicum] Retire all 64-bit block ciphers.)

[Bill Frantz]

On 8/30/16 at 9:22 AM, phill at hallambaker.com (Phillip 
Hallam-Baker) wrote:

>What I don't understand is why the various symmetric cipher modes we have
>keep the key fixed and modify the data.
>
>...
>
>The main reason for not doing this seems to be that the key schedule has to
>be recalculated and that was expensive for DES. But that shouldn't be a
>major problem on a modern CPU.

I think it is the cost of recalculating the key schedule. Some 
ciphers, e.g. Blowfish, deliberately have expensive key 
schedules to deter exhaustive search attacks.

Cheers - Bill

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