[Cryptography] crypto standards and principles

[Kent Borg]

On 02/03/2015 07:46 PM, Tom Mitchell wrote:
> Many times we talk about a key or method that had 2^64 or 2^1024
> or pick a number.   When two methods are possible an attacker must
> attack 2^65 different permutations or 2^1025. Sometimes doubling
> the effective key length doubles a search space. Expanding the method
> list to one of any vastly complicates an attack.

Sounds fishy; an extra bit or two of the key could be used to select 
among key methods and make things much stronger! Seems too good an idea 
to pass up, why don't we do that? Why is AES-256 not, say, AES-260 with 
4-bits used to select among different algorithm variations?

-kb