Finding encrytion algorithm

[Mike Rosing]

On Thu, 11 Jul 2002, Sandy Harris wrote:

> Doing this is only at worst 12 times harder than breaking a
> single known cipher. If some of your 12 breaks are easy, then
> total effort is much less than 12 times the hardest cipher.
> When we're talking about 2^40 steps to break a laughably weak
> cipher and > 2^100 for a good one, making it 12, or 1000,
> times harder is not a very interesting difference.

Yup.

> No. Any good algorithm should produce output that looks /exactly/
> like random noise, hence they should all look like each other.
>
> This may not be precisely true, but all decent algorithms will
> look random enough to make distinguishing quite difficult.

At the binary level with no headers, "good" algorithms should definitly
look alike.  There's always some data left by the implementation tho,
so in practice you've got some foothold.  But I'm willing to bet that
encrypting megabytes of 0x00000's with the same keys on different ciphers
whould show some kind of statistical foothold.  "looking" like random and
"being" random aren't the same.  Especially if you've got an army of
mathematicians to keep busy :-)

But since I've never actually done it, I don't know how big that army
needs to be.

Patience, persistence, truth,
Dr. mike