[Cryptography] BLAKE2: "Harder, Better, Faster, Stronger" Than MD5

[Sandy Harris]

On Tue, Mar 25, 2014 at 6:08 PM,  <tpb-crypto at laposte.net> wrote:

> Since I'm merely a code monkey and not a cryptographer, all that I can do is encrypt a stream and then apply another level of encryption over it by using a different algorithm.
>
> I know you guys don't like this approach, yet I have got no references on how to make it better. All I know is that if the first layer is broke, the would-be attacker will get another jumbled stream and will have to start all over again.

One thing to worry about is whether that exposes your system to a
meet-in-the-middle attack. e.g DES has a 56-bit key so one might
expect that applying it twice would give 2^112 security and there is
probably some clever method for which that is true. The obvious method
-- just apply it twice with two different keys -- gives only 2^57.
That is why triple DES is widely used & double DES not.

The attack works for ciphers other than DES and for two different
ciphers naively combined. One reference is:
http://en.citizendium.org/wiki/Meet-in-the-middle_attack