double encryption

Frank Tobin
Tue Jun 11 05:29:01 2002

On Tue, 11 Jun 2002, Volker Gaibler wrote:

> A DoubleDES cipher (encrypting two times with SingleDES and two
> different keys) has an effective key size of only 1 bit more than
> SingleDES. This is not really stronger than the single encryption - and
> DES is a really good cipher (only it's key size is much too small).
> There are even (theoretical!) examples where cascaded encryption can
> weaken a cipher. But that's really theoretical.

Using the same cipher twice is one thing, but how about two different 
ciphers?  At best, you might get the benefit if twice the keylength (if 
you use different keys), and assuredness that if one cipher breaks, your 
message is still safe.

Frank Tobin