Re: On IVs



Ivan Voras wrote:
>My question is: are those pieces of data interchangable, in the sense
>that using a secret key and well-known (e.g. constant, predefined,
>transmitted) IV is as secure as using a well-known key and secret IV (on
>both sides)? In other words, if the key and IV are swapped in usage.

Nope, they're not the same. The latter (using a well-known key)
is 100% insecure.

By the way, most modes of operation require IVs to be random and
non-repeating, not constant and predefined.

I wouldn't suggest making up variations on the standard modes.
Just do what the standard says (unless you know enough cryptography
to safely deviate from the standard -- which most people don't).
.