Re: Key update

Jakob wrote:
Use the cipher as a PRP e.g.

K'[i] = E_K(i)

Use K'[] as your chain of keys.

Tom

Did you mean use a counter "i" , in K'[i] = E_K(i), or did you mean
use a short seed?
If counter "i", what can the size of "i" be?
If seed, what can the size of seed be?

Don't top post.

And yes, encrypt a counter i (hint: this is CTR mode) and use the
outputs as your keys. you can just zero pad i to the size of an AES
(or whatever cipher) block size provided that K (your secret key) is
random. If it isn't, then you should pad i with a random IV (hint: CTR
mode).

Tom

.

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