Subject: newmodes-03 buglet: *-ctr modes' blocksizes?

From: der Mouse <[email-masked]>
Date: Mon, 30 May 2005 02:18:16 -0400 (EDT)

Looking at newmodes-03, I see various *-ctr modes described.  But they
are basically stream ciphers, and as such, do not really have a
blocksize any more than (say) arcfour does.

But for interoperability everyone has to agree on what their blocksize
is for purposes of ssh use.  For the -ctr modes I've already
implemented (blowfish-ctr and 3des-ctr) this hasn't mattered because
their "native" blocksize is 64 bits, and strema ciphers are treated as
having 64-bit blocks for purposes of ssh's stream blocking.  But now I
want to do the aes*-ctr modes, and this suddenly matters.

So, I think newmodes-03 needs to be updated to clarify this: do these
*-ctr modes run as stream ciphers, blocking the data stream to 64-bit
blocks like any stream cipher, or do they run as block ciphers (which
happen to be implemented as stream ciphers) with block sizes copied
from their underlying block algorithms?  (Or something else?)

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From: der Mouse <[email-masked]>
Date: Mon, 30 May 2005 02:29:27 -0400 (EDT)

> So, I think newmodes-03 needs to be updated to clarify this: [...]

Never mind, I apparently can't read.  "The block size is 8 bytes."
"The block size is 16 bytes."

Duh.

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