ietf-openpgp
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Re: Phil Zimmermann's suggestion - Implementation?

1999-04-13 14:48:52
On Tue, 13 Apr 1999, Werner Koch wrote:

But I think this is still the most simple solution and we should do
it.  A more sophisticated solution could be to put MDCs every n byte
into the data to help early detection of modification.  However this
has not much to do with offline encryption but with online protocols
like SSH.   So I suggest we keep the simple solution but use use a new
packet type for it.

This could be implemented with a new packet-stream type, so that the
partial packets could append X bytes.  Putting an MDC at the packetization
level is better than at the crypto level.  I.e

(1:4096)(4096:data)(MDC:20)...(1:17)(17:data)(MDC:20)

I think it is bad style to change a standard which already defines how
to handle different blocksizes (albeit with some conflicts).

Which is why I call it a different "method".  The spec already has
something for the existing method (PGP/CFB) with larger block sizes, and
my implementation is set up to handle these correctly, at least as far as
I have been able to verify.