PGP encryption: block or stream cipher?

David Shaw dshaw at
Tue Nov 6 23:43:11 CET 2007

On Tue, Nov 06, 2007 at 09:20:31PM +0100, Sven Radde wrote:
> Hi!
> Jim Cook schrieb:
> > Does anyone know which type of cipher is used?
> GnuPG uses a number of block ciphers in a variant of CFB mode.
> See RFC 4880, section 13.9 for more details on the mode of operation.
> btw, can someone explain to me what the design rationale for that
> "variant" is? I did not find an explanation in the RFC as to *why* the
> design choices were made in that particular way.

Short answer, it's historical.  There has just never been a strong
reason to change it.


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