On Wed, 18 Mar 1998, Hal Finney wrote:
Is the plaintext put through the cfb system, i.e. xored with the iv?
(I assume I would discard any key material, but not the iv).
Or is it intended to be completely unencrypted?
I don't follow you here. In CFB mode, the ciphertext is fed back through
the cipher (Blowfish in this case), and the result of that is xored with
the plaintext to produce the next block of ciphertext.
You misunderstand my question.
Type 0 is indicated as a "plaintext" conventional algorithm. But is says
nothing about the rest of the CFB and key stuff which applies to every
other cipher type.
It can mean one of the following, or even something else:
1. Although there is a PGP PK header, the data where the conventional
encryption packet should be will not be a conventional encryption packet,
but a literal, or other unencrypted plain text.
2. There is a conventional encryption packet, but no IV is present (i.e.
the first 10 bytes for the reset), and it merely encapsulates literal data
which requires no further processing. Or the 10 bytes are present and
ignored, with the plaintext data starting after the cfbreset.
3. Everything is handled like every other cipher, with a 10 byte iv prefix
(last byte pair as a check), with a reset, and using the IV to XOR things,
the only difference is where the CAST, IDEA, 3DES, etc. transform is,
nothing happens. The key material is provided for the other ciphers is
not used in any way.
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