ietf-openpgp
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Re: private key CFB

2003-11-17 14:06:21

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> Isn't that too short for a 256-bit key?

Indeed, my post included a 128-bit key computation.  (I also
used MD5, rather than SHA1 as asked.)  Sorry about that.

For a 256-bit key, based on SHA1, I get:
    53.f2.fd.a7.69.7d.0b.a6.c0.ee.18.4f.89.db.1d.f8.
    14.6c.d4.ad.36.1b.8c.4e.63.13.ab.68.75.a7.ad.0b.

I also generated a 64k-sized file and tested with "sha1sum",
getting the same first 20 bytes.

>>Sadly, GnuPG (1.2.2)'s --show-session-key doesn't seem to work on
>>symmetrically encrypted packets, but it might be easy to tweak.
>
>
> That's not what show-session-key is for.  It's for, well, showing
> session keys ;)

I think you may have misread my comment as wanting to produce the
session key that protects a secret key, based on the original
context.
I did not. I was talking about a "conventionally encrypted" message,
using a Symmetrically Encrypted Data Packet.  If the S2K doesn't
include an (*optional*) encryption of the session key, then the S2K
computation result *is* the session key; I was simply trying to use
that feature to generate an S2K output to check mine.

I think that the intended purpose of GnuPG's session key feature is
equally applicable here.  If you disagree, I'd be happy to discuss it
in a GnuPG forum.  In any case, it's not an OpenPGP issue.

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