-----BEGIN PGP SIGNED MESSAGE-----
In
<3(_dot_)0(_dot_)3(_dot_)32(_dot_)19980601143058(_dot_)00a30ad0(_at_)mail(_dot_)pgp(_dot_)com>,
on 06/01/98
at 02:30 PM, Jon Callas <jon(_at_)pgp(_dot_)com> said:
The above deals with backwards compatibility without introducing need
to be non-compliant. It is just a re-wording effectively, but is more
correct I feel (unless I have misunderstood some implication).
We have to deal with this situation. Imagine that you're using a maximal
(supports everything) OpenPGP implementation, and you're sending a
message a minimal OpenPGP implementation (which is 3DES only) and a 2.6
implementation (which is IDEA only), then there's a conflict.
For handeling such situations I had though of modifying the PGP/MIME spces
to include a new MIME Type: encrypted/alternative.
Say we have a text message M and we need to encrypt it to 2 recipiants, 1
using IDEA (S1) and 1 using Cast5 (S2).
What we would do is create a multipart document where the 1st part would
contain S1(M) along with the P1(S1) P2(S1) and the second part would
contain S2(M) along with P1(S2) P2(S2).
This way 1 message can be encrypted to multiple recipiants with
confilicting/unknown symetric key capabilities.
While I am on this topic I would like to see the ability for parallel
signatures for handeling confilicting public key & hash algorithms
capabilities.
Say we have a text message M and the signer has both RSA (P1) & DSA (P2)
keys.
The signer would generate 2 hashes of the message, one MD5 (H1(M)) and one
SHA1 (H2(M)). He would then generate 2 signatures P1(H1(M)) and P2(H2(M))
and attach them to the bottom of the message as signature/parallel
attachments.
This seems even more important that the encrypted/alternative becaues
unlike encryption there is no way of knowing the capabilities of the
reader of a signed message.
I have outlined both of these in my PGP Integration Paper:
http://users.invweb.net/~whgiii/pgpemail_5.html
- --
- ---------------------------------------------------------------
William H. Geiger III http://users.invweb.net/~whgiii
Geiger Consulting Cooking With Warp 4.0
Author of E-Secure - PGP Front End for MR/2 Ice
PGP & MR/2 the only way for secure e-mail.
OS/2 PGP 5.0 at: http://users.invweb.net/~whgiii/pgp.html
- ---------------------------------------------------------------
Tag-O-Matic: Dogs crawl under gates, software crawls under Windows!
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Tag-O-Matic: OS/2: Your brain. Windows: Your brain on drugs.