Preparing To Migrate Off of SHA-1 In OpenPGP

jamie found a note on debian-administration.org, the first in a promised series on migrating off of SHA-1 in OpenPGP. "Last week at eurocrypt, a small group of researchers announced a fairly serious attack against the SHA-1 digest algorithm, which is used in many cryptosystems, including OpenPGP. The general consensus is that we should be 'moving in an orderly fashion toward the theater exits,' deprecating SHA-1 where possible with an eye toward abandoning it soon (one point of reference: US govt. federal agencies have been directed to cease all reliance on SHA-1 by the end of 2010, and this directive was issued before the latest results). ... So what can you do to help facilitate the move away from SHA-1? I'll outline three steps that current gpg users can do today, and then I'll walk through how to do each one..."

Comments

Stupid question, but... multiple hashes?

[tlhIngan]

Really stupid question (not a cryptographer), but is there anything wrong with using multiple hash algorithms (hopefully none derived from one another)? Surely breaking two or more hashes simultaneously would be far harder?

E.g., MD5 is broken. But what if we use both MD5 and SHA-1?

What about SSL certificates?

[200_success]

According to x509(1) and ca(1), OpenSSL supports md2, md5, sha1, and mdc2 as options for message digests for certificates. Since MD2 and MD5 are already broken, and SHA1 is now suspect, that leaves just the relatively obscure MDC-2.

Can someone give me a quick rundown?

[swordgeek]

It's been a while since I had to deal with PGP keys and the like, and things have multiplied since then. Is there a simple explanation for the status/compatability/equivalency of...

pgp
openpgp
gpg
gnupg

And any others I'm missing?