How do I see what algorithm is used for a signature

Robert J. Hansen rjh at
Thu Oct 9 08:20:37 CEST 2014

On 10/9/2014 12:54 AM, Doug Barton wrote:
> I'm sure there is a way to determine what algorithm a signature was 
> created with...

gpg2 --fixed-list-mode --with-colons --list-key [keyID]

Once you learn how to read that output, you get a *ton* of information.
 It's kind of overkill for most tasks, but it's kind of like learning
how to use flex and bison: once you get the knowledge, you wind up using
it in places you never thought you would before.

Look for lines that look roughly like:


The number in the fourth field (third, if you're zero-indexing), which
here is 17, is the algorithm descriptor.

1: RSA (encrypt or sign)
2: RSA (encrypt-only -- if you see a sig with this, something's wrong)
3: RSA (sign-only)
16: Elgamal (encrypt-only -- ditto)
17: DSA
19: Reserved for ECDSA

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