ietf-openpgp
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Re: New results against SHA-1

2009-05-04 18:14:00

On May 4, 2009, at 2:22 PM, Daniel Kahn Gillmor wrote:

On 05/04/2009 01:38 PM, Werner Koch wrote:
Using a number (2) and, say, a dot as a prefix would be a better choice. We use algorithnm numbers anyway and OpenPGP users are used tp spell a large row of hex digits; we would only confuse them with an S and an H..

ok, that works for me.  would the prefix be in hex or decimal?  for
example, would an SHA512 fingerprint look like
a. 3dd7a2cb8f9e51f2fc096e7022a8192099aa89e10c699e46223851cc36f406b1beb734d5a7da0d8ebc08cc37e30088300c7a9ae81ba7ab758047a89cfa191aff

or

10.3dd7a2cb8f9e51f2fc096e7022a8192099aa89e10c699e46223851cc36f406b1beb734d5a7da0d8ebc08cc37e30088300c7a9ae81ba7ab758047a89cfa191aff

Ugh.  that's horrifically long either way.  Is a base64 encoding worth
considering?  it would shave off a third of the length, but it seems
like it would introduce significant ambiguity (0 vs O, A vs a, etc)

I'm sure there is a study somewhere that says just how long of a string a human being can handle without getting lost, but even without such a study I can say that 512 bits is just too long for usability. If you think about it, the whole point of fingerprints is that they're a short way to refer to a key. If we make them too long, we're hurting the very thing that fingerprints were created for.

"3dd7a2cb8f9e51f2fc096e7022a8192099aa89e10c699e46223851cc36f406b1beb734d5a7da0d8ebc08cc37e30088300c7a9ae81ba7ab758047a89cfa191aff " is not exactly the kind of thing someone could print on a business card or read to a corespondent over the phone.

David

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