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[Cfrg] Word-lists for Diffie-Hellman and Fingerprints

Aaron Zauner <azet@azet.org> Thu, 24 August 2017 17:32 UTC

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From: Aaron Zauner <azet@azet.org>
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Date: Thu, 24 Aug 2017 19:32:10 +0200
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Cc: Daniel Kahn Gillmor <dkg@fifthhorseman.net>, Werner Koch <wk@gnupg.org>, prz@acm.org, Moxie Marlinspike <moxie@thoughtcrime.org>
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Subject: [Cfrg] Word-lists for Diffie-Hellman and Fingerprints
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Hi,

A recent Twitter discussion [0] prompted me to look up any IETF documents specifying "PGP word lists" [1] as in use for for short authentication strings (SAS) in ZRTP and e.g. Signal. Apparently there's no such document, nor any other document that concerns word-lists that humans can easily read, say and hear/comprehend. GPG implements the ICAO phonetic alphabet as a command line option (`--with-icao-spelling`). This is nice, but I'd rather have a key-signing party that sounds like drunk anthropologists than forward air controllers having fun.  I've considered a patch. As the OpenPGP WG has been "closed", I'm unsure where to take this topic to, but CFRG seems to be a good place to ask.

The original publication - as used in PGPfone - is here: http://www.mathcs.duq.edu/~juola/papers.d/icslp96.pdf

..obviously there may be different views on how such a word-list should look like and I'm seeking input from the crypto and UX community. I think a standard or BCP would be nice to have. Obviously word-lists are in use for DH without WebPKI already - even different ones, as far as I know - but it would make sense to have a discussion on the topic.

What's your opinion on the matter?

Aaron

[0] https://twitter.com/AaronToponce/status/900767850142380033
[1] https://en.wikipedia.org/wiki/PGP_word_list

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