OpenPGPEmailSummit: EmailValidation

Workshop at 2nd OpenPGP Email Summit, Dec 2015 run by Nicolai Josuttis

With this approach we want to establish a quick backward compatible solution to validate email addresses of UIDs of OpenPGP keys.

This would help to solve two major problems we have:

• People can currently easily upload faked keys (and they do)
• We have a lot of "moldered" keys (old keys not for any usage anymore

The key approach is:

• Define a standard signature format to signal successfull email validation
  • The standard format would be:
    • expires after 1 year
    • having a "signature notation" defining when/how/what was validated as JSON value
  • The standard format allows email clients to process them accordingly
    • E.g.: List who validated the email address or prefer validated email addresses over those not validated.
  • But even existing email clients can benefit from them:
    • According to the WebOfTrust a user can grant trust (and therefore priority) to emails with specific signatures

• Establish some initial validation servers to perform that validations on request
  • Request might be explicit or implicit triggered when uploading own key
  • Sends email to UID encrypted with the key to ensure that the one who confirms has the private key
  • Validation can be done asynchonously (not hindering immediate use of a new key)

Key properties of the approach are:

• No change of existing key server infrastructure or protocol
• Existing email clients can use it

• Yes, this is a CA-like approach
• Careful selection of initial CAs
  • Options: Current SMime CAs, trusted organizations, CCC, ... ?
• Fast establishment possible when e.g. enigmail and PGPTolls support it in new version
• The standard format might also be used by email providers, who provide both email address and keys (e.g. Google)

• This is *no perfect solution* but it makes faking keys a lot harder and easier to detect
  • Solution against trolls not against secret services

Open issues:

• How to ensure that the validation request is triggered by the owner of the key?
  • To avoid spam DOS
  • Answer: explicit request by email client that supports this approach or by user sending a specific email.

Initial Proposal: https://lists.gnupg.org/pipermail/gnupg-users/2015-July/053971.html

Slides: attachment:EmailValidation20151207.pdf

Whiteboard 2nd OpenPGP Summit: attachment:Whiteboard_EmailValidation.png