Opportunistic Encryption

[Per Tunedal]

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At 02:00 2003-05-16 +0400, you wrote:
 >
 >An example may be the best description, so I've written a rough draft.
 >I've broken OpenPGP use into 3 levels of sophistication.  Each level
 >can be attacked at the user's own pace.
 >
 >
 >Level 1: Opportunistic Encryption
 >=--------------------------------
 >For this level, the user just generates a key.  After that, the e-mail
 >client software does the following:
 >
 >A) All outbound messages are signed. Mail is encrypted whenever the
 >   recipient's public key is available. (See my previous post for
 >   algorithms on key selection when multiple untrusted keys exist.)
 >
 >B) When a signed message with an attached key is received, we verify
 >   that the attached key matches the key used to sign the message.
 >   If so, the key is automatically added to the local keyring.
 >
 >C) If a received message is signed but not encrypted, any reply to
 >   the signature owner should have our public key automatically
 >   included as an attachment.
 >
 >Eavesdropping protection is achieved after one round trip and no user
 >interaction or keyservers are required!
 >
 > - Yenot

I would like to add automatic use of robot-CA:s to the scheme. It's a
simple way of tieing a key to an e-mail address:
- - the user just generates a key
- - the client sends it to a robot-CA
- - the robot CA signs the key, encrypts it with the same key and returns it
to all e-mail addresses used in the userid.
- - the encrypted message from the robot-CA is received, decrypted, the
signed key is imported to the keyring and sent to at least one keyserver.

The rest as you proposed.

Yours,
Per Tunedal

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