What these people ought to be doing is using the PGP messages only to transmit authentication data. eg: "When I talk today, I'm going to mention the Yankess". That way if a criminal cracks their system and reads plaintext copies of their email, they can't decrypt stored traffic. What they propose destroys the Perfect Forward Secrecy property of SF. SF also should display part of the parameters used to generate the ephemeral key, allowing the users to assure themselves that there is no Man In The Middle attack underway. (yes, this is obvious to most cpunk subscribers, but apparently not to all SF users) Peter Trei

---------- From: Major Variola (ret)[SMTP:mv@cdc.gov] Sent: Saturday, June 08, 2002 10:16 AM To: cypherpunks@lne.com; btmoore@iname.com; speak-freely@fourmilab.ch; ed@kapitein.net Subject: RE: PGP and Speak Freely (fwd)

[stuff y'all knew but for the record]

Basically the authors of the below post find that Speak Freely's reliance on out-of-band symmetric key exchange is solved with PGP email.

PGPfone does this for you over the same channel --using the mathemiracle of public-key crypto. Since you're both necessarily online, it can and does use Diffie-Hellman instead of RSA. It does not save the negotiated key pair so if no endpoint is taping, the conversation is lost to the wind.

Speak Freely is a nice piece of work, however compared to PGPfone it 1. requires OOB key exchange 2. isn't supported on Macs FWIW. I don't recall if SF works both ways, but PGPfone supports both IP and direct modem to modem links.

(Just for completeness, anyone researching the field should evaluate Nautilus too.)

At 12:25 PM 6/8/02 +0200, Eugen Leitl wrote:

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Date: Sat, 08 Jun 2002 03:42:12 -0500 From: "Benjamin T. Moore, Jr." <btmoore@iname.com> To: ed@kapitein.net, speak-freely@fourmilab.ch Subject: RE: PGP and Speak Freely

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Ok, let me see if I can maybe clarify what the issue is... Speak Freely

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offers the ability to encrypt your voice conversations in real time. If you have the "Crypto capable" version, when you've made a connection to someone, you both can enter an agreed upon key and your conversation will be secure from that point forward. This of course creates several problems. If someone is listening in, monitoring your conversation/traffic or packet sniffing, if for instance, you were to say in the conversation, lets use the word "monkey" for an IDEA key and you both typed in the word "monkey," your conversation would be encrypted using "monkey" as an IDEA key. The

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problem of course is, if someone is monitoring your conversation, they'd of heard you agree upon a key and they'd simply enter in the same key and continue to monitor.

Thus, you need a method of securely exchanging either an agreed upon key or a generated key - Speak Freely will generate keys that you may copy and

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paste into any of the various windows for the various encryption algorithms. PGP, Pretty Good Privacy, is one damn good method of securely exchanging those keys. You may of course e-mail the key in an encrypted

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e-mail or file to the intended recipients or you could even send the encrypted file using several of the Instant Messaging Clients with a file transfer protocol. These methods will certainly work very well. However, take this example which happened to me just last evening. A friend and I were needing to set up a secure conversation. After we couldn't get Speak Freely to handle the key exchange, we decided to e-mail the key in a PGP encrypted e-mail. Trouble was, the mail server was down on his ISP. He could neither receive or send mail. If he hadn't had an auxiliary web-based e-mail account, things might have been more complex than they were.

If Speak Freely were functioning correctly... let me amend that, IF we KNEW how to make Speak Freely handle the key exchange as described in the help file... It would have been a simple matter for us to allow Speak Freely to handle the key exchange. What is supposed to happen is... in the "connection" tab, you should be able to type the key identifier for the

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person(s), Speak Freely will then launch PGP - which it does - encrypt the generated key and transmit it to the intended recipients. This would automate secure communications.