Hi, Recently, I've been looking into securing email at the MTA level, and would like to get your thoughts on implementation possibilities and related issues. The problems that I'm trying to solve are: 1. Host authentication 2. Data privacy In order for the widespread encryption to work, several things need to occur: 1. Phase-in of the new stuff 2. Backward compatibility (ability to continue to work in the clear) for a period of years 3. A single worldwide mechanism, defined by an RFC, and freely available, except, perhaps, in the case of commercial MTAs. (i.e., the use of RSA seems appropriate for host and session key management, and is free via RSAREF in the US, free outside of the US, but not free for commercial use. This seems acceptable to me.) Two types of approaches are possible: 1. Adding to the SMTP protocol itself, allowing for MTAs to identify crypto-capable peers, and then performing authentication and session encryption where possible. 2. Waiting for a cryptographic transport layer network protocol (such as what is being proposed in draft-ietf-tls-ssh-00), allowing SMTP to remain untouched, and only requiring MTAs to add support for the new network protocol. I like the second approach better, because it allows more problems to be solved with one move, and it would be easier to add crypto functionality to our common network utilities by simply making them aware of the new transport layer protocol. The first approach would require redefinitions of RFCs for each of the services, and lots of redundant work. I mentioned my interest in an SSH-capable MTA to Tatu Ylonen <ylo@ssh.fi>, and he as also expressed interest. The word from him on the status of the SSH Internet Draft is that a reference implementation should be available early next month. I'm considering using that reference implementation to add SSH capability to an MTA, perhaps sendmail. My questions are: 1. Which of the two approaches seems to make the most sense to you? 2. Is there another approach that could work better? 3. Is there interest in adding SSH functionality to sendmail in the near future (either by the draft spec, or once the RFC has been published)? Please feel free to pass this around, if you deem appropriate. I'm interested in lots of feedback before deciding if and how to go ahead with the project. Thanks. -- C Matthew Curtin MEGASOFT, LLC Director, Security Architecture I speak only for myself. Don't whine to anyone but me about anything I say. Hacker Security Firewall Crypto PGP Privacy Unix Perl Java Internet Intranet cmcurtin@research.megasoft.com http://research.megasoft.com/people/cmcurtin/