SSH and Telnet [was Re: [Ma-linux] Two Sun Announcements]
Johnson, Steve (NIH/OD/ORS) [E]
johnsons at vrp.ncrr.nih.gov
Wed Feb 14 10:47:32 EST 2007
> not understand the complexities of the software they're using,
The cryptographic protocols have at their center a one-way function. Ex. multiply 2 large primes. Almost impossible to factor this number (and there is an exception for the Carmichael numbers). Another way to think of the one-way function is as a shattered plate; easy to break, tedious to put back together. In addition to this one-way function there is the question of who has the keys, the key swapping that occurs and that logically results in "public key" protocols. And note that the word KEY can be taken concretely, that is a key opens a lock.** With SSH the complexity will be the result of wrapping or bundling the central one-way key exchange with stuff like a salt, a nonce, timestamp, session-unique random number, aucilliary keys, etc. This wrapping just takes the result of the one-way function, and iterates, ie. run the one-way again using as input to the function the original result + the random number or timestamp that defines the session, and so on. Could wrap them both at the same time, or sequentially as steps in a handshake. The message blocks that get exchanged are wrapped like an onion, ie. layered.
> though, it does come down to the users
Here the logic is based on how well user applications and accounts are sandboxed, that is Role Based security. I note that Ferraiolo is out in a second edition, so I'll have to get that and review again his algebra that proves the air-tight security of RBS, and then see if I can hook this up with SELinux, a role-based security system. An easy example of a well sandboxed application is the browser. As far as your disk is concerned it is read-only other than cookies. Its life on the network port is more active.
**both terms, key and lock should be taken concretely and identified as locatable (whose box, what files, which application/libraries). An emphasis on taking things concretely is called reification though any comments on this are welcome.
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