Re: knowledge and belief

["Mark E. Shoulson" <shoulson@CS.COLUMBIA.EDU>]

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>Date:         Thu, 8 Jan 1998 19:16:23 -0300
>From: "=?iso-8859-1?Q?Jorge_J._Llamb=EDas?=" <jorge@INTERMEDIA.COM.AR>
>
>But I still don't understand the game (is it a game?). What does
>PGP stand for? What is the objective? Is there a winner (the one
>who first guesses which key belongs to each participant?) Or is
>it a cooperative effort, everyone wins when all the keys found
>their owner? How can the first person to sign a key tell who the
>key belongs to?

Woops, sorry.  PGP is a system for encrypting data, using public key
cryptography.  If you know my public key (it's kept in public repositories,
or I can mail it to you, etc), you can send me email that only I can read
(apart from cracking, etc, which is computationally infeasible, or assorted
carelessness on my part or whatever).  The public nature of my key doesn't
compromise the data you send though; only the *private* key (which I alone
have, hopefully) can decrypt stuff encrypted with the public key.  So it's
important to know that "my" key is really mine and not someone else
pretending to be me, or the pretender will be able to read it, not me.

Similarly, you could, with my public key, verify that it was I (or someone
who had access to my private key and passphrase, which should be nobody)
who wrote this letter, and nobody else.

~mark

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