PGP reveals the key ID of the recipient of encrypted msg

Mark M. markm at voicenet.com
Mon Mar 11 23:50:08 PST 1996


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On Mon, 11 Mar 1996 savron at world-net.sct.fr wrote:

> I began testing PGP  a few days ago ( I'm a PGP newbie ) and I found 
> that it gives out the key ID of an encrypted message . From this you 
> can get the  identification of the recipient of the message , if it's 
> someone who has publicaly  distributed his  key (keyserver , homepage 
> ...) . So even if you are unable to decode the message you  can find 
> who is the recipient of a given message . I think this is a big 
> privacy problem .

The recipient of the message is right in the "To:" header of the message.
If you anonymously remail a message, however, only the last remailer in the
chain will know to whom the message is encrypted, but the last remailer can
also just read the "To:" header.  I don't find this to be a problem at all.

> 
> The problem is carried along when you encrypt a message for multiple  
> recipients , you get the key IDs of all the recipients and same 
> problem as above .  I think something like 'blind email copy' should 
> be used , because the recipients don't have to know the identity of 
> each other .

You could just encrypt a message to different key ID's seperately, rather than
in one pass of PGP.  The would have the effect of Bcc.

- --Mark

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
markm at voicenet.com              | finger -l for PGP key 0xf9b22ba5
http://www.voicenet.com/~markm/ | bd24d08e3cbb53472054fa56002258d5
"The concept of normalcy is just a conspiracy of the majority" -me


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