Re: [Evolution] Evolution/GPG



Thanks a lot! I need some time to let all this sink in. After all, last
year I didn't even know what GPG/PGP, GNOME, Linux, terminal or GNU are!
I'm only trying to get my Evolution to work perfectly. I've never heard
of that gpg command before or how it works. 

Thanks again!
SRW

fr. den 05. 02. 2016 klokka 12.39 (+0000) skreiv Pete Biggs:
OK.  The text of the message is not encrypted with a users key; the
text of the message is encrypted using a symmetric key - the key for
*that* method (the session key) is encrypted using public keys, and,
the important bit, there can be multiple public key encryptions in one
message. So for a command line example you can encrypt a file using 

   gpg -r ID1 -r ID2 -r ID3 -e 

Where one of those IDs is your own - hence you will be able to decrypt
the file because you will be able to decrypt the session key.

P.

Ah, I think I'm beginning to understand. So this is another form of
encryption, still using the receiver's public key, and s/he still has to
use his or her private key to decrypt the message? 

No, it's the same form of encryption that has always been used by
PGP/GPG, that's how it has always worked. Encrypting a large file with
a large key is hard work, so the file is encrypted with a small, throw
away, symmetric key - usually a 256-bit key these days.  That session
key is then encrypted using the intended recipient's public key and
placed at the beginning of the file. Have you never wondered why a tiny
file produces such a large encrypted file - if it were purely encrypted
with the recipient's public key, then a single character file would be
encrypted to a single character. Instead a single character file goes
to a 330-ish character encryption (depending on the size of the keys) -
it's all the overhead of session key encryption. Add another user to
the encryption and the file will expand again.

To see what's going on run gpg with the '-vvvv' option.  That will also
tell you if the files you are sending out are encrypted to the people
you intended.

P.
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