--list-only and symmetric encryption (fwd)

Atom 'Smasher' atom at suspicious.org
Tue Jul 6 17:31:17 CEST 2004

On Wed, 30 Jun 2004, Timo Schulz wrote:
> On Tue Jun 29 2004; 23:46, Atom 'Smasher' wrote:
> > key. i don't understand how a message can be efficiently ("efficiently",
> > meaning that the message is only encrypted once) encrypted to multiple
> > symmetric keys.
> That's not difficult, but I've to admit you need to know the OpenPGP
> format in detail to see it without thinking too much.
> Tag 3 "Symmetric-Key Encrypted Session Key Packets" has an optional
> field to hold the encrypted session key. This key is used to encrypt
> the message. The session key itself is encrypted via the S2K key
> derrived from a passphrase. If you have more passphrases, the same
> session key is encrypted with different passphrases (S2Ks).
> Tag3 (- Optionally, the encrypted session key itself, which is decrypted
>         with the string-to-key object.)
> You see the key for the _message_ is always the same, while the key
> to protect the session key itself is different for each passphrase.
> If you know one passphrase, you can decipher the message.
> Hope my achievement is clear to you.

so, if i understand this correctly, the message is still encrypted with a
random session key; multiple packets can each encrypt that session key to
a different symmetric key; any of those symmetric keys can be used to
decrypt the message. that's it? sounds cool....


 PGP key - http://atom.smasher.org/pgp.txt
 762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808

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