Key Used to Lookup Symmetric Passphrase.

[Ralph Corderoy]

Hi,

I'm using gnupg 2.1.18-1 on Arch Linux.  `gpg -c foo' asks for a
passphrase.  I enter `p-foo' twice.  For file bar it's `p-bar'.  `gpg -d
foo.gpg' doesn't prompt, which is good, getting the passphrase from the
agent.  Ditto bar.gpg.  If I rename foo.gpg to xyzzy.gpg it still
doesn't prompt, finding the correct passphrase.  What's the key being
used to look up the symmetric passphrase?  Is it something random stored
in *.gpg and thus survives the rename?  How can I list these in the
manner of -k and -K?

Very happy to read documentation on it, but haven't spotted anything so
far.

Cheers, Ralph.