I would like to be able to check which (inner) symmetric algorithm was used to encrypt a file with GPG using a public key.
Somewhere I've read this can be done with
--list-packets, so I tried
$ gpg --list-packets encrypted_file.asc gpg: encrypted with 256-Bit ECDH key, ID 0865135E90D1AF38, created 2020-03-20 "First Last <email@example.com>" # off=0 ctb=84 tag=1 hlen=2 plen=94 :pubkey enc packet: version 3, algo 18, keyid 0865135E90D1AF38 data: [263 bits] data: [392 bits] # off=96 ctb=d2 tag=18 hlen=3 plen=1965 new-ctb :encrypted data packet: length: 1965 mdc_method: 2 # off=118 ctb=a3 tag=8 hlen=1 plen=0 indeterminate :compressed packet: algo=1 # off=120 ctb=cb tag=11 hlen=2 plen=0 partial new-ctb :literal data packet: mode b (62), created 0, name="_CONSOLE", raw data: unknown length
I thought the symmetric encryption algorithm was encoded in
mdc_method, but whatever algorithm I use to encrypt, it always displays
2 there. So this doesn't seem to be the correct approach.
How can I find out the symmetric algorithm?