Hi, Aryaga
In fact I run a quick test. I don't see that verbose command is showing which type of the cipher is used during decryption process at all (no matter if encryption is symmetric or public-key encryption) This is only showing while encrypting
Have a look:
1. Generate a key
C:\Program Files (x86)\PGP Corporation\PGP Command Line>pgp --gen-key "testciphter testcipher@ag.dom" --key-type rsa --encryption-bits 2048 --passphrase "plokij5%"
2. List key
C:\Program Files (x86)\PGP Corporation\PGP Command Line>pgp --list-keys
Alg Type Size/Type Flags Key ID User ID
----- ---- --------- ------- ---------- -------
RSA4 pair 2048/2048 [VI---] 0x1A78013D user3 <user3@ag.dom>
*RSA4 pair 2048/2048 [VI---] 0x82A87174 testciphter testcipher@ag.dom
2 keys found
3. Set preferred cipher (3des priority/order 1, aes192 priority/order 2)
C:\Program Files (x86)\PGP Corporation\PGP Command Line>pgp --set-preferred-ciphers 0x82A87174 --passphrase "plokij5%" --3des 1 --aes192 2
0x82A87174:set preferred ciphers (0:preferred ciphers updated)
4. List key details for 0x82A87174
C:\Program Files (x86)\PGP Corporation\PGP Command Line>pgp --list-key-details 0x82A87174
Key Details: testciphter testcipher@ag.dom
Key ID: 0x82A87174 (0x1C1A607F82A87174)
Type: RSA (v4) key pair
Size: 2048
Validity: Complete
Trust: Implicit (Axiomatic)
Created: 2014-08-14
Expires: Never
Status: Active
Cipher: TripleDES
Cipher: AES-192
Hash: SHA-256
Hash: SHA-512
Compress: ZLIB
Photo: No
Revocable: Yes
....
....
....
5. Encrypt file with 3des (symmetric encryption)
C:\Program Files (x86)\PGP Corporation\PGP Command Line>pgp -c test_file.txt --s
ymmetric-passphrase "plokij5%" --cipher 3des -v
pgp:encrypt (3157:current local time 2014-08-14T15:59:31+02:00)
test_file.txt:encrypt (3048:data encrypted with cipher TripleDES)
Encoding test_file.txt... 100% (⸥昱猥)
Wiping file pgp-2568-0.tmp... 100%
pgp-2568-0.tmp:encrypt (0:file wiped successfully)
test_file.txt:encrypt (3083:could not create output file test_file.txt.pgp)
6. Changed preferred cipher order to --aes192 1 --3des 2 (reason becuse while decrypting I have not seen which cipher is used in fact with verbose command)
C:\Program Files (x86)\PGP Corporation\PGP Command Line>pgp --set-preferred-ciph
ers 0x82A87174 --passphrase "plokij5%" --aes192 1 --3des 2
0x82A87174:set preferred ciphers (0:preferred ciphers updated)
7. List key details again to check the cipher order
C:\Program Files (x86)\PGP Corporation\PGP Command Line>pgp --list-key-details 0
x82A87174
Key Details: testciphter testcipher@ag.dom
Key ID: 0x82A87174 (0x1C1A607F82A87174)
Type: RSA (v4) key pair
Size: 2048
Validity: Complete
Trust: Implicit (Axiomatic)
Created: 2014-08-14
Expires: Never
Status: Active
Cipher: AES-192
Cipher: TripleDES
Hash: SHA-256
Hash: SHA-512
Compress: ZLIB
Photo: No
Revocable: Yes
Token: No
Keyserver: Absent
Default: Yes
...
...
....
8. Decrypt the file (symetric decryption) no information at all about type of cipher.
C:\Program Files (x86)\PGP Corporation\PGP Command Line>pgp --decrypt test_file.
txt.pgp --symmetric-passphrase "plokij5%" --overwrite remove -v
pgp:decrypt (3157:current local time 2014-08-14T16:23:12+02:00)
Decoding file test_file.txt.pgp... 100% (甥猥)
test_file.txt.pgp:decrypt (0:output file test_file.txt)
So based on this test I can state that decryption is done via prefered aes192 cipher. I can alo set preferred cipher to only one cipher aes192 and run decryption which will work as well:
9. Change to only one cipher --aes192 1
C:\Program Files (x86)\PGP Corporation\PGP Command Line>pgp --set-preferred-ciph
ers 0x82A87174 --passphrase "plokij5%" --aes192 1
0x82A87174:set preferred ciphers (0:preferred ciphers updated)
10. List key - one cipher only:
C:\Program Files (x86)\PGP Corporation\PGP Command Line>pgp --list-key-details 0
x82A87174
Key Details: testciphter testcipher@ag.dom
Key ID: 0x82A87174 (0x1C1A607F82A87174)
Type: RSA (v4) key pair
Size: 2048
Validity: Complete
Trust: Implicit (Axiomatic)
Created: 2014-08-14
Expires: Never
Status: Active
Cipher: AES-192
Hash: SHA-256
Hash: SHA-512
Compress: ZLIB
Photo: No
Revocable: Yes
Token: No
Keyserver: Absent
Default: Yes
Wrapper: No
Prop Flags: Sign user IDs
....
....
...
11. Decrypt again
C:\Program Files (x86)\PGP Corporation\PGP Command Line>pgp --decrypt test_file.
txt.pgp --symmetric-passphrase "plokij5%" --overwrite remove --v
pgp:decrypt (3157:current local time 2014-08-14T16:42:38+02:00)
Decoding file test_file.txt.pgp... 100% (甥猥)
test_file.txt.pgp:decrypt (0:output file test_file.txt)
So looks like it is working but I don't see the way how to verify and force cipher 2 usage during decryption (unless I need to verify pgp command line syntax in more details )
HTH