A question on encryption

[Marcin Borkowski <mbork@wmi.amu.edu.pl>]

Hi all,

I'm experimenting with encryption in Emacs using the EPG library.  I'm
using Emacs version:

============================================================
GNU Emacs 24.3.1 (i686-pc-linux-gnu, GTK+ Version 3.4.2) of 2013-08-22 on chindi02, modified by Debian
============================================================

and gpg version:

============================================================
gpg (GnuPG) 1.4.14
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Home: ~/.gnupg
Supported algorithms:
Pubkey: RSA, RSA-E, RSA-S, ELG-E, DSA
Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH,
        CAMELLIA128, CAMELLIA192, CAMELLIA256
Hash: MD5, SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2
============================================================

I created a test file (call it "test") with a single line of text and
did two things:

1. C-x C-f test RET, C-x C-w test.gpg RET

Then I selected the key and hit ok.

2. From the command line:
gpg -e -r key-id -o test2.gpg test

The two resulting files were different (difference in length of 3
bytes; find-file-literally and manual inspection showed that the
beginnings were identical, but the endings were not).

My question is: why is that so?  I instrumented the function
epg-start-encrypt for Edebug, and it seems that the argument list it
constructed was identical or equivalent to the one I'm giving on the
command line.

My other question is: is it fine?  I'm an (almost) complete layman
with crypto, and I don't want to open some huge security hole because
of my ignorance.  (I want to store my email passwords in encrypted
files, set a very short timeout in gpg-agent and connect it to my
mailing client, so that stealing my laptop won't enable the thief to
impersonate me.)

Best,

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Adam Mickiewicz University