Size of encrypted files
Tue Mar 4 15:39:01 2003
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On Tue, Mar 04, 2003 at 02:51:59PM +0100, Preben Mikael Bohn wrote:
> Dear all, I'm trying to use gpg to encrypt files using only symmetric ciphers.
> I'm using the following:
> gpg --symmetric --batch --no-tty -z 0 --cipher-algo 3DES --passphrase-fd 0
> plain.txt < passwd.txt
> Can anyone explain the following:
> 1) How is passwd.txt being used in the encryption algorithms when used as the
> above (as the key directly, padded with something, stripped off the 8'th bit,
By default, it is mangled as specified in RFC-2440, section 3.6.
Basically, it is salted and then hashed multiple times.
As the key directly.
> 2) How come the encrypted file size is significantly larger than the plain
> file? I would have expected it to be only slightly larger due to padding of
> the plain-text.
- --symmetric doesn't do a straight encryption of plaintext into
ciphertext. There are headers, a session key (yes, even for symmetric
encryption), and so on.
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