How do I encrypt plaintext with GnuPG?

email encryption plaintext gnupg
humble_coder picture humble_coder · Mar 31, 2011 · Viewed 36.2k times · Source

I've been working a great deal with GnuPG lately and have come to depend on its ability to encrypt files, etc.

However, I am currently working on a couple of projects that involve communication (i.e. chat,email, etc) where I'd like to use existing keys to encrypt/decrypt text itself as opposed to a "container" such as a file or disk image.

I suppose I could encrypt the container, convert the stream to base64 (or something appropriate) then mark the text as such, but I would guess there is a more straightforward solution. I'm sure there is something simple I'm missing, but, well, I'm missing it.

Any ideas?

Answer

David Wolever picture David Wolever · Mar 31, 2011

What about:

$ echo "hello" | gpg --symmetric --armor --passphrase "asdf"
-----BEGIN PGP MESSAGE-----
Version: GnuPG v1.4.11 (Darwin)

jA0EAwMCWfhRZo0AiwVgyRw5Q26Tf+i6OCiQOVoUNJZEfz5ekBJw6BdVpE88
=ecV3
-----END PGP MESSAGE-----

If this is what you're looking for, you'll want to setup gpg-agent to handle the passphrase… Passing it in from the command line like that is fairly insecure (as any program on the machine could steal it).

And if by “existing keys” you mean “existing pub/priv key pairs”, then:

$ echo "hello" | gpg --encrypt --armor -r B230230D
-----BEGIN PGP MESSAGE-----
Version: GnuPG v1.4.11 (Darwin)
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=SGgD
-----END PGP MESSAGE-----

In both cases, the message is decrypted using:

$ cat encrypted_message | gpg
gpg: CAST5 encrypted data
Enter passphrase: asdf
gpg: encrypted with 1 passphrase
hello

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