I am currently reviewing Go's OpenPGP implementation with a view of possibly implementing bzip2 support for it, as well as testing compatibility with GNUPG. This is a simple GIST that shows how to decrypt a symmetrically encrypted file using go.crypto/openpgp. It can be useful for testing go.crypto/openpgp compatibility with various symmetric ci…

decrypt-symmetric.go

package main

import (
	"code.google.com/p/go.crypto/openpgp"
	"errors"
	"io"
	"log"
	"os"
)

// An empty Keyring
type emptyKR struct {
}

func (kr emptyKR) KeysById(id uint64) []openpgp.Key {
	return nil
}

func (kr emptyKR) DecryptionKeys() []openpgp.Key {
	return nil
}

const passphrase = "eisae4Iid8Jac2ee"

func promptFunction(keys []openpgp.Key, symmetric bool) ([]byte, error) {
	if !symmetric {
		// We only support passhphrases for symmetrically
		// encrypted decryption keys
		return nil, errors.New("Decrypting private keys not supported")
	}

	return []byte(passphrase), nil
}

func main() {
	file, err := os.Open("message.txt.gpg")
	if err != nil {
		log.Fatalln(err)
	}

	md, err := openpgp.ReadMessage(file, emptyKR{}, promptFunction, nil)
	if err != nil {
		log.Fatalln(err)
	}

	_, err = io.Copy(os.Stdout, md.UnverifiedBody)
	if err != nil {
		log.Fatalln(err)
	}

	// Check that any authentication code for the message was
	// verified successfully
	if md.SignatureError != nil {
		log.Fatalln("Integrity Check FAILED:", md.SignatureError)
	}
}