On 03/02/2023 18:37, Folderol wrote:
> What I'm after is a *desktop* program that will read a *specific* file and on
> being given the correct password will decript it, passing it direct to a text
> editor like kwrite, or better still a text reader that has no write capability.
>
> The person who this is intended for will not need to do any of the encryption.
>
> Any ideas?
>
I use GPG

=== You ===

1 Generate a passphrase. I use a (sufficient) number of bytes from
/dev/random piped into uuencode or base64. Save this in a file
(passphrase.txt), and send it to the counterparty.

2 . Encrypt the file

gpg --output "some file name" --batch --passphrase-fd 0 \
-r "receipient's email address" -e "input file name" \
< passphrase.txt

3. Export the generated public key

gpg --export -a "recipient's email address" > public.key

Send the public key to the counterparty - separately from the passphrase

4. Send the encrypted file to the counterparty - separately from the
other two items.

=== Counterparty ===

5. Save and import public.key

gpg --import public.key

6. Decrypt the file using the received file. the saved passphrase and
the imported public key

gpg --decrypt --output "some file name" --batch \
--passphrase-fd 0 -r "recipient's email address" \
"received data file" < passphrase.txt

If you have more files to send then only steps 2,4 and 6 are needed.

The "recipient's email address" is used as an identifier to distinguish
between vaious key pairs that you might have.