create .asc signatures with GPG
This command will make gpg read my.file and create a detached signature for
it called my.file.asc. So you can use it to sign pretty much any file. I'm
also explicitly specifying which key I'm using for signing. (1234...) Just in
case I don't want to use my default signing key here.
gpg --armor --default-key 1234... --detach-sign my.file
This here demonstrates how I'm verifying the signature with gpg. This command
assumes that my.file is located in the same directory as my.file.asc.
gpg --verify my.file.asc