Mathias Jean Johansen

Encrypting Files With GPG and Vim

I do most of my writing in Vim whether it is programming or editing ordinary documents. The only two exceptions are journals and emails. For journals, I’ve been using Day One for quite an extensive amount of time now, but I’ve been considering to replace it with Vim. In order to replace Day One, I need a way to effortlessly encrypt and decrypt text files. In this post, I’ll show you how I’ve set up an environment that enables me to do so.

By default, Vim provides you with the ability to encrypt and decrypt files in a quite simple manner. You open a file with vim -x or the :X command, and then Vim prompts you for an encryption key. When you’ve entered the encryption key twice, you are able to edit the document. If you try to print the document with cat afterwards, you’ll see gibberish like VimCrypt~01!gd)�/�:�-(%), but if you open the file with Vim, the editor will prompt you for the key phrase, and after entering the correct encryption key you can read and edit the file. There is a caveat to this approach, however. According to the :X help page, Vim has not been tested for robustness, and we do not want swap files, the viminfo file or any other files for that matter to expose our file contents, so instead we are going to rely on GPG and autocommands.

What we need to include in our .vimrc is the following autocommand group:

augroup encrypted
  autocmd BufReadPre,FileReadPre *.gpg set viminfo=
  autocmd BufReadPre,FileReadPre *.gpg set noswapfile noundofile nobackup
  autocmd BufReadPost *.gpg :%!gpg --decrypt 2> /dev/null
  autocmd BufWritePre *.gpg :%!gpg -ae --default-recipient-self
  autocmd BufWritePost *.gpg u
augroup END

Essentially, we disable auto-saving the .viminfo file, and then we disable swap files, undo files and backup files. After the buffer is read, we decrypt it with GPG, so that we are able to read the content in Vim. Before we eventually save our file, we encrypt the entire file with the user ID of the default key as the recipient of our message, and finally after writing the file we undo the last action, so that the file is still readable to us.