privatize 👀

privatize enables partial encryption/decryption for the contents of a heredoc (<<PRIVATE).

When installed in a git repository, files you choose to protect will have the contents of the heredoc <<PRIVATE automatically encrypted on commit and decrypted on checkout while the rest of the file remains untouched.

Inspired by git-crypt.

🚨🚨🚨 NOTE: this is a WIP, use at your own peril!

Installation

MacOS

brew tap higgins/privatize
brew install privatize

Using with git

To configure a repository to use privatize:

cd yourRepo
privatize git-init

Specify files to partially encrypt/decrypt by creating a .gitattributes file:

someSecretFile filter=privatize diff=privatize
*.org filter=privatize diff=privatize
credentials/*.md filter=privatize diff=privatize

Copy your symmetric key to a secure place:

privatize export-git-key exampleKeyFilename.key

Unlock a newly cloned repo:

privatize git-unlock exampleKeyFilename.key

Once you've either privatize git-init or privatize git-unlock'd your repo and updated your .gitattributes file, use git as you normally would and your files will be transparently encrypted/decrytped.

Make sure your .gitattributes rules are in place before you add sensitive files, or those files won't be encrypted!

Using with pipes

# Create a stand-alone symmetric key for use outside of git
privatize create-key symmetric.key

# Encrypt a file and pipe to stdout
cat someFileToPartiallyEncrypt | privatize encrypt symmetric.key

# Decrypt a file and pipe to stdout
cat someFileToPartiallyDecrypt | privatize decrypt symmetric.key

Markup example

To privatize the contents of a file, make sure you wrap your text to be privatized with <<PRIVATE and PRIVATE. For now, both tags must start at the beginning of the line.

# example.txt

Today I a burrito. 🌯
<<PRIVATE
I was on the toilet for hours.
PRIVATE
I got a lot of reading done.

Once privatized becomes

# example.txt

Today I a burrito. 🌯
<<PRIVATE
xuJ0fld2vmNWaVLogTIufmWsiFso
PRIVATE
I got a lot of reading done.

Motivation

I keep a daily journal in an org-mode file shared publicly. I share it publicly because I like to hold myself accountable to that. I often describe parts of my life that for one reason or another should be kept private (significant details of my friends and family, ongoing status of to-be-launched projects, etc) and don't want to have to change contexts (files) to document those aspects.

Voilà.

Practical uses

Aside from how I use it, here are some other useful applications:

• Transparent legal documentation with PII redacted
• Privatizing content for paying customers
• Anywhere the concept of literate programming applies

Current status

This is a functioning prototype and I'm open to suggestions for improvements. Ping me or submit a pull-request!

Security

privatize's encryption scheme is shamelessly borrowed from git-crypt's. We encrypt the contents of heredocs using AES-256 in CTR mode with a synthetic IV derived from the blob's SHA-1 HMAC.

One rule holds true: Never share the private key with those you don't want reading your encrypted data, Frodo Baggins!

TODO

• Allow for arbitrary HEREDOC strings ("<<CREDENTIALS", "```")
• Allow HEREDOC to start and end mid-line
• warn if PRIVATE/ heredoc's end sentinel is not within the encrypted contents (https://news.ycombinator.com/reply?id=30704575&goto=item%3Fid%3D30703161%2330704575)
• don't commit release binaries
• be less dramatic (git reset --hard), and warn if dirty on unlocking the repo
• add license in repo
• more warnings if heredocs are malformed (<PRIVATE, <<PIRVATE, etc)