git-crypt enables transparent encryption and decryption of files in a git repository. Files which you choose to protect are encrypted when committed, and decrypted when checked out. git-crypt lets you freely share a repository containing a mix of public and private content. git-crypt gracefully degrades, so developers without the secret key can still clone and commit to a repository with encrypted files. This lets you store your secret material (such as keys or passwords) in the same repository as your code, without requiring you to lock down your entire repository.
git-crypt was written by Andrew Ayer . For more information, see https://www.agwa.name/projects/git-crypt.
See the INSTALL.md file.
Generate a secret key:
git-crypt keygen /path/to/keyfile
Configure a repository to use encryption:
cd repo
git-crypt init /path/to/keyfile
Specify files to encrypt by creating a .gitattributes file:
secretfile filter=git-crypt diff=git-crypt
*.key filter=git-crypt diff=git-crypt
Like a .gitignore file, it can match wildcards and should be checked into the repository. Make sure you don't accidentally encrypt the .gitattributes file itself!
Cloning a repository with encrypted files:
git clone /path/to/repo
cd repo
git-crypt init /path/to/keyfile
That's all you need to do - after running git-crypt init, you can use
git normally - encryption and decryption happen transparently.
The latest version of git-crypt is 0.3, released on 2013-04-05. git-crypt aims to be bug-free and reliable, meaning it shouldn't crash, malfunction, or expose your confidential data. However, it has not yet reached maturity, meaning it is not as documented, featureful, or easy-to-use as it should be. Additionally, there may be backwards-incompatible changes introduced before version 1.0.
Development on git-crypt is currently focused on improving the user experience, especially around setting up repositories. There are also plans to add additional key management schemes, such as passphrase-derived keys and keys encrypted with PGP.
git-crypt is more secure that other transparent git encryption systems. git-crypt encrypts files using AES-256 in CTR mode with a synthetic IV derived from the SHA-1 HMAC of the file. This is provably semantically secure under deterministic chosen-plaintext attack. That means that although the encryption is deterministic (which is required so git can distinguish when a file has and hasn't changed), it leaks no information beyond whether two files are identical or not. Other proposals for transparent git encryption use ECB or CBC with a fixed IV. These systems are not semantically secure and leak information.
The AES key is stored unencrypted on disk. The user is responsible for protecting it and ensuring it's safely distributed only to authorized people. A future version of git-crypt may support encrypting the key with a passphrase.
git-crypt is not designed to encrypt an entire repository. Not only does that defeat the aim of git-crypt, which is the ability to selectively encrypt files and share the repository with less-trusted developers, there are probably better, more efficient ways to encrypt an entire repository, such as by storing it on an encrypted filesystem. Also note that git-crypt is somewhat of an abuse of git's smudge, clean, and textconv features. Junio Hamano, git's maintainer, has said not to do this, though his main objection ("making a pair of similar 'smudged' contents totally dissimilar in their 'clean' counterparts.") does not apply here since git-crypt uses deterministic encryption.
git-crypt does not itself provide any authentication. It assumes that either the master copy of your repository is stored securely, or that you are using git's existing facilities to ensure integrity (signed tags, remembering commit hashes, etc.).
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