Key derivation

[chmac]

Ideally we'd be able to send a user a link to the repo including a short password and then they'd be able to download and decrypt the repo with that password.

It seems like argon2 is the current state of the art in key derivation. Here's the thinking:

• Add a plain text file to the encrypted repo which contains
  • The key derivation salt and other inputs
  • The key length, potentially for each key
  • Some kind of encryption "version" or algorithm information
    • This would allow for future upgrades of the protocols in use, etc

This would allow somebody knowing the password and having the repo contents to be able to decrypt, while still making the contents without the password impossible (currently computationally infeasible) to decrypt.

[chmac]

The goal of the first step of this issue is to add an argon2 implementation to the git-encrypted package, and create a function which takes the following inputs:

• the salt and other parameters (to be defined)
• a password provided by the user

This function should then compute a 96 byte secret key. This would be a successful first step towards achieving the bigger mission described in this ticket.

[chmac]

The salt is randomly generated once, and saved. For now, you could hardcode it in the TypeScript file.

[chmac]

Suggested steps to implement:

• Pick an argon2 npm package to use
  • Happy to discuss choices with you after you’ve done some research if you like
  • Bottom line though, if you want to pick one and move forward, do that, done today always beats perfect tomorrow
• Create a new file for the new function
• Create a stub function const foo = () => {}
• Add a test file like foo.test.ts
• Call your function in the test and provide some arguments

• .toMatchSnapshot() the result

• Start implementing your function

Two hard problems in computer science, cache invalidation and naming things!