🚀[Feature]: Deterministic Key Generation

[MariusStorhaug]

Overview

Enhance the current Sodium module by adding deterministic key generation via a string-based seed. This enables seamless, non-interactive file encryption/decryption for users and improves clarity in API usage.

Why

• Seamless User Experience:
  Users can encrypt and decrypt files automatically without needing to remember or input passwords. A consistent key is generated from a user-defined seed.

• Deterministic Key Pair:
  Using a seed ensures that the same key pair is produced every time for a given seed, enabling reliable, repeatable encryption/decryption operations.

What

• Extend Key Pair Generation:
  • Add an optional -Seed parameter to New-SodiumKeyPair.
  • When provided, derive a 32-byte seed (e.g., via SHA-256) from the input string.
  • Use the derived seed with LibSodium’s crypto_box_seed_keypair to generate a deterministic key pair.
  • Retain the existing random key generation if no seed is provided.

How

1. Deterministic Key Generation:

   • In PowerShell:
     Check for the -Seed parameter in New-SodiumKeyPair.
     If provided, convert the seed string to bytes and compute a SHA-256 hash to produce a 32-byte value.
   • In C# Binding:
     Add a DllImport for crypto_box_seed_keypair:

     [DllImport("libsodium", CallingConvention = CallingConvention.Cdecl)]
     public static extern int crypto_box_seed_keypair(byte[] pk, byte[] sk, byte[] seed);

   • Call:
     Use crypto_box_seed_keypair when a seed is provided, otherwise fall back to crypto_box_keypair.

2. Cross-Platform & Backward Compatibility:

   • Ensure that the changes work seamlessly on Windows, Linux, and macOS (using PowerShell 7.4 with .NET 8.0).
   • Maintain existing behavior for users who do not supply a seed.