cryptography-handling-skill

name	Cryptography Handling Skill
description	Instructions for securely encrypting and decrypting data.

Cryptography Handling Skill

This skill defines how to handle encryption for the AxKeyStore before data is sent to GitHub.

Philosophy

The cloud (GitHub) is untrusted. All data must be encrypted at rest (locally before upload) and in transit (via HTTPS).

Implementation Details

Master Password

• The user must provide a master password or passphrase to unlock the keystore.
• Key Derivation: Use Argon2id or PBKDF2 to derive a symmetric encryption key from the user's password + salt.

Encryption Schema

• Algorithm: XChaCha20-Poly1305 or AES-256-GCM.
• Library: Use the age crate (for file encryption) or ring/sodiumoxide for low-level primitives.
• Structure:

  {
    "salt": "random_salt_for_kdf",
    "nonce": "random_nonce",
    "ciphertext": "base64_encoded_encrypted_data"
  }
  

Decryption Flow

1. Read the JSON blob from GitHub.
2. Extract salt, nonce, and ciphertext.
3. Prompt user for Master Password.
4. Derive Key using Salt + Password.
5. Decrypt ciphertext using Key + Nonce.

Dependencies

• argon2 (for KDF)
• chacha20poly1305 or aes-gcm (for encryption)
• rand (for generating salt/nonce)