android/docs/CRYPTO_GUIDELINES.md

Crypto Wallet Review Guidelines

Consumed by automated code review (CodeRabbit) and by human reviewers.

1. Secret material

Secret material = mnemonic phrases, BIP-39 seeds, private keys, extended private keys, signing keys, passphrases, PINs.

• MUST NOT appear in logs, analytics, crash reports, telemetry.
• MUST NOT be written to clipboard automatically or from background business logic.
• Clipboard copy is allowed only as an explicit user action from a sensitive-data screen, ideally with a confirmation step and routed through the app's centralized clipboard helper.
• MUST NOT be persisted in SharedPreferences, DataStore, or plain files.
• Acceptable storage only:
  • Android: Android Keystore (KeyStore.getInstance("AndroidKeyStore")).

2. Randomness

Cryptographic randomness MUST use:

• Android: java.security.SecureRandom.

kotlin.random.Random and java.util.Random are prohibited in any code path deriving nonces, salts, IVs, or private keys.

3. Android architecture

• Cryptographic work on Dispatchers.IO or a dedicated executor, never Dispatchers.Main.
• StateFlow / SharedFlow exposed to UI must not carry secret material.
• Log calls in crypto modules must be guarded by BuildConfig.DEBUG.