Security

Two practical pillars for protecting data on the device: encrypted database and biometrics as an access gate.

Encrypted database (SQLite3MC)

Open SQLite with a key — ChaCha20-Poly1305 cipher by default (or SQLCIPHER):

byte[] chave = derivarChaveDaSenha(senhaUsuario);   // ⚠️ derive from password with a KDF — NEVER hardcode
try (SqliteDb db = SqliteDb.open("cofre.db", chave)) {
   // … data transparently encrypted …
   db.rekey(novaChave);                              // swaps the key (e.g. when the user changes the password)
}

• Zero cost without a key, transparent cipher with a key — without a key it’s plain SQLite; with a key, everything is encrypted/decrypted on access, without changing your SQL.
• Never hardcode the key. Derive it from a user password with a KDF; store only the necessary material in the platform keystore.
• Be careful when removing the cipher (rekey to unprotect) — the file becomes readable in the clear.

Biometrics as an access gate

Before a sensitive area (finance, personal data), require biometrics:

if (Biometry.isAvailable()) {
   Biometry.authenticate("Acessar cofre", "Cancelar", false,
      (res, msg) -> Component.onUI(() -> {
         if (res == Biometry.AuthResult.SUCCESS) abrirCofre();
         else loginPorSenha();                 // always a fallback
      }));
} else {
   loginPorSenha();
}

• Biometric data never leaves the device — the app only receives SUCCESS/FAILURE/etc.
• Biometrics is local authentication: it complements, it does not replace, the application’s authentication (server login).

Other precautions

• Clipboard: don’t copy secrets to the clipboard (Device.clipboardCopy) — it becomes accessible to other apps.
• Files/homeFolder: data in Device.homeFolder is not encrypted by default — use the encrypted database for anything sensitive.
• Logs: don’t log passwords/tokens with Debug.log.

Best practices

• Sensitive data → encrypted SQLite; key derived from a password (KDF), never in the code.
• Biometrics as a local gate + always an application-level fallback.
• No secrets in the clipboard, plaintext files, or logs.

Common mistakes

• Hardcoded key in the code (anyone can extract it from the binary).
• Treating biometrics as if it replaced the server login.
• Storing a token/password in an unencrypted file in homeFolder.

See also

• Persistence with SQLite · Biometrics