1. User enters password → unlock secure key. 2. Server sends random nonce. 3. Client signs nonce with DK (Ed25519). 4. Server verifies signature with public key registered during enrollment. | Threat | Mitigation | |--------|-------------| | Keylogger captures password | Secure key seed required; password alone insufficient | | Phishing site | Token bound to origin (WebAuthn-like binding) | | Server database leak | Only public key or seed verifier stored, not seed | | Replay attack | Time window or nonce freshness | | Lost secure key | Recovery mnemonic (offline, high entropy) | 5. User Interface Design (Example) Setup screen:

[🔐 Digital Secure Key Password Setup] Create a strong master password: [ ] Confirm password: [ ]

"client_nonce": "base64...", "signature": "base64..."

✅ Secure key created.

secure_key_seed = secrets.token_bytes(32) encrypted_seed = xor_bytes(secure_key_seed, password_key) # simplified

Digital Secure Key Password Login Master password: [************]