feat: (core) Passphrase binding and recovery

[coodos]

Summary

Enable eVault recovery using eName and passphrase, while preventing brute force. Hash must never be readable and comparison must be rate-limited per IP with exponential backoff.

Requirements

• Store only hash(passphrase) in Protected Zone.
• Protected Zone exposes a compare function:
  • input: eName, passphrase candidate, source IP
  • output: match boolean, backoffSeconds on failure
• Rate limit and exponential backoff are IP-specific.

Recovery compare flow

sequenceDiagram
 actor User
 participant App
 participant Vault as eVault Protected Zone

 User ->> App: Recover (eName, passphrase)
 App ->> Vault: ComparePassphrase(eName, candidate, ip)

 alt Match
 Vault -->> App: success + recoveryToken
 App -->> User: Recovery success
 else Mismatch
 Vault -->> App: failure + backoffSeconds
 App -->> User: Retry after backoff
 end

Loading

IP backoff policy

flowchart TD
 A[Attempt from IP] --> B{Passphrase match?}
 B -->|Yes| C[Return success]
 B -->|No| D[Increment failure counter for IP]
 D --> E[Compute backoffSeconds = base * 2^failures]
 E --> F[Enforce cooldown for IP]
 F --> G[Return failure + backoffSeconds]

Loading

Acceptance criteria

• Passphrase hash is stored only in Protected Zone and is non-readable.
• eVault exposes a recovery compare endpoint/function.
• Compare operation is IP rate-limited.
• Exponential backoff is enforced per IP on consecutive failures.
• Response includes backoffSeconds (or equivalent) on mismatch.
• System does not allow extraction of stored hash or comparison oracle beyond rate-limited interface.