Password Recovery: Automated Access to Encrypted Messages

TL;DR

This guide shows you how to automatically give a user access to their encrypted messages if they forget their password. We’ll use a secure key recovery system with multi-factor authentication and automated decryption.

Solution Guide

1. Choose a Key Recovery Method: There are several options, each with trade-offs.
   • Trusted Contacts: The user designates 2-3 trusted people who can help recover the key.
   • Key Sharing (with caveats): Split the encryption key into parts and store them separately (e.g., using Shamir’s Secret Sharing). This is complex to implement securely.
   • Hardware Security Module (HSM): Store the key in a dedicated hardware device. This offers high security but requires additional hardware costs.

   For this guide, we’ll focus on Trusted Contacts as it’s relatively easy to implement and understand.

2. Implement Multi-Factor Authentication (MFA): Before any key recovery process begins, ensure the user has MFA enabled. This adds an extra layer of security.
   • Common MFA methods include: Time-based One-Time Passwords (TOTP) via apps like Google Authenticator or Authy; SMS codes (less secure); Email verification (also less secure).
   • Implement a robust account lockout policy to prevent brute-force attacks.
3. Key Encryption and Storage: Encrypt the user’s encryption key with another key, protected by MFA.

   # Example using OpenSSL (for demonstration only - adapt for your environment)

   openssl enc -aes-256-cbc -salt -in user_encryption_key.txt -out encrypted_user_key.enc -k "your_mfa_protected_password"

   Store the encrypted_user_key.enc securely (e.g., in a database with strong access controls).

4. Trusted Contact Registration: Allow users to register trusted contacts.
   • Collect contact details (email addresses, phone numbers).
   • Verify the contacts’ identities (e.g., via email confirmation or SMS verification).
   • Store contact information securely.
5. Password Recovery Workflow: This is the core of the automation.
   1. User Initiates Recovery: The user requests password recovery through your application.
   2. Identity Verification: Verify the user’s identity using MFA.
   3. Contact Trusted Contacts: Send a notification to the registered trusted contacts, explaining that the user has requested key recovery.
      • Include a unique, time-limited code for each contact.
      • Clearly state the risks involved and the importance of verifying the user’s identity before providing assistance.
   4. Contact Confirmation: Each trusted contact enters their verification code into your application.
      • Require a minimum number of confirmations (e.g., 2 out of 3) to proceed.
   5. Key Decryption and Access Restoration: Once enough contacts confirm, decrypt the user’s encryption key using the MFA-protected password.

      # Example decryption (adapt for your environment)

      openssl enc -d -aes-256-cbc -salt -in encrypted_user_key.enc -out decrypted_user_key.txt -k "your_mfa_protected_password"

      Allow the user to access their messages using the decrypted_user_key.txt.

   6. Key Reset: After successful recovery, force a password reset for the user’s account and regenerate the encryption key.
      • This prevents unauthorized access if any trusted contacts were compromised during the process.
6. Auditing and Logging: Implement comprehensive auditing and logging of all password recovery events.
   • Log user requests, contact notifications, confirmations, decryption attempts, and key resets.
   • Monitor logs for suspicious activity.
7. Security Considerations:
   • Protect MFA Secrets: Securely store and manage the passwords used to protect the encryption keys.
   • Rate Limiting: Implement rate limiting on password recovery requests to prevent abuse.
   • Regular Security Audits: Conduct regular security audits of your key recovery system.
   • Contact Verification: Ensure trusted contacts are genuinely trustworthy and aware of their responsibilities.