Secure Login & Data Decryption

TL;DR

This guide shows how to securely authenticate users and then decrypt their stored data *after* successful login. We’ll focus on using strong passwords, hashing, salting, and a robust encryption method like AES.

1. Password Storage (Authentication)

Never store passwords in plain text! Use a secure hashing algorithm with salts.

1. Choose a Strong Hashing Algorithm: bcrypt, Argon2, or scrypt are good choices. They’re designed to be slow and computationally expensive, making brute-force attacks harder.
2. Generate Salts: A salt is random data added to each password before hashing. This prevents rainbow table attacks. Each user needs a unique salt. Store the salt alongside the hashed password (not with the plain text password!).
3. Hashing Process: When a user registers, take their password, add their unique salt, and hash it using your chosen algorithm.

   # Example Python using bcrypt
   import bcrypt
   salt = bcrypt.gensalt()
   hashed_password = bcrypt.hashpw(password.encode('utf-8'), salt)
   

4. Verification: When a user logs in, take their entered password, retrieve the stored salt for that user, hash the entered password *with* the retrieved salt, and compare it to the stored hashed password.

   # Example Python using bcrypt
   stored_salt = # Retrieve from database
   hashed_entered_password = bcrypt.hashpw(entered_password.encode('utf-8'), stored_salt)
   if hashed_entered_password == stored_hashed_password:
     # Authentication successful!
   

2. Data Encryption

Encrypt sensitive data before storing it in your database.

1. Choose an Encryption Algorithm: AES (Advanced Encryption Standard) is a widely used and secure symmetric encryption algorithm. Use a library that handles the details correctly.
2. Generate Encryption Keys: You’ll need an encryption key to encrypt and decrypt data. Important: Do *not* store this key in your code or database directly! See section 3 for key management.
3. Encryption Process: Before storing the data, encrypt it using AES with the encryption key.

   # Example Python using cryptography library
   from cryptography.fernet import Fernet
   key = # Retrieve from secure storage (see Section 3)
   f = Fernet(key)
   token = f.encrypt(data.encode('utf-8'))
   

4. Decryption Process: After successful login, retrieve the encrypted data and decrypt it using AES with the same encryption key.

   # Example Python using cryptography library
   from cryptography.fernet import Fernet
   key = # Retrieve from secure storage (see Section 3)
   f = Fernet(key)
   decrypted_data = f.decrypt(token).decode('utf-8')
   

3. Key Management

This is the most critical part! Poor key management defeats all other security measures.

1. Never Hardcode Keys: Storing keys directly in your code or database is a major security risk.
2. Key Storage Options:
   • Hardware Security Module (HSM): The most secure option, but also the most expensive.
   • Key Management Service (KMS): Cloud providers offer KMS services (e.g., AWS KMS, Google Cloud KMS). These provide a secure way to store and manage keys.
   • Encrypted Configuration File: A less secure option, but better than hardcoding. Encrypt the configuration file containing the key with a separate master key that is carefully protected.
3. Key Rotation: Regularly change your encryption keys to limit the impact of a potential compromise.

4. Putting it Together

The typical flow looks like this:

1. User attempts login.
2. System retrieves user’s salt from database.
3. System hashes entered password with retrieved salt.
4. System compares hashed password to stored hash.
5. If authentication succeeds:
   • System retrieves encryption key from secure storage (KMS, HSM etc.).
   • System retrieves encrypted data from database.
   • System decrypts data using retrieved key.
   • Data is now available to the user.

5. Important Considerations

• HTTPS: Always use HTTPS to encrypt communication between the client and server.
• Input Validation: Validate all user input to prevent injection attacks.
• Regular Security Audits: Have your system regularly audited by security professionals.
• Cyber security best practices: Stay up-to-date with current cyber security threats and vulnerabilities.