Password-Based Key Derivation

Password-Based Key Derivation

Password-Based Key Derivation (PBKDF) is a cryptographic technique used to derive cryptographic keys from passwords or passphrases. PBKDF algorithms apply a one-way function, along with additional parameters such as salt and iteration count, to transform a password into a cryptographic key suitable for encryption, authentication, or other cryptographic operations. PBKDF techniques are commonly used to enhance the security of password storage, key derivation, and cryptographic key management systems.

Purpose

The purpose of Password-Based Key Derivation is to:

• Enhance Password Security: Derive cryptographic keys from passwords to improve their security and resilience against brute-force attacks, dictionary attacks, or password guessing attacks.
• Protect Sensitive Information: Use derived keys to encrypt sensitive data, authenticate users, or secure communication channels, ensuring the confidentiality, integrity, and authenticity of information.
• Support Key Management: Generate cryptographic keys for various cryptographic operations, such as encryption, decryption, digital signing, or key exchange, based on user passwords or passphrases.
• Enable Password-Based Authentication: Derive authentication tokens or session keys from passwords to authenticate users and establish secure communication channels in password-based authentication protocols, such as SRP (Secure Remote Password) or PAKE (Password Authenticated Key Exchange).

PBKDF Algorithms

Several PBKDF algorithms are commonly used in practice, including:

• PBKDF2 (Password-Based Key Derivation Function 2): A widely adopted PBKDF algorithm standardized in RFC 2898 that applies a pseudorandom function, such as HMAC (Hash-based Message Authentication Code), iteratively to derive cryptographic keys from passwords, using a salt value and an iteration count to enhance security.
• bcrypt: A key derivation algorithm based on the Blowfish cipher designed for password hashing, which applies the Eksblowfish algorithm iteratively using a cost parameter to adjust the computational effort required for key derivation.
• scrypt: A memory-hard key derivation function designed to resist brute-force and dictionary attacks by requiring a significant amount of memory and computational resources, making it suitable for password-based key derivation in resource-constrained environments.

Parameters

PBKDF algorithms typically use the following parameters:

• Password: The user-provided password or passphrase used as input to the key derivation function.
• Salt: A random or pseudorandom value used to add variability to the derived keys, preventing precomputation attacks and rainbow table attacks.
• Iteration Count: The number of iterations or rounds of the key derivation function applied to the password and salt to increase the computational cost of key derivation and enhance security.
• Key Length: The length of the derived cryptographic key, which determines the cryptographic strength and entropy of the resulting keys.

Best Practices

To ensure the security and effectiveness of Password-Based Key Derivation, organizations can follow these best practices:

• Use Established Algorithms: Use well-established and standardized PBKDF algorithms, such as PBKDF2, bcrypt, or scrypt, that have undergone rigorous cryptographic analysis and testing.
• Configure Parameters Appropriately: Configure PBKDF parameters, such as salt length, iteration count, and key length, based on security requirements, performance considerations, and cryptographic strength requirements.
• Salt Generation: Use a cryptographically secure random number generator (CSPRNG) to generate unique salt values for each password to prevent rainbow table attacks and enhance the randomness of derived keys.
• Iterative Key Derivation: Use a sufficient number of iterations in the key derivation process to increase the computational cost of key derivation and slow down brute-force or dictionary attacks.
• Regular Updates: Regularly update password-based key derivation mechanisms, algorithms, and parameters to adapt to evolving security threats, cryptographic attacks, and best practices.

Conclusion

Password-Based Key Derivation is a fundamental cryptographic technique used to derive cryptographic keys from passwords or passphrases for various security and authentication purposes. By employing secure PBKDF algorithms, configuring parameters appropriately, and following best practices, organizations can enhance the security of password-based authentication, key management, and cryptographic operations.