What are the best methods to hash a password securely?

Hashing is a one-way function, meaning once data is transformed into a hash, it cannot be easily reversed to obtain the original input.

This is critical for password security as it hides the actual password from anyone who accesses the database.

Salting is the practice of adding a unique, random piece of data to each password before hashing.

This ensures that even if two users have the same password, they will have different hashes stored in the database.

Common hashing algorithms like SHA-256 are not specifically designed for password hashing.

They are optimized for speed and can be vulnerable to brute-force attacks when used for password storage.

Slow hashing functions, such as bcrypt, Argon2, and PBKDF2, are preferred for password hashing because they require more computational resources, making brute-force attacks significantly more time-consuming.

Memory-hard hashing algorithms, like Argon2, have been specifically engineered to make it difficult for attackers to leverage hardware acceleration in cracking hashed passwords, providing an additional security layer.

A "pepper" is an additional secret value added to the hash but not stored with the hash.

It must be hardcoded in the application and complicates unauthorized access to the password hashes, even if an attacker acquires the database.

Hash length matters: Longer hashes generally provide better security.

For instance, SHA-256 generates a 256-bit hash, while bcrypt typically produces a 60-character string, which is considerably longer and more complex.

Hashes must be stored securely; using a secure connection (like HTTPS) when transmitting and only accessing hashes in memory, not writing them to logs, prevents exposing them to attackers.

An essential aspect of password hashing is to ensure that the hash function is resistant not only to collisions (producing the same hash for different inputs) but also to preimage attacks (finding the original input from a hash).

Passwords should not be hashed alone; they need to be concatenated with a salt before hashing.

This is crucial for preventing precomputation attacks where attackers generate hashes for common password choices beforehand.

Historical context shows that older hashing algorithms like MD5 and SHA-1 have been rendered insecure due to advancements in cracking technologies, making them unsuitable for modern password security needs.

Password hashing should consider human factors, and organizations can help users choose stronger passwords by enforcing complexity requirements and educating them on the importance of unique passwords.

Rate limiting on login attempts is critical, as it helps to slow down automated attacks that guess passwords.

This approach makes it harder for attackers to execute rapid brute-force attempts.

A password manager can generate and store complex passwords, relieving users of the burden of remembering complex strings while ensuring that each service is accessed with a unique password.

Researchers have shown that the "rainbow table," a precomputed table for reversing cryptographic hash functions, is mitigated by effectively using a unique salt for every password stored.

The NIST (National Institute of Standards and Technology) has updated its recommendations for password storage, pushing for the abandonment of outdated algorithms and promoting the use of slow hashing methods.

Vestigial design flaws, like storing passwords with the same salt, can lead to vulnerabilities in large databases.

Each user must have a unique salt and appropriate hashing strategy to prevent bulk cracking.

The concept of "key stretching" involves repeatedly hashing a password to increase the time needed to carry out an attack, making algorithms like PBKDF2 particularly effective for increasing security.

Security breaches underscore the necessity of auditing authentication systems.

Regularly checking for security vulnerabilities and updating hashing algorithms in line with emerging best practices can deter attacks.

Understanding the differentiation between authentication and authorization is essential; hashing is primarily a mechanism for securing authentication data, ensuring that unauthorized parties cannot easily access user credentials.