Password Hashing
Password hashing is a fundamental security technique used to protect user passwords stored in databases or any data storage systems. This method transforms a password into another string of characters using a mathematical algorithm, making it difficult for attackers to retrieve the original password even if they gain access to the stored data.
History
The concept of password hashing has evolved significantly since its inception:
- Early Days: In the early days of computing, passwords were often stored in plaintext or with very basic forms of encryption. The Unix operating system in the 1970s introduced the concept of hashing passwords using the
crypt function, which used DES (Data Encryption Standard) for hashing.
- Development of MD5 and SHA: In the late 1980s and 1990s, cryptographic hash functions like MD5 and SHA-1 were developed, initially used for data integrity but soon adapted for password hashing due to their one-way nature.
- Modern Hashing Algorithms: As computational power increased, vulnerabilities in these algorithms were discovered, leading to the development of more robust hashing algorithms like bcrypt, scrypt, and Argon2. Argon2 was the winner of the Password Hashing Competition (PHC) in 2015, designed to be resistant to GPU-based attacks and to provide a configurable level of computational overhead.
Context and Importance
Password hashing is critical for several reasons:
- Security: It ensures that even if a database is compromised, the passwords themselves remain secure because the hash cannot be reversed to reveal the original password.
- Salting: To counter dictionary attacks and rainbow table attacks, salts are used. A salt is a random string that is combined with the password before hashing. This makes precomputed tables ineffective and ensures that identical passwords have different hashes.
- Password Cracking Resistance: Modern algorithms like bcrypt incorporate work factors or cost parameters that allow for the hashing process to be slowed down, making brute-force attacks more time-consuming and computationally expensive.
Key Algorithms
Here are some of the prominent algorithms used in password hashing:
- bcrypt: Designed by Niels Provos and David Mazières in 1999, bcrypt incorporates an adaptive cost factor to slow down the hashing process, making it resistant to brute-force attackssource.
- scrypt: Developed by Colin Percival in 2009, it is designed to use more memory than bcrypt, making it more resistant to hardware-based attackssource.
- Argon2: The winner of the PHC in 2015, Argon2 has variants (Argon2d, Argon2i, and Argon2id) tailored for different security contexts, providing resistance against both side-channel attacks and time-memory trade-off attackssource.
Best Practices
- Always use a unique salt for each password.
- Choose modern hashing algorithms with configurable cost factors.
- Implement a pepper, a secret key stored outside the database, to add an extra layer of security.
- Regularly update the work factor of your hashing function to keep pace with hardware advancements.