Password hashing is a fundamental aspect of securing passwords, transforming the password storage landscape from plain text to encrypted hashes. This article explores the evolution of password hashing, from early algorithms like MD5 and SHA-1 to the more secure methods recommended today, concluding with the importance of using random passwords for each website.
Understanding Hashing
Before diving deeper into the history and evolution of password hashing, it's important to understand what hashing is. Hash functions, the methods that do the hashing, are designed to take any string of data, or "input," and produce a fixed-size string of bytes, typically known as a "hash." This process has several key characteristics that make it particularly useful for security purposes.
One crucial feature of hash functions is their sensitivity to input changes. This is known as the avalanche effect. Even a minor alteration in the input—such as changing a single character in a password—will produce a completely different hash. For example, the hashes for the strings "password1" and "password2" will look entirely dissimilar, even though the only difference between the two inputs is the last character. This characteristic is vital for maintaining data integrity, as it makes it nearly impossible to infer the original input from the hash alone.
Furthermore, hash functions are one-way functions. This means that they are designed to be computationally infeasible to reverse. The output (the hash) does not retain specific details about the input that would allow someone to reconstruct the original data without extraordinary computational effort. The only feasible way to "reverse" a hash is through a method called brute-forcing, where every possible combination of the original data is hashed again until a matching hash is found.
Early Days: MD5 and SHA-1
In the early days of digital security, MD5 (Message-Digest Algorithm 5) and SHA-1 (Secure Hash Algorithm 1) were widely used for password hashing. Developed during the early '90s, these algorithms converted plain text passwords into fixed-size hash values. Despite their initial security, vulnerabilities such as susceptibility to collision attacks soon rendered them obsolete for secure applications.
Password-Based Key Derivation Functions (PBKDFs)
While hash functions are designed to be fast and efficient, this feature can be detrimental when it comes to password security because it makes brute-force attacks easier. Password-Based Key Derivation Functions (PBKDFs), such as PBKDF2, bcrypt, and scrypt, are designed to counteract these attacks by incorporating a salt (to defend against rainbow table attacks) and employing a technique known as key stretching. Key stretching intentionally slows down the hashing process, which can significantly deter attempts at unauthorized access.
The Evolution to More Secure Hashing
As cybersecurity advanced, the inadequacies of early hashing algorithms like MD5 and SHA-1 became apparent, prompting the development of algorithms specifically designed for password security, such as bcrypt, scrypt, and Argon2 or so called Password-Based Key Derivation Functions (PBKDFs).
OWASP Recommendations
According to OWASP, the recommended algorithms for password hashing are bcrypt, scrypt, and Argon2. These are preferred for their robust defense against brute-force attacks and their built-in mechanisms for salt and key stretching.
bcrypt
bcrypt is a password hashing function derived from the Blowfish cipher. It incorporates a salt to protect against rainbow table attacks and uses a cost parameter to increase the computation time (and thus the difficulty) of generating the hash. This cost factor is adjustable, allowing the algorithm to be scaled with hardware improvements.
Key Parameters:
- Cost factor: Controls the amount of key expansion rounds; higher values increase security but also make the hashing process slower.
OWASP recommends to use a work factor of 10 or more with a password limit of 72 bytes.
scrypt
scrypt is designed to be both memory and time-intensive to resist large-scale custom hardware attacks. It can be configured to require a specific amount of memory, and it also includes a salt and an iteration count, similar to PBKDF2.
Key Parameters:
- N (CPU/memory cost): Determines the number of iterations, which directly affects memory and CPU usage.
- r (block size): Adjusts the block size, influencing memory usage and mixing time.
- p (parallelization parameter): Specifies the number of parallel threads that can be run; used to tune the algorithm to the number of cores.
OWASP recommends to use a minimum CPU/memory cost parameter of (2^17), a minimum block size of 8 (1024 bytes), and a parallelization parameter of 1.
Argon2
Argon2, the winner of the Password Hashing Competition in 2015, comes in two variants: Argon2d and Argon2i. Argon2d is optimized for environments where the threat from side-channel attacks is low, while Argon2i is optimized to resist side-channel attacks. It also incorporates key features from both bcrypt and scrypt.
Key Parameters:
- Memory cost: Specifies the amount of memory used during the hashing process.
- Time cost: Determines the amount of computation realized and influences the hashing time.
- Parallelism: Defines the number of threads to be used during the hashing process.
OWASP recommends to use Argon2id with a minimum configuration of 19 MiB of memory, an iteration count of 2, and 1 degree of parallelism.
Given the evolving nature of security threats and countermeasures, it's crucial to stay updated with the latest practices in password security. For the most current and comprehensive recommendations, please refer to the OWASP Password Storage Cheat Sheet at OWASP's official site. Ensure to review these guidelines regularly to align with the best practices in cybersecurity.
The Importance of Random Passwords
While employing modern hashing algorithms is crucial, the manner in which passwords are created and managed also play a critical role in maintaining security. Random passwords for each website are essential due to several factors:
- Legacy Systems: Many websites still use outdated hashing algorithms or, worse, store passwords in cleartext. These practices leave user data extremely vulnerable to theft and misuse.
- Cross-Site Security: If one site with weak security is compromised, unique passwords ensure that other accounts remain secure.
- Automated Attacks: Using complex, unique passwords reduces the risk of falling victim to automated attacks that exploit common passwords and known hashing weaknesses.
Conclusion
From MD5 and SHA-1 to modern algorithms like bcrypt and Argon2, password hashing has undergone significant transformations. As cyber threats continue to evolve, adopting modern hashing algorithms and ensuring the use of random, unique passwords for each website are essential practices for safeguarding online security. These strategies not only prevent the compromise of individual accounts but also strengthen the overall security posture against increasingly sophisticated attacks.
