How can you choose a secure hash function for password storage?

1 What is a hash function?

Hash functions are mathematical functions that take any input and produce a fixed-length output, known as a hash or a digest. The output should depend solely on the input, and not on any other factors. For a hash function to be effective, it must possess one-wayness or preimage resistance, which means it should be easy to compute the hash from the input, but hard to find the input from the hash. It should also be difficult to find two different inputs that produce the same hash (collision resistance), and hard to predict how the hash will change when the input changes slightly (avalanche effect). These functions are used in cryptography, data integrity, digital signatures, and other applications; for password storage they help prevent attackers from reading or guessing passwords even if they have access to the database where the hashes are stored.

3 What are the risks of using a hash function for password storage?

Using a hash function for password storage is not foolproof, and there are still some risks to be aware of and mitigate. For example, brute force attacks involve an attacker hashing every possible password until they find a match. This can be done faster if the attacker has access to powerful computing or a rainbow table. Additionally, dictionary attacks involve an attacker using a list of common passwords and hashing them until they find a match. This can be done faster if the attacker knows something about the user, such as their name or birthday. Lastly, hash function weaknesses can be exploited by an attacker to find collisions or preimages faster than expected, compromising the security and integrity of the hashes and passwords.

4 How to choose a secure hash function for password storage?

When choosing a secure hash function for password storage, you need to take into account several factors, such as the security level, performance, and standardization. The hash function should be resistant to brute force, dictionary, and hash function attacks, with a high level of one-wayness, collision resistance, and avalanche effect. It should also be updated and maintained regularly to fix any bugs or weaknesses. Additionally, the hash function should be fast enough to compute the hashes without causing delays or errors in the user experience, as well as scalable and compatible with your system and database. Moreover, it should be based on a widely accepted and tested standard, such as SHA-2 or SHA-3, supported by reputable and trustworthy sources like NIST or IETF.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?