How to implement secure storage of password hashes in a server-side database?

For secure storage of user credentials, developers must never store passwords in plain text. Instead, cryptographic hashing is used utilizing specialized slow algorithms such as Argon2, bcrypt, or PBKDF2. These functions transform the entered string into a unique fixed-length character sequence that cannot be reversed to obtain the original password.

The main vulnerability of standard hash functions lies in their high processing speed, which allows attackers to brute-force millions of combinations per second using GPUs. Modern algorithms intentionally slow down the hash computation process and require large amounts of RAM. This makes brute-force attacks and the use of rainbow tables economically unviable for cybercriminals even in the event of a leak of the entire database.

A key element of protection is adding a salt to each password before hashing. Salt is a random string of characters unique to each individual user. Even if two people use the same simple password, their resulting hashes in the database will be completely different due to the uniqueness of the salt. The salt is stored in plain text next to the hash, since its task is to prevent the use of pre-prepared guessing tables.

The process of checking a password entered at login looks as follows. The system takes the specific user's salt from the database, combines it with the entered password, and passes it through the same hashing function. If the resulting result completely matches the value saved in the database, authorization is considered successful. Otherwise, access is blocked without indicating whether the login or password was incorrect.

Over time, computing power grows, so hashing parameters must be periodically updated. When a user successfully authorizes in the system, the server can check the relevance of the current algorithm settings and, if necessary, automatically rehash the password with higher resource requirements. Such an approach guarantees the continuous adaptation of the security system to new technological threats.