presalting

Presalting is a technique used in the field of cryptography to enhance the security of password storage. The process involves adding a unique, random value, known as a salt, to each password before hashing. This salt is typically concatenated with the password and then hashed together. The resulting hash, along with the salt, is stored in a database. When a user attempts to log in, the system retrieves the salt associated with the stored hash, concatenates it with the entered password, hashes the result, and compares it to the stored hash.

The primary purpose of presalting is to protect against precomputed attacks, such as rainbow table attacks. Rainbow tables are precomputed tables of hashes for common passwords, which can be used to quickly reverse-engineer hashed passwords. By adding a unique salt to each password, the resulting hash is unique, making it much more difficult for an attacker to use a rainbow table to find the original password.

Presalting also helps to mitigate the risk of password reuse. If a user reuses the same password across multiple services, an attacker who compromises one service may be able to use the same password to access other services. By using a unique salt for each password, even if an attacker obtains the hashed passwords from multiple services, they would still need to compute the hash for each password individually, making it much more difficult to crack them.

In summary, presalting is a crucial technique in password security that enhances the protection of stored passwords by making them unique and resistant to precomputed attacks. It is a standard practice in modern cryptographic systems to ensure the security of user credentials.