What is Bcrypt Hash?
Bcrypt (Blowfish Crypt) is a password-hashing function designed to securely store passwords by converting them into irreversible hashes. It was specifically created to address vulnerabilities in older password hashing algorithms like MD5 and SHA1, which were fast and unsuitable for securely storing passwords due to their susceptibility to brute-force attacks.
The primary goal of using bcrypt is to make it computationally expensive and time-consuming for attackers to crack the password hashes even if they get access to the hash values. This is achieved through the following features:
1. Key Stretching: Bcrypt uses a configurable number of iterations to hash the password. The more iterations, the slower the hashing process becomes, making it more difficult for attackers to try a large number of passwords in a short amount of time.
2. Salting: Bcrypt automatically generates a random salt for each password before hashing it. A salt is a random value that is concatenated with the password before hashing, ensuring that even if two users have the same password, their hashed values will be different. This prevents attackers from using precomputed tables (rainbow tables) to reverse the hashes.
3. Adaptive Work Factor: Bcrypt has a built-in feature that allows it to automatically adjust the work factor (number of iterations) over time. This means that as computing power increases, the work factor can be increased to maintain the desired level of security.
The resulting bcrypt hash is a fixed-length string that includes the salt, the cost factor, and the actual password hash. An example of a bcrypt hash might look like this:
In PHP, you can use the `password_hash` function to generate bcrypt hashes, and `password_verify` to verify a password against a stored hash. It's important to use bcrypt or other strong password-hashing algorithms to enhance the security of user passwords and protect against various password-related attacks.