Hash library in PHP8.0: Bcrypt

In PHP8.0, the hash function library introduces a new hash algorithm: Bcrypt. Bcrypt is a password hash function that limits the maximum length of the input password and greatly increases the security of password cracking by increasing the complexity of the algorithm.

Before PHP8.0, password hash functions mainly used algorithms such as MD5 or SHA-1. The weakness of these algorithms is that the hash values they produce are very short, only 32 or 40 bytes. In this case, the attacker can crack the password through brute force method. In contrast, Bcrypt is a more secure hashing algorithm due to its longer hash value length and difficulty in reversing.

The characteristic of the Bcrypt algorithm is that it limits the length of the input password to 72 characters. This restriction is purposeful to prevent some malicious users from exploiting vulnerabilities in the hash algorithm to carry out attacks. On the other hand, Bcrypt can also use multiple rounds of iterative calculations of hash values to increase the complexity and time-consuming of cracking passwords.

In addition to password length restrictions and multiple rounds of iterative calculations, the Bcrypt algorithm also introduces the concept of "salt". The salt is a random string of characters that is added to the original password to generate the final hash value. This approach can prevent attackers from using tools such as rainbow tables to reversely crack the hash results. At the same time, salt can also make the hash result different every time, which increases the difficulty for attackers to use more complex methods to crack the password.

The PHP8.0 related functions that use the Bcrypt algorithm for password hashing mainly include the following:

1. password_hash
   This function is used to generate a hash value of a password. The function signature is:

string password_hash(string $password, int $algo, array $options = array())

Among them, $password is to be The hashed original password, $algo is the hashing algorithm type, and $options are the configuration parameters. When using Bcrypt for password hashing, the value of $algo should be PASSWORD_BCRYPT.

2. password_verify
   This function is used to verify whether a password is consistent with its hash value. The function signature is:

bool password_verify(string $password, string $hash)

Among them, $password is the password to be verified, $hash is the password that has been verified Generated password hash. Returns true if the password and hash match, false otherwise.

3. password_needs_rehash
   This function is used to verify whether a hash value needs to be recalculated. The function signature is:

bool password_needs_rehash(string $hash, int $algo, array $options = array())

where $hash is to be Verified hash value, $algo is the hash algorithm type, $options are configuration parameters. This function can recalculate a hash value into a new hash value to adapt to higher security requirements.

In short, the Bcrypt hashing algorithm introduced in PHP8.0 provides applications with stronger password security. In practical applications, using the Bcrypt algorithm for password hashing is a very good choice.

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