Explain secure password hashing in PHP (e.g., password_hash, password_verify). Why not use MD5 or SHA1?

In PHP, password_hash and password_verify functions should be used to implement secure password hashing, and MD5 or SHA1 should not be used. 1) password_hash generates a hash containing salt values ​​to enhance security. 2) password_verify to verify the password and ensure security by comparing the hash value. 3) MD5 and SHA1 are vulnerable and lack salt values, and are not suitable for modern password security.

introduction

In the age of network security, password security is crucial. Today we are going to explore how to implement secure password hashing in PHP and why old methods like MD5 or SHA1 should not be used. Through this article, you will learn not only how to use password_hash and password_verify functions, but also understand the principles and best practices behind it. Let’s unveil the mystery of security password hashing!

Review of basic knowledge

Before we start to dive into it, let's first review what a hash function is. The hash function can convert inputs of any length into outputs of fixed lengths, which is widely used in cryptography. Traditional hash functions such as MD5 and SHA1 are fast, but they have proven to be insecure enough in modern password security.

In PHP, password_hash and password_verify are functions designed specifically for password security. They use more modern and secure hashing algorithms such as bcrypt.

Core concept or function analysis

Definition and function of secure password hash

Secure password hashing refers to the use of a strong hashing algorithm to process the user's password, making it difficult for an attacker to invert the original password through the hash value even if the database is compromised. The password_hash function is such a tool that can generate a hash value containing salt values, greatly increasing the difficulty of cracking.

Let's look at a simple example:

 $password = 'mySecurePassword';
$hash = password_hash($password, PASSWORD_BCRYPT);
echo $hash;

This code snippet uses the PASSWORD_BCRYPT algorithm, which is an option of password_hash function, ensuring the secure hash of the password.

How it works

The working principle of password_hash is like this: it first generates a random salt value, and then hash the salt value and the original password together with the bcrypt algorithm. The generated hash contains both the salt value and hash result, which makes each user's password hash unique, even if they use the same password.

The password_verify function is used to verify the password. It extracts the salt value in the hash value, and then hash the input password using the same bcrypt algorithm and compares it with the stored hash value. If it matches, the verification passes.

The advantage of this approach is that it not only increases the cracking difficulty, but also resists rainbow table attacks, as each password has a unique salt value.

Example of usage

Basic usage

Let's see how to use password_hash and password_verify in real applications:

 // hash password $userPassword = 'user123';
$hashedPassword = password_hash($userPassword, PASSWORD_BCRYPT);

// Verify password $inputPassword = 'user123';
if (password_verify($inputPassword, $hashedPassword)) {
    echo 'Password is valid!';
} else {
    echo 'Invalid password.';
}

This code shows how to create a hash password and how to verify it. Note that password_hash generates a different hash value each time it runs, because it uses random salt values.

Advanced Usage

In some cases, you may want to use more advanced options to enhance password security. For example, you can specify the hash cost to increase the calculation time and thus increase the cracking difficulty:

 $options = [
    'cost' => 12,
];
$hashedPassword = password_hash($userPassword, PASSWORD_BCRYPT, $options);

In this example, we set cost to 12, which increases the hash calculation time, thereby further improving security. However, it should be noted that too high costs may affect performance.

Common Errors and Debugging Tips

A common mistake is to try to compare hash values ​​directly, which is incorrect because the hash values ​​generated are different each time. Another common problem is using old hashing algorithms like MD5 or SHA1, which can cause security issues.

One of the debugging tips is to use the password_needs_rehash function to check if the password needs to be rehashed, especially after you upgrade the hashing algorithm or options:

 if (password_needs_rehash($hashedPassword, PASSWORD_BCRYPT, $options)) {
    $newHash = password_hash($userPassword, PASSWORD_BCRYPT, $options);
    // Update the hash value in the database}

Performance optimization and best practices

In practical applications, optimizing the performance of password hashing is an important topic. The password_hash function is already quite efficient, but you can find a balance between security and performance by tuning the cost parameters.

A best practice is not to regenerate the hash every time the user logs in, but to rehash when the user changes his password or system upgrades. This reduces unnecessary computational overhead.

Another best practice is to make sure your database is secure enough, because even with password_hash , attackers can still try brute force if the database is compromised.

Why not use MD5 or SHA1?

MD5 and SHA1 were early hashing algorithms that have proven to be insecure enough in modern cryptographic security. Here are a few reasons:

• Collision Attack : MD5 and SHA1 are vulnerable to collision attacks, that is, finding two different inputs to produce the same output. This is fatal to password hashing, as attackers can exploit this to crack passwords.

• Too fast : MD5 and SHA1 are very fast computing, which makes them easier to be brute-forced. Modern password hashing algorithms such as bcrypt are deliberately designed to have slower calculations to increase the difficulty of cracking.

• Lack of salt values : Traditional MD5 and SHA1 hashes usually do not contain salt values, which makes them vulnerable to rainbow table attacks. password_hash contains salt values ​​by default, greatly increasing the difficulty of cracking.

• Unable to upgrade : MD5 and SHA1 do not have built-in mechanisms to upgrade the hash algorithm, while password_hash and password_verify can easily upgrade the hash algorithm through password_needs_rehash function.

In general, using password_hash and password_verify is the best practice in PHP for implementing secure password hashing. They not only provide higher security, but also provide convenient upgrades and verification mechanisms to ensure that your user passwords remain secure in future cybersecurity challenges.

Hopefully, through this article, you not only have a grasp on how to use password_hash and password_verify in PHP, but also understand why these methods are safer than MD5 or SHA1. Remember that password security is an ongoing process, and keeping learning and updating is the best protection.

The above is the detailed content of Explain secure password hashing in PHP (e.g., password_hash, password_verify). Why not use MD5 or SHA1?. For more information, please follow other related articles on the PHP Chinese website!