Argon2 Password Hash Generator

What is Argon2?

Argon2 is a key derivation function designed specifically for password hashing and credentials protection. As the winner of the 2015 Password Hashing Competition (PHC), it represents the current state-of-the-art in password security, offering strong protection against various attack vectors including brute force, side-channel, and time-memory trade-off attacks.

Understanding Argon2 Variants

Argon2 comes in three variants, each optimized for different security priorities:

Argon2id is generally recommended for most applications as it provides a good balance between resistance to side-channel attacks and GPU-based cracking attempts.

Key Parameters of Argon2

Argon2's security and performance are controlled by these key parameters:

1. Memory Cost (m)

The amount of memory required by the algorithm, measured in kilobytes. Higher values require more memory, making hardware-based attacks more expensive.

2. Time Cost (t)

The number of iterations, controlling how computationally intensive the hashing will be. Higher values increase security but also increase processing time.

3. Parallelism (p)

The number of parallel threads used during the hash computation. This should typically be set to the number of available CPU cores to maximize efficiency.

Higher parallelism can improve performance on multi-core systems but doesn't necessarily increase security proportionally. Setting it beyond your available CPU cores typically doesn't improve performance.

Understanding Argon2 Hash Format

An encoded Argon2 hash string follows this format:

$argon2id$v=19$m=65536,t=3,p=4$c2FsdHNhbHRzYWx0c2FsdA$RVZ7MR2V3LAZXCCWxs4sBuMYh8iARZP3HOYnQS2fPJg

Breaking down the components:

Recommended Parameters for Different Scenarios

The goal is to choose parameters that make the hash function take about 500ms on your server. This is slow enough to deter attackers but fast enough not to impact user experience significantly.

Argon2 vs. Other Password Hashing Algorithms

Implementing Argon2 in Different Languages

PHP (7.2+)

// Generate a password hash
$hash = password_hash('user_password', PASSWORD_ARGON2ID, [
    'memory_cost' => 65536, // 64 MB
    'time_cost'   => 4,     // 4 iterations
    'threads'     => 2      // 2 threads
]);

// Verify a password
if (password_verify('user_password', $hash)) {
    echo "Password is valid!";
} else {
    echo "Password is invalid!";
}

Python

from argon2 import PasswordHasher

# Create a password hasher
ph = PasswordHasher(
    time_cost=4,        # Iterations
    memory_cost=65536,  # 64 MB
    parallelism=2,      # 2 threads
    hash_len=32,        # 32 bytes output
    type=2              # Argon2id (0=Argon2d, 1=Argon2i, 2=Argon2id)
)

# Hash a password
hash = ph.hash("user_password")

# Verify a password
try:
    ph.verify(hash, "user_password")
    print("Password is valid!")
except:
    print("Password is invalid!")

Node.js

const argon2 = require('argon2');

async function hashPassword() {
    try {
        // Generate a hash
        const hash = await argon2.hash("user_password", {
            type: argon2.argon2id,
            memoryCost: 65536,  // 64 MB
            timeCost: 4,        // 4 iterations
            parallelism: 2      // 2 threads
        });
        console.log("Hash:", hash);
        
        // Verify a hash
        const isValid = await argon2.verify(hash, "user_password");
        if (isValid) {
            console.log("Password is valid!");
        } else {
            console.log("Password is invalid!");
        }
    } catch (err) {
        console.error("Error:", err);
    }
}

Java

import com.kosprov.jargon2.api.Jargon2;

// Create a password hasher
Jargon2.Hasher hasher = Jargon2.jargon2Hasher()
    .type(Jargon2.Type.ARGON2id)
    .memoryCost(65536)    // 64 MB
    .timeCost(4)          // 4 iterations
    .parallelism(2)       // 2 threads
    .encodedHash();

// Generate a hash
String hash = hasher.password("user_password".getBytes()).hash();

// Verify a hash
boolean isValid = Jargon2.jargon2Verifier()
    .hash(hash)
    .password("user_password".getBytes())
    .verifyEncoded();

Security Best Practices with Argon2

Parameter Selection Strategy

When selecting parameters for Argon2:

1. Start with the recommended defaults for your use case
2. Benchmark on your target hardware to find values that take ~500ms
3. Maximize memory cost within your constraints
4. Adjust time cost to achieve your target hash time
5. Set parallelism to match available CPU cores

Migrating to Argon2 from Other Algorithms

If you're currently using an older hashing algorithm, here's a gradual migration approach:

1. Update new passwords immediately

// Store new passwords with Argon2
$hash = password_hash($password, PASSWORD_ARGON2ID, [
    'memory_cost' => 65536,
    'time_cost' => 4,
    'threads' => 2
]);

2. Migrate existing passwords on successful login

// Check password against existing hash (e.g., bcrypt)
if (password_verify($password, $old_hash)) {
    // Login successful - rehash with Argon2
    if (password_needs_rehash($old_hash, PASSWORD_ARGON2ID, [
        'memory_cost' => 65536,
        'time_cost' => 4,
        'threads' => 2
    ])) {
        // Update stored hash to new Argon2 hash
        $new_hash = password_hash($password, PASSWORD_ARGON2ID, [
            'memory_cost' => 65536,
            'time_cost' => 4,
            'threads' => 2
        ]);
        // Save $new_hash to database
    }
    // Continue with successful login
}

Conclusion

Argon2 represents the current state-of-the-art in password hashing technology. Its memory-hard design and configurable parameters make it extremely resistant to hardware-based attacks while allowing developers to balance security and performance based on their specific requirements.

By following the guidelines presented here and selecting appropriate parameters for your application, you can significantly enhance the security of your users' credentials and protect against both current and future password cracking attempts.

Remember that password hashing is just one component of a comprehensive security strategy. Even the strongest hashing algorithm should be complemented with other security measures like rate limiting, multi-factor authentication, and proper security monitoring.