How to Use Argon2 for Password Hashing in Go

Password hashing is a critical component of securing user data in web applications. The Go programming language offers strong cryptographic capabilities, and among them, Argon2 is a recommended choice for password hashing. In this article, we'll explore how to implement Argon2 for password hashing in a Go application.

What is Argon2?

Argon2 is a secure cryptographic hashing algorithm designed for password hashing. It is the winner of the 2015 Password Hashing Competition and was praised for its strong resistance against both GPU and side-channel attacks. Argon2 has three variants: Argon2d (data-dependant), Argon2i (data-independent) and Argon2id, a hybrid of the two. Argon2id is recommended for password hashing.

Setting Up Argon2 in Go

To use Argon2 in Go, we'll be using the golang.org/x/crypto package, which includes an implementation of Argon2. First, ensure that you have Go installed and your workspace is configured.

go get golang.org/x/crypto

Hashing Passwords with Argon2

Let's dive into the code for hashing passwords. Below is a step-by-step example of how to hash and verify passwords using Argon2 in Go.

Hashing a Password

package main

import (
	"fmt"
	"log"
	"golang.org/x/crypto/argon2"
)

func hashPassword(password string, salt []byte) []byte {
	return argon2.IDKey([]byte(password), salt, 1, 64*1024, 4, 32)
}

func main() {
	password := "mySuperSecretPassword"
	salt := []byte("somesalt123") // In a real application, use a securely generated random salt
	hashedPassword := hashPassword(password, salt)
	fmt.Printf("Hashed password: %x\n", hashedPassword)
}

In the above code, argon2.IDKey() is used to hash the password using the Argon2id variant. It takes the following arguments:

• password: The password to hash as a byte slice.
• salt: A unique salt for each password, ideally randomly generated.
• time: The amount of computational effort required (here, set to 1).
• memory: Amount of memory usage as in-kilobyte (here, 64*1024 KB or 64 MB)
• threads: Degree of parallelism (here, set to 4).
• keyLength: The desired length of the key (here set to 32 bytes).

Verifying a Password

To verify a password, simply hash it again with the same parameters and compare it to the stored hash.

func verifyPassword(password string, salt, hash []byte) bool {
	newHash := hashPassword(password, salt)
	return string(newHash) == string(hash)
}

func main() {
	password := "mySuperSecretPassword"
	salt := []byte("somesalt123")
	hashedPassword := hashPassword(password, salt)
	
	if verifyPassword(password, salt, hashedPassword) {
		fmt.Println("Password is correct!")
	} else {
		fmt.Println("Password is incorrect!")
	}
}

The verifyPassword function compares the hashed version of the password input with the original hash to determine if they match.

Best Practices

• Use a different salt for each password. Salts mitigate the impact of rainbow table attacks and should ideally be generated using a secure random generator.
• Configuration matters. The time, memory, and threads should be tuned according to your application needs and platform capabilities. The provided example uses simplified parameters and should be considered only for demonstration.
• Keep your cryptographic libraries updated. Always use the latest stable releases of cryptographic libraries to ensure you have fixes for known vulnerabilities.

By integrating Argon2 into your password hashing strategy, you significantly improve the security of your application by leveraging one of the leading algorithms designed for this purpose.