Argon2 Hash Tool

Argon2 is the winner of the Password Hashing Competition (2015) and is currently recommended by security experts as the most secure password hashing algorithm. It's designed to be memory-hard, making it extremely resistant to GPU and ASIC attacks. Unlike bcrypt or PBKDF2, Argon2 requires significant memory to compute hashes, which makes brute-force attacks exponentially more expensive and impractical.

Argon2i is optimized to resist side-channel attacks (timing attacks) and is best for password hashing. Argon2d is optimized to resist GPU cracking attacks and is better for cryptocurrencies. Argon2id is a hybrid that combines both approaches and is recommended for most use cases, including password hashing. It provides resistance against both side-channel and GPU attacks.

Memory cost (in KiB) determines how much RAM the algorithm uses - higher values make attacks more expensive. Time cost is the number of iterations the algorithm performs - higher values increase computation time. Parallelism is the number of parallel threads - it can improve performance on multi-core systems but doesn't significantly affect security. Our server enforces reasonable limits to prevent resource exhaustion.

For most applications, the default settings (Argon2id with 64 MiB memory, 3 iterations, 1 thread) provide excellent security. If you need higher security, increase memory cost first (to 128 MiB), then time cost. Test the performance on your target hardware - hash generation should take 0.5-1 second on typical server hardware. Remember that higher values improve security but increase computation time and resource usage.

Yes! Argon2 hashes encode all parameters (variant, memory cost, time cost, parallelism, and salt) within the hash itself. When verifying, the algorithm automatically extracts these parameters from the hash, so you don't need to specify them. This makes Argon2 hashes self-contained and portable across different systems and implementations.

While this tool uses secure server-side processing, we recommend using it only for testing and development purposes. For production applications, implement Argon2 directly in your server code using libraries like argon2 (Node.js), argon2-cffi (Python), or equivalent in your programming language. Never transmit real user passwords to online tools.

Argon2 is superior to both bcrypt and PBKDF2 in terms of security. While bcrypt is still secure, it uses less memory (4 KB) compared to Argon2 (configurable up to 128+ MiB), making it more vulnerable to GPU attacks. PBKDF2 is even less memory-intensive and faster to compute. Argon2's memory-hardness makes attacks significantly more expensive, providing better protection against modern hardware-accelerated attacks.

Like bcrypt, Argon2 automatically generates a unique random salt for each hash. This is a critical security feature that prevents rainbow table attacks and makes each hash unique, even for identical passwords. The salt is included in the hash output, so verification works correctly. This behavior is intentional and enhances security.

Yes, you can gradually migrate from bcrypt to Argon2. The typical approach is to verify passwords against the existing bcrypt hash, and if successful, generate a new Argon2 hash and replace the old one. This way, users are migrated to the more secure algorithm when they next log in. You can't convert bcrypt hashes directly to Argon2 without the original password.

Argon2 hashes follow the PHC (Password Hashing Competition) string format: $argon2id$v=19$m=65536,t=3,p=1$[salt]$[hash]. This format includes the variant (argon2id), version (19), parameters (memory=65536 KiB, time=3, parallelism=1), salt (base64-encoded), and the hash itself (base64-encoded). All information needed for verification is contained in this string.

Argon2 hashing time depends on the parameters you choose. With default settings (64 MiB memory, 3 iterations), it typically takes 0.5-1 second on modern server hardware. This is intentional - password hashing should be slow enough to deter brute-force attacks but fast enough to not impact user experience during login. Higher parameters will increase the time proportionally.

While Argon2 was specifically designed for password hashing, the Argon2d variant can be used for other purposes like key derivation in cryptocurrencies or proof-of-work systems. However, for general-purpose hashing (like file integrity or digital signatures), use standard cryptographic hash functions like SHA-256 or SHA-3 instead. Argon2 is optimized for slow, memory-intensive operations specific to password protection.