Argon2 vs Bcrypt vs Scrypt: Password Hashing Algorithms Compared
Choosing the right password hashing algorithm is critical for protecting user credentials and sensitive data. Here's a detailed comparison of Argon2, Bcrypt, and Scrypt—the three leading algorithms recommended for secure password storage.
Overview
| Feature | Argon2 | Bcrypt | Scrypt |
|---|---|---|---|
| Year Introduced | 2015 | 1999 | 2009 |
| Memory Usage | Configurable | Fixed (~4KB) | Configurable |
| Parallelism | Yes | No | Yes |
| GPU/ASIC Resistance | Very High | Moderate | High |
| Memory Hardness | Yes | No | Yes |
| Implementation Complexity | Medium | Low | Medium |
| Library Support | Growing | Very Wide | Wide |
Algorithm Summaries
Argon2
Background: Winner of the Password Hashing Competition (2015), designed to maximize resistance against brute-force and hardware attacks.
Strengths:
- Highly configurable (memory, time, parallelism)
- Three variants: Argon2d, Argon2i, Argon2id
- Comprehensive resistance to GPU, ASIC, and side-channel attacks
Best For: New systems, high-security applications, environments where memory-hardness is crucial.
Bcrypt
Background: Developed in 1999, based on the Blowfish cipher, and widely used in web applications.
Strengths:
- Adaptive work factor (can increase computational cost as hardware improves)
- Built-in salt for rainbow table resistance
- Simple to implement, very broad support
Limitations: Fixed low memory usage, less resistant to modern hardware attacks compared to Argon2 and Scrypt.
Best For: Legacy systems, applications needing simplicity and wide compatibility.
Scrypt
Background: Created in 2009 for Tarsnap, designed to be memory-hard and resistant to large-scale hardware attacks.
Strengths:
- Configurable CPU and memory cost
- Strong protection against ASIC and GPU attacks
- Used in some cryptocurrencies (e.g., Litecoin)
Limitations: Higher memory usage can be a challenge for resource-constrained environments.
Best For: Systems needing strong hardware attack resistance, cryptocurrency, high-security applications with sufficient memory.
Security and Performance
| Algorithm | Security Highlights | Typical Hash Time | Memory Usage |
|---|---|---|---|
| Argon2 | Most secure, memory-hard, GPU/ASIC resistant | ~150ms | ~64MB (configurable) |
| Bcrypt | Secure, but fixed memory, less GPU resistant | ~250ms | ~4KB |
| Scrypt | Very secure, memory-hard, ASIC resistant | ~200ms | ~32MB (configurable) |
- Argon2 offers the highest level of configurable security and is considered the most future-proof.
- Bcrypt remains secure and reliable but is less adaptable to modern hardware threats.
- Scrypt is highly secure against hardware attacks but uses more memory than Bcrypt.
Implementation Considerations
Argon2
More complex to implement, but flexibility and security make it ideal for new projects.
Bcrypt
Easiest to implement, excellent legacy support, but less flexible.
Scrypt
Offers a balance, but requires careful parameter selection and more resources.
When to Use Each Algorithm
Choose Argon2 if:
- You want the most modern, secure, and flexible password hashing.
- You need resistance to GPU/ASIC and side-channel attacks.
- You are building a new system or can upgrade existing infrastructure.
Choose Bcrypt if:
- You need a proven, simple solution with wide support.
- Your system is legacy or cannot support higher memory usage.
Choose Scrypt if:
- You need strong hardware attack resistance.
- You can allocate more memory for hashing.
- You are working with cryptocurrencies or high-security applications.
Conclusion: For modern applications with adequate resources, Argon2 is the recommended choice due to its superior security and flexibility. However, Bcrypt remains a solid option for systems with limited resources or when wide compatibility is necessary. Scrypt offers a middle ground with strong security features for applications that can handle its memory requirements.