Understanding Bcrypt Rounds: Balancing Security and Performance

When it comes to securing user passwords, using a strong hashing algorithm is crucial. One of the most popular and reliable hashing algorithms is bcrypt. Bcrypt is designed to be slow and computationally expensive, making it resistant to brute-force attacks. In this blog post, we'll dive into the concept of rounds in bcrypt and understand how they impact security and performance.

What are Bcrypt Rounds?

Bcrypt uses a parameter called "rounds" to determine the computational cost and time required to calculate the hash. The number of rounds is exponential, meaning that each additional round doubles the amount of work required to compute the hash. This exponential increase in work makes it significantly more difficult for attackers to crack passwords using brute-force techniques.

Default Rounds in Bcrypt

When bcrypt was first introduced, the recommended number of rounds was 12. However, as computing power has advanced over time, the recommended number of rounds has been adjusted upwards to maintain a sufficient level of security. In normal practice, the default number of rounds used by the bcrypt hashing algorithm is 10. However, this can be adjusted based on the specific implementation and security requirements.

Here are a few examples of commonly used rounds in bcrypt:

• PHP's default implementation of bcrypt uses 10 rounds.
• Python's bcrypt library uses 12 rounds by default.
• Node.js's bcrypt library uses 10 rounds by default.

Balancing Security and Performance

While increasing the number of rounds enhances security by making it harder to crack passwords, it also comes with a performance trade-off. The more rounds used, the longer it takes to hash passwords. This increased hashing time can impact the overall performance of the system, especially when dealing with a large number of password hashing operations.

Therefore, when choosing the number of rounds, it's essential to strike a balance between security and acceptable performance based on the specific requirements of the application. As a general guideline, it is recommended to choose a number of rounds that takes approximately 250ms to 500ms to compute on the server hardware used in the production environment. This provides a good balance between security and usability.

Conclusion

Bcrypt is a powerful hashing algorithm that helps protect user passwords from brute-force attacks. The number of rounds used in bcrypt determines the computational cost and time required to calculate the hash, directly impacting security and performance. While higher rounds offer enhanced security, it's crucial to find the right balance that aligns with the application's requirements and ensures an acceptable user experience.

When implementing bcrypt in your application, consider the specific security needs and performance constraints. Choose a number of rounds that provides strong protection against attacks while maintaining reasonable hashing times. Regularly review and adjust the number of rounds as computing power evolves to ensure ongoing security.

By understanding and properly utilising bcrypt rounds, you can build a robust password hashing system that safeguards user credentials and maintains the integrity of your application.