BCrypt: Secure Password Hashing and Best Practices
What is BCrypt?
BCrypt (Blowfish Crypt) is a cryptographic hashing function specifically designed for securely hashing passwords. It is based on the Blowfish cipher and incorporates a built-in salt to protect against rainbow table attacks. BCrypt is widely used in authentication systems, including Spring Security and Django.
Blowfish Cipher Overview
Blowfish is a block cipher that encrypts data in 64-bit blocks using the same key for both encryption and decryption.
Hashing vs. Encryption
- Hashing: Converts data into a fixed-length hash value, ensuring data integrity and secure password storage.
- Encryption: Scrambles data so it can be decrypted back to its original form using a key.
How BCrypt Works
1. Salting
Salting enhances security by adding a random string of characters (salt) to the password before hashing. This ensures:
- Each hash is unique, even for identical passwords.
- Protection against rainbow table attacks.
2. Key Expansion and Iterations
- Key Expansion: Converts the original password into multiple subkeys, making each step of hashing use different values.
- Iterations: The algorithm repeatedly processes the password multiple times, increasing computational effort to slow down brute-force attacks.
3. Adaptive Function
BCrypt includes an adaptive function that allows increasing the cost factor over time as computational power grows, ensuring long-term security.
Understanding Rainbow Table Attacks
A rainbow table attack is a method used by attackers to crack hashed passwords by using precomputed hash values for common passwords.
How Rainbow Tables Work
- Attackers create a massive database of hashed passwords from common password inputs.
- When they obtain a hashed password (e.g., from a data breach), they compare it with their precomputed hashes to find a match.
- If a match is found, they retrieve the original password.
How BCrypt Prevents Rainbow Table Attacks
- Salting: Each password is hashed with a unique random salt, ensuring that even identical passwords have different hashes.
- Slow Hashing: The iterative nature of BCrypt increases the computational effort required, making it impractical for attackers to generate rainbow tables for large numbers of possible passwords.
- Adaptive Cost Factor: As computing power increases, security can be strengthened by increasing the cost factor, further deterring attacks.
Example: Using BCrypt in Java
import org.mindrot.jbcrypt.BCrypt;
public class BCryptExample {
public static void main(String[] args) {
String password = "mySecurePassword";
// Using a cost factor of 10 (default)
String hashedPassword10 = BCrypt.hashpw(password, BCrypt.gensalt(10));
System.out.println("Cost Factor 10: " + hashedPassword10);
// Using a higher cost factor of 12 (stronger security)
String hashedPassword12 = BCrypt.hashpw(password, BCrypt.gensalt(12));
System.out.println("Cost Factor 12: " + hashedPassword12);
}
}
Key Features of BCrypt
- Widely Used: Found in authentication frameworks like Spring Security and Django.
- Built-in Salting: Protects against precomputed attacks (rainbow table attacks).
- Slow Hashing Function: Makes brute-force attacks computationally expensive.
- Adjustable Cost Factor: Enhances security as computing power increases.
Best Practices for Using BCrypt
✔ Use a high cost factor (e.g., 12 or higher for better security).
✔ Never store raw passwords, always store hashed versions.
✔ Use BCrypt.checkpw() for password verification instead of == to prevent timing attacks.
Conclusion
BCrypt is a highly secure and widely used password hashing algorithm. It offers built-in salting, iterative hashing, and adaptability, making it an excellent choice for protecting passwords against brute-force attacks. By preventing rainbow table attacks and allowing security enhancements over time, BCrypt ensures robust password protection for authentication systems.
