Update BCrypt Hash Rounds for Better Security

[YuKARLO15]

Currently using 10

[YuKARLO15]

Understanding bcrypt Salt Changes in Authentication Systems

You're right to be cautious about changing the salt generation approach in your authentication system. Here's why this matters:

Effects of Changing Salt Parameters

1. No Impact on New Users: Changing the salt generation only affects new password hashes created after the change. New users will get passwords hashed with the new parameters.

2. Existing Users Not Affected: Importantly, existing hashed passwords in your database remain valid. The complete salt information is stored within each hash string itself.

3. No System Breakage: Your system won't break for existing users because:

   • The bcrypt comparison function extracts the salt from the stored hash
   • When a user logs in, it uses their stored hash's embedded salt parameters

If You Want to Upgrade Salt Parameters

If you decide to increase security by changing the work factor (e.g., from 10 to 12):

1. For new users: They'll automatically get the improved security

2. For existing users: Their passwords remain valid with the old work factor

3. Gradual migration: You can rehash existing users' passwords the next time they successfully log in:

   // When user logs in successfully
   if (await bcrypt.compare(password, user.storedHash)) {
     // Check if hash needs upgrade (e.g., if using old work factor)
     if (needsRehash(user.storedHash)) {
       // Generate new hash with updated parameters
       const newHash = await bcrypt.hash(password, 12);
       // Update user's password hash in database
       await updateUserPassword(user.id, newHash);
     }
     // Continue with login success
   }

This gradual approach ensures your system remains secure while avoiding disruption for existing users.