1. What is Password Entropy?

Password entropy is a measurement of how unpredictable a password is, expressed in bits. It quantifies the difficulty of guessing or brute-forcing a password based on its length, character variety, and complexity.

2. How Does the Calculator Work?

The calculator uses the password entropy formula:

Where:

• \( Length \) — Number of characters in the password
• \( CharacterSet \) — Number of possible unique characters
• \( ComplexityBonus \) — Additional complexity factors (in bits)

Explanation: The formula calculates how many bits of information are contained in the password, which directly relates to how difficult it is to crack.

3. Importance of Password Entropy

Details: Higher entropy passwords are more secure against brute-force attacks. Modern security guidelines recommend passwords with at least 80 bits of entropy for critical systems.

4. Using the Calculator

Tips: Enter password length (number of characters), character set size (number of possible unique characters), and any additional complexity bonus (in bits). Common character set sizes:

• 26 - lowercase letters only
• 52 - upper and lowercase letters
• 62 - letters and numbers
• 94 - all printable ASCII characters

5. Frequently Asked Questions (FAQ)

Q1: What is a good entropy value for passwords?
A: For most purposes, aim for at least 80 bits. Critical systems should use 128 bits or more.

Q2: How does character set affect entropy?
A: Larger character sets (more possible characters) exponentially increase entropy. Adding special characters significantly improves security.

Q3: What is the complexity bonus?
A: Additional security factors like password composition rules, dictionary checks, or other constraints that make guessing harder.

Q4: Is entropy the only factor in password security?
A: No. Resistance to dictionary attacks, not being reused, and proper storage/handling are also crucial.

Q5: How long would it take to crack a high-entropy password?
A: A password with 128 bits of entropy would take billions of years to crack with current technology.