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Password Entropy Calculator

Try this password entropy calculator to check the strength of your password in bits of entropy.

Password Entropy Calculator

Let us understand the concept of password entropy in detail by exploring its importance in cyber security. Also learn how to calculate password entropy based on various important factors to check password strength.

What is Password Entropy?

Password entropy is a measure of the randomness and unpredictability of a password. It is expressed in bits and quantifies how difficult it is to crack a password through guessing or brute-force attacks.

Importance of Password Entropy

The importance of password entropy lies in its direct correlation with password strength. Higher entropy generally indicates a stronger password. Weak passwords with low entropy are susceptible to various attacks, while strong passwords with high entropy provide better security. It helps defend against brute force attacks, dictionary attacks, and other password cracking techniques.

Important Factors

The two most important factors affecting the entropy of a password are:

1. Character Set

The size of the character set used in a password greatly influences its entropy. For example, if the password only uses lowercase letters, the character set size is 26. If it uses both lowercase and uppercase letters, the size is 52, and so on. Adding numbers and symbols increases the size of the character set.

2. Password Length

Password length has a significant impact on entropy. Longer passwords generally have higher entropy because there are more possible combinations of characters.

Calculate Password Entropy

The formula to calculate entropy is:

Entropy = log2(Character Set SizePassword Length)

In this formula, log2 represents the logarithm base 2. The result is the number of bits of entropy. Essentially, this calculation tells you the number of binary digits (bits) needed to represent all possible combinations of the characters in the password.

For example, a password with 8 characters using only lowercase letters (26 possible characters) would have an entropy of:

Entropy = log2(268) ≈ 37.6 bits

In real-world scenarios, passwords typically balance between usability and security. Entropy in the range of 40-80 bits is common, with higher values for more sensitive applications. Systems might enforce minimum entropy requirements to ensure a basic level of security, but there's often a practical upper limit based on usability and system constraints.

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