Password Entropy Explained: Bits and Crack Resistance
What entropy means for passwords, how to calculate it in bits, and why a 60-bit entropy password is practically uncrackable.
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Tags: security, passwords, entropy
Password Entropy: The Math Behind Strong Passwords Password entropy is the single most honest measure of password strength. Unlike rule-based meters that reward character diversity regardless of how predictable the overall password is, entropy measures the actual uncertainty an attacker faces — how many guesses they'd need to try before finding your password. What Entropy Measures In information theory, entropy measures uncertainty. For passwords, it answers: "If an attacker knows everything about how this password was created — the character set, the length, the method — how many guesses do they need on average?" The formula is: H = L × log₂(N) Where: H = entropy in bits L = password length in characters N = size of the character set This formula assumes the password was generated by…
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