![]() ![]() In general, the more characters a password has and the more diverse the set of characters it includes, the higher its entropy will be. It is a way of quantifying how difficult it would be for an attacker to guess or crack the password. By storing a password strength score for each user account in the system I can build several different metrics to show overall system weakness and make a case for stronger passwords. Password entropy is a measure of the strength of a password or passphrase. When I am working on legacy systems where users have extremely weak passwords I have to have some concrete evidence of that weakness before I can make a case for forcing all users to change their passwords to a new (enforced) strong password. ![]() The strength of a password is a function of length, complexity, and unpredictability. In its usual form, it estimates how many trials an attacker who does not have direct access to the password would need, on average, to guess it correctly. In making a comment I realized that I can better explain the usefulness of this calculation. Password strength is a measure of the effectiveness of a password against guessing or brute-force attacks. I could really use a code example (even if not strictly in PHP) to get me going. I have seen some mention of logarithmic equations to calculate said entropy, but I have yet to see a good example that isn't actually written as a mathematical equation. I do welcome suggestions for other approaches though. Contains the results of an entropy calculation. I will probably have to work in another algorithm or two for dictionary attacks, l33t replacement passwords, etc-but I do feel that entropy will play an important role in such an 'overall' system rating. What constitutes a strong password By the simplest definition, the strength of a password is an indicator of the. Contains structs and methods for calculating estimated time needed to crack a given password. The second part of this question is: how useful will this number really be? My end goal is to generate a 'score' for each password in the system that we can use to monitor our overall system security as a dynamic entity. ![]() I will be using the password entropy as just one part of a larger security system and as a way to analyze our overall data security based on information accessible if a user's password is compromised and how easily a password may be broken by brute force. Related Calculators Frequently change your passwords, if possible after every few days, particularly whenever there is suspicion that it may have been. A lot of folks on the net have their own home-baked weighting algorithm, but I am really looking for the scientific answer to the equation. I have been unable to find any code examples that are empirically sound and would really like some help in finding the 'right' way to calculate a final number. First, dealing with calculating the entropy of a password in PHP. Then, we calculate the effective length of the password to ensure the next rules: some orderliness decreases total entropy, so 1234 is weaker password. ![]()
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