![]() So what IS the “Search Space Calculator” ? And no password cracker would wait 17.33 centuries before checking to see whether “Password” is the magic phrase. Yet the Search Space Calculator above shows the time to search for those two passwords online (assuming a very fast online rate of 1,000 guesses per second) as 18.52 minutes and 17.33 centuries respectively! If “123456” is the first password that's guessed, that wouldn't take 18.52 minutes. The #1 most commonly used password is “123456”, and the 4th most common is “Password.” So any password attacker and cracker would try those two passwords immediately. Since it could be easily confused for one, it is very important for you to understand what it is, and what it isn't: IMPORTANT!!! What this calculator is NOT. Simplicity and power of the “ Password Haystacks” concept. The prestigious “ Consumer Reports” has also picked up on the (The Haystack Calculator has been viewed 8,726,146 times since its publication.) Limited to, at most, a few hundred guesses per second. Note that typical attacks will be online password guessing Los Angeles' KABC-TV produced a terrific & succinct twoĪnd a half minute explanation of the Password HaystacksĬoncept: Click this link to view their quick introduction. ![]() The Password Haystack Concept in 150 Seconds So, to activate the cool calculator below, you must ENABLE the JavaScript interpreter built into your web browser. With JavaScript, everything stays in your browser where it belongs and is never sent anywhere for any purpose. If your test passwords were sent back to GRC for server-side analysis, it would not only be much slower and more cumbersome, but also inherently open to privacy questioning. While we have bent over backwards to make GRC's many other site features completely functional without any client-side JavaScript (mostly to thumb our nose at the rest of the world to show that it can be done) the highly interactive nature of this page really screams out for a JavaScript solution.īut also, performing this page's calculations with client-side JavaScript is the only way to provide you with privacy. You'll never be able to look at a bitstream without knowing the distribution and say "there are X bits of entropy here.(Because we DON'T have JavaScript)If you are reading this, your browser's built-in JavaScript interpreter is disabled and is thus (not surprisingly) unable to interpret JavaScript. But you'll never be able to say any more than "it looks pretty uniformly distributed to me!". You can do statistical tests, like you mention, to verify that the output "looks random" (from a certain perspective). If you're using a hardware RNG, then you need to know the probabilities associated with the data it gives you, else you cannot formally find the Shannon entropy (though you could give it a lower bound if you know the probabilities of some, but not all, events).īut note that in any case, you are dependent on the knowledge of the distribution associated with the byte stream. ![]() Recall that a deterministic algorithm cannot add entropy to an input, only take it away, so the entropy of all inputs to a deterministic algorithm is the maximum entropy possible in the output. So, to find how much entropy is present in a byte stream, you need to know how the byte stream is generated and the entropy of any inputs (in the case of PRNGs). Thus, $F$ has exactly one bit of entropy, what we expected. There are two events, heads and tails, each with probability $0.5$. So what is the entropy in a single flip of a coin? Let $F$ be a random variable representing such. Note that the definition is a function of a random variable (i.e., a distribution), not a particular value! Let $X$ be a random variable that takes on the values $x_1,x_2,x_3,\dots,x_n$. Here is the definition of Shannon entropy. ![]() If I give you the bits 1011, that could have anywhere from 0 to 4 bits of entropy you have no way of knowing that value. That is, the process used to generate a byte stream is what has entropy, not the byte stream itself. ![]() Entropy is a function of the distribution. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |