Password Strength - XKCD

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A webcomic of romance, sarcasm, math, and language. Special 10th anniversary edition of WHAT IF?—revised and annotated with brand-new illustrations and answers to important questions you never thought to ask—out now. Order it here! Password Strength

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Permanent link to this comic: https://xkcd.com/936/ Image URL (for hotlinking/embedding): https://imgs.xkcd.com/comics/password_strength.png ((The comic illustrates the relative strength of passwords assuming basic knowledge of the system used to generate them. A set of boxes is used to indicate how many bits of entropy a section of the password provides. The comic is laid out with 6 panels arranged in a 3x2 grid. On each row, the first panel explains the breakdown of a password, the second panel shows how long it would take for a computer to guess, and the third panel provides an example scene showing someone trying to remember the password.)) [[The password "Tr0ub4dor&3" is shown in the centre of the panel. A line from each annotation indicates the word section the comment applies to.]] Uncommon (non-gibberish) base word [[Highlighting the base word - 16 bits of entropy.]] Caps? [[Highlighting the first letter - 1 bit of entropy.]] Common Substitutions [[Highlighting the letters 'a' (substituted by '4') and both 'o's (the first of which is substituted by '0') - 3 bits of entropy.]] Punctuation [[Highlighting the symbol appended to the word - 4 bits of entropy.]] Numeral [[Highlighting the number appended to the word - 3 bits of entropy.]] Order unknown [[Highlighting the appended characters - 1 bit of entropy.]] (You can add a few more bits to account for the fact that this is only one of a few common formats.) ~28 bits of entropy 2^28 = 3 days at 1000 guesses sec (Plausible attack on a weak remote web service. Yes, cracking a stolen hash is faster, but it's not what the average user should worry about.) Difficulty to guess: Easy. [[A person stands scratching their head trying to remember the password.]] Person: Was it trombone? No, Troubador. And one of the Os was a zero? Person: And there was some symbol... Difficulty to remember: Hard. [[The passphrase "correct horse battery staple" is shown in the centre of the panel.]] Four random common words {{Each word has 11 bits of entropy.}} ~44 bits of entropy. 2^44 = 550 years at 1000 guesses sec Difficulty to guess: Hard. [[A person is thinking, in their thought bubble a horse is standing to one side talking to an off-screen observer. An arrow points to a staple attached to the side of a battery.]] Horse: That's a battery staple. Observer: Correct! Difficulty to remember: You've already memorized it ((The caption below the comic reads: Through 20 years of effort, we've successfully trained everyone to use passwords that are hard for humans to remember, but easy for computers to guess.)) {{Title text: To anyone who understands information theory and security and is in an infuriating argument with someone who does not (possibly involving mixed case), I sincerely apologize.}} RSS Feed - Atom Feed - Email Comics I enjoy: Three Word Phrase, SMBC, Dinosaur Comics, Oglaf (nsfw), A Softer World, Buttersafe, Perry Bible Fellowship, Questionable Content, Buttercup Festival, Homestuck, Junior Scientist Power Hour Other things: Tips on technology and government, Climate FAQ, Katharine Hayhoe xkcd.com is best viewed with Netscape Navigator 4.0 or below on a Pentium 3±1 emulated in Javascript on an Apple IIGSat a screen resolution of 1024x1. Please enable your ad blockers, disable high-heat drying, and remove your devicefrom Airplane Mode and set it to Boat Mode. For security reasons, please leave caps lock on while browsing.

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