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Original author: 
Casey Johnston

Few Internet frustrations are so familiar as the password restriction. After creating a few (dozen) logins for all our Web presences, the use of symbols, mixed cases, and numbers seems less like a security measure and more like a torture device when it comes to remembering a complex password on a little-used site. But at least that variety of characters keeps you safe, right? As it turns out, there is some contrary research that supports both how frustrating these restrictions are and suggests it’s possible that the positive effect of complexity rules on security may not be as great as long length requirements.

Let's preface this with a reminder: the conventional wisdom is that complexity trumps length every time, and this notion is overwhelmingly true. Every security expert will tell you that “Supercalifragilistic” is less secure than “gj7B!!!bhrdc.” Few password creation schemes will render any password uncrackable, but in general, length does less to guard against crackability than complexity.

A password is not immune from cracking simply by virtue of being long—44,991 passwords recovered from a dump of LinkedIn hashes last year were 16 characters or more. The research we describe below refers specifically to the effects of restrictions placed by administrators on password construction on their crackability. By no means does it suggest that a long password is, by default, more secure than a complex one.

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Original author: 
Dan Goodin


Thanks to the XKCD comic, every password cracking word list in the world probably has correcthorsebatterystaple in it already.

Aurich Lawson

In March, readers followed along as Nate Anderson, Ars deputy editor and a self-admitted newbie to password cracking, downloaded a list of more than 16,000 cryptographically hashed passcodes. Within a few hours, he deciphered almost half of them. The moral of the story: if a reporter with zero training in the ancient art of password cracking can achieve such results, imagine what more seasoned attackers can do.

Imagine no more. We asked three cracking experts to attack the same list Anderson targeted and recount the results in all their color and technical detail Iron Chef style. The results, to say the least, were eye opening because they show how quickly even long passwords with letters, numbers, and symbols can be discovered.

The list contained 16,449 passwords converted into hashes using the MD5 cryptographic hash function. Security-conscious websites never store passwords in plaintext. Instead, they work only with these so-called one-way hashes, which are incapable of being mathematically converted back into the letters, numbers, and symbols originally chosen by the user. In the event of a security breach that exposes the password data, an attacker still must painstakingly guess the plaintext for each hash—for instance, they must guess that "5f4dcc3b5aa765d61d8327deb882cf99" and "7c6a180b36896a0a8c02787eeafb0e4c" are the MD5 hashes for "password" and "password1" respectively. (For more details on password hashing, see the earlier Ars feature "Why passwords have never been weaker—and crackers have never been stronger.")

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Original author: 
Casey Johnston


Why are there so many password restrictions to navigate? Characters want to be free.

Daremoshiranai

The password creation process on different websites can be a bit like visiting foreign countries with unfamiliar social customs. This one requires eight characters; that one lets you have up to 64. This one allows letters and numbers only; that one allows hyphens. This one allows underscores; that one allows @#$&%, but not ^*()[]!—and heaven forbid you try to put a period in there. Sometimes passwords must have a number and at least one capital letter, but no, don’t start the password with the number—what do you think this is, Lord of the Flies?

You can’t get very far on any site today without making a password-protected account for it. Using the same password for everything is bad practice, so new emphasis has emerged on passwords that are easy to remember. Sentences or phrases of even very simple words have surfaced as a practical approach to this problem. As Thomas Baekdal wrote back in 2007, a password that’s just a series of words can be “both highly secure and user-friendly.” But this scheme, as well as other password design tropes like using symbols for complexity, does not pass muster at many sites that specify an upper limit for password length.

Most sites seem to have their own particular password bugaboos, but it’s rarely, if ever, clear why we can’t create passwords as long or short or as varied or simple as we want. (Well, the argument against short and simple is concrete, but the others are not immediately clear). Regardless of the password generation scheme, there can be a problem with it: a multi-word passphrase is too long and has no symbols; a gibberish password is too short, and what’s the % doing in there?

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