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A Really Good Article on How Easy it Is to Crack Passwords

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Re: A Really Good Article on How Easy it Is to Crack Passwords

#51

Post by enscr »

derefr wrote: post #6
salmonellaeater wrote: post #4

> "This is an answer to the batteryhorsestaple thing." Steube misunderstands the xkcd comic [1]. There's a really good comment which explains it: "It could be argued that Randall's example of 4 words is too short -- and indeed, for some applications, it is. However for a typical dictionary size, and genuinely random selection, it is massively stronger than "typical" passwords and in fact easily adequte to defeat the…

What password length would you need to get away with a plain-old grammatical english sentence (i.e. very much non-random selection)? For example: "and in the swept plains of winter's vale, our hero did beseech the emperor to send for his forces" -- what would be the difficulty in cracking that, given that this isn't a quote from a book or anything, but just a sentence that popped into my mind and seems easy enough to…

My God, are you going to type all of that or will you need a script to do it for you. Watch out for those touch-screen thingies people are touting around.

Re: A Really Good Article on How Easy it Is to Crack Passwords

#52

Post by corin_ »

'Also included in the list: "all of the lights" (yes, spaces are allowed on many sites), "i hate hackers," "allineedislove," "ilovemySister31," "iloveyousomuch," "Philippians4:13," "Philippians4:6-7," and "qeadzcwrsfxv1331." "gonefishing1125" was another password Steube saw appear on his computer screen. Seconds after it was cracked, he noted, "You won't ever find it using brute force."'

If you won't ever find "gonefishing1125" using brute force, how on earth did they find "qeadzcwrstxv1331"?

Re: A Really Good Article on How Easy it Is to Crack Passwords

#53

Post by danielweber »

raverbashing wrote: post #39
cperciva wrote: post #2

Remember, security against cracking is a combination of password strength and key derivation function strength . Nothing will save you if your password is "password". Not much will save you if your password is hashed with MD5. But scrypt can be over 100,000,000 time stronger than MD5 -- so if you're using scrypt you can afford to use a password which is 100,000,000 times weaker. "jdtwbv" hashed using scrypt is strong…

""jdtwbv" hashed using scrypt is stronger than "H.*W8Jz&r3" hashed using MD5" Is it? I'm not sure. for the first one you're using lowercase letters (and digits, I'm giving you that 'free') For the first one we have 36^6 For the second one (all printables) 100^9 Relation between them: ~ 459,393,658. If you're saying scrypt is 100M times better, in this case the second one is safer And the relation is important but les…

People have built huge rainbow tables of MD5 hashes.

I don't really keep up with that game (like WoW, it seems like a fun game, but only if you are willing to put in a lot of your time), but I think the current limit is somewhere around 8 or 9 characters if you are pulling from all printables, meaning that "H.*W8Jz&r3" with MD5 is probably not breakable right now.

Take off two characters, or wait 3 years, and it probably will be.

Re: A Really Good Article on How Easy it Is to Crack Passwords

#54

Post by danielweber »

derefr wrote: post #6
salmonellaeater wrote: post #4

> "This is an answer to the batteryhorsestaple thing." Steube misunderstands the xkcd comic [1]. There's a really good comment which explains it: "It could be argued that Randall's example of 4 words is too short -- and indeed, for some applications, it is. However for a typical dictionary size, and genuinely random selection, it is massively stronger than "typical" passwords and in fact easily adequte to defeat the…

What password length would you need to get away with a plain-old grammatical english sentence (i.e. very much non-random selection)? For example: "and in the swept plains of winter's vale, our hero did beseech the emperor to send for his forces" -- what would be the difficulty in cracking that, given that this isn't a quote from a book or anything, but just a sentence that popped into my mind and seems easy enough to…

Almost 20 years ago I saw a great password-picking article that still holds today. http://world.std.com/~reinhold/diceware.html

Take a list of 6^5 words. Roll 5 dice. Take that word from the list. Do this 4 more times. You now have a five-word passphrase like "moire fraud 80 row bernet".

Even if someone knew the exact method and list you did to get that passphrase, there are 28430288029929701376 combinations, giving you over 64 bits of entropy.

Someone has probably tried to rainbow table all those results for MD5. If a core can do 1 billion hashes per second, it would take 900 core-years to build a complete list of all those combinations, which is probably feasible for a small group to put together, but messing with the list just a little bit or adding a 6th word would likely put you past that even for a crappy MD5 hashing.

Re: A Really Good Article on How Easy it Is to Crack Passwords

#56

Post by kamjam »

enscr wrote: post #51
derefr wrote: post #6

Earlier quoted context omitted.

What password length would you need to get away with a plain-old grammatical english sentence (i.e. very much non-random selection)? For example: "and in the swept plains of winter's vale, our hero did beseech the emperor to send for his forces" -- what would be the difficulty in cracking that, given that this isn't a quote from a book or anything, but just a sentence that popped into my mind and seems easy enough to…

My God, are you going to type all of that or will you need a script to do it for you. Watch out for those touch-screen thingies people are touting around.

http://keepass.info/

Some things you don't always need to use from those touch-screen thingies

Re: A Really Good Article on How Easy it Is to Crack Passwords

#57

Post by cperciva »

raverbashing wrote: post #39
cperciva wrote: post #2

Remember, security against cracking is a combination of password strength and key derivation function strength . Nothing will save you if your password is "password". Not much will save you if your password is hashed with MD5. But scrypt can be over 100,000,000 time stronger than MD5 -- so if you're using scrypt you can afford to use a password which is 100,000,000 times weaker. "jdtwbv" hashed using scrypt is strong…

""jdtwbv" hashed using scrypt is stronger than "H.*W8Jz&r3" hashed using MD5" Is it? I'm not sure. for the first one you're using lowercase letters (and digits, I'm giving you that 'free') For the first one we have 36^6 For the second one (all printables) 100^9 Relation between them: ~ 459,393,658. If you're saying scrypt is 100M times better, in this case the second one is safer And the relation is important but les…

If you're saying scrypt is 100M times better

Oops, you're right, I got the math wrong when I looked at the table in my paper. I should have said that scrypt can be over 100,000,000,000 times stronger. ;-)

Re: A Really Good Article on How Easy it Is to Crack Passwords

#58

Post by rypskar »

tsahyt wrote: post #7
dublinclontarf wrote: post #3

Earlier quoted context omitted.

Just use bcrypt :-p

bcrypt is not bad and you're definitely better off with that than with MD5, but scrypt performs better for these sort of things. There was an article on HN a week or so ago about this.

I think that since bcrypt is more available I will continue recommending it, and using anything else should be based on a risk assessment. I do not think peoples that don’t do risk assessment on storing password will care enough to spend time on something that is not easy to set up when it “only” affect security

Re: A Really Good Article on How Easy it Is to Crack Passwords

#59

Post by barrkel »

corin_ wrote: post #52

' Also included in the list: "all of the lights" (yes, spaces are allowed on many sites), "i hate hackers," "allineedislove," "ilovemySister31," "iloveyousomuch," "Philippians4:13," "Philippians4:6-7," and "qeadzcwrsfxv1331." "gonefishing1125" was another password Steube saw appear on his computer screen. Seconds after it was cracked, he noted, "You won't ever find it using brute force." ' If you won't ever find "gon…

Have you looked at the keyboard pattern for qeadzcwrsfxv1331?

I imagine there are a whole bunch of these geometric patterns, and different combos of them are tried.

Re: A Really Good Article on How Easy it Is to Crack Passwords

#60

Post by barrkel »

dasil003 wrote: post #44
belorn wrote: post #24

Earlier quoted context omitted.

The algorithm is not targeted against the type of password which the XKCD comic suggests. The algorithm is designed to exploit common human behavior, which is similar to the XKCD method but not identical. The significant difference is that human behavior in picking words is not random, while the XKCD method requires the word selection process to be truly random. The "iloveyousomuch" example by Steube is unlikely to b…

Where are you guys getting this? All I read was this: > Steube was able to crack "momof3g8kids" because he had "momof3g" in his 111 million dict and "8kids" in a smaller dict. > "The combinator attack got it! It's cool," he said. Then referring to the oft-cited xkcd comic, he added: "This is an answer to the batteryhorsestaple thing." It sounds to me like he's combining words randomly, not "exploiting common human be…

He found a password by 2 words randomly from two dictionaries of different sizes, so he only had m * n combinations to choose from, and his n is a lot smaller than m.

Whereas the xkcd approach is more like m * m * m * m.

In other words, exponentiation > multiplication.

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