Slashdot Mirror
Online MD5 Cracking Service
toast writes "Did you forget your password but have your /etc/shadow? If so, this site is for you. Submit a MD5 hash and within a few days you'll have an answer. Of course, once Slashdot has its way, you'll have to wait a few years for an answer.. At least now I'll always know what f3789b3c1be47758203f9e8a4d8c6a2a means.."
This is why we use salted, iterated hashing.
hmmmm I would never submit any shadow file, who knows what the admin of the site does with the results! Nick
All joking aside, how much do you want to bet this is the first time the slashdot effect /really/ causes a computer to catch fire due to excessive processor heat?
Objects in the blog are closer then they ap
At least now I'll always know what f3789b3c1be47758203f9e8a4d8c6a2a means..
Processing....
(Three days later)
Processing Complete: Result is 42
It would be cool if it didn't suck.
If you have physical access to your computer...which you should...then of course you could just do it all by hand by booting off of a CD. Why go through all this, unless it's to do something you're not suppose to be doing.
I don't know, what would this be usefull for? Remote admin tasks perhaps?
"Music is everybody's possession. It's only publishers who think that people own it." - John Lennon.
Just send us your:
1. SS#
2. Mother's maiden name
3. Address of the account with the forgotten password
4. ID of the account with the forgotten password
5. MD5 Hash of the forgotten password
Please send all info to The Good Samaritans c/o Nigerian Embassy.
Especially since the only people who should have access to /etc/shadow should be the people with root on the box.
Joe bloggs on his shell account isn't going to be able to get it is he ?
Gentlemen, start your penguins
What is /etc/shadow?
"At the moment we can crack md5 hashes in this character range: a-z;0-9 [8] which means we can break almost all hashes (99.56%) which are created from lowercase plaintext with letters and/or digits up to length of 8 characters." (Emphasis mine)
If your password is under 8 characters and contains only lowercase letters and digits, you deserve to be cracked.
If you use a proper password, then you have nothing to fear from this "service"
because Visual Basic isn't case sensitive?
The More Laws, the less Justice --Marcus Tullius Cicero
All this talk about Hash is making hungry for brownies.
-+-=-+-=-+-=-+-=-+-=-+ *** http://www.mountainfort.com *** +-=-+-=-+-=-+-=-+-=-+-
Just so that its clear, they haven't broken MD5 in the cryptographic sense; they're merely using the fact that the 8 character password space is small enough if you are restricted to lowercase alphabets and numbers (about 3*10^12) to run the whole thing through a brute force search. The nice thing is that they precompute all the plaintext-ciphertext pairs, which means that the actual cracking step is simply a lookup. Lookup can be greatly speeded up if you're looking up lots of things at once, so the /. effect is a very good thing for them, throughput-wise :-)
You are mistaken, sir. A combo that produces the same hash is indeed the right answer.
This is something most people never think about. You actually could have several passwds that work for a given account...anything that hashes to the same thing is a working passwd.
"that's not encryption - it's a new perl script that I'm working on..." - from some Matrix parody
Step 1: Create a service that does something which needs a password hash
Step 2: Get a bunch of bored slashdotters to post their password hashes, and log their IPs
Step 3: Crack the hashes, keep the passwords
Step 4: h4xx0r!
And the l33t shall inherit the 34r7h.
As long as you aren't using passwords that are straight out of the dictionary (this is like 3rd grade people) you should be fine even with something like this being available. I suggest quit using passwords, and use passphrases instead. Someone MD5ing phrases will have to look for months not days.. Change your passphrase like every three months and you'll never have a thing to worry about. The only problem is that md5 has a pretty limited key space and "foo" might equal "TheLastStand" so someone may come up with an equivalent key. Regardless, md5 is designed to keep people from being able to easily come up with these passwords or alter a file it is not designed to keep people off of your computer and it is still much better than crypt. Being able to reverse an md5sum isn't going to get someone on your system that hasn't already got in. Make sure root cannot log on to your box and a user cannot su without being in wheel so if someone does crack the md5 they have no hope of getting any more rights than they already have. Configure a script to run to alert you right away if someone attempts to su but gets canned because of not being in the wheel group. Really stuff unix people should have been doing all along
Remember: Don't Panic!
-Mind
Hence an executable file with a specific MD5 value either is the original or garbage that won't run.
Don't count on it. When you create an executable it is easy to put 17 bytes somewhere, that is really not used for anything. After this has been done just start searching for a combination of those 17 bytes that produce the expected hash. It is very likely that more than one choice will exist. Of course this would take too much time.
It is easier to produce a collision. Create two executables, and instead of the 17 bytes from before just leave 9 unused bytes in each file. Then try all choices for each of the two files, and sort the results to find your collision. 2*256^9 is way smaller than 256^17. Of course even this is still infeasible. But it will be possible in a few (50) years. Using SHA1 is a bit better, but it will only take about 100000 times as much CPU time to find a SHA1 collision as an MD5 collision. Which means the computer to do it will be available about 25 years later than the one to find an MD5 collision (assuming More's law still holds).
Do you care about the security of your wireless mouse?
hey's rule: for every slashdot article about something new and cool there exists at least one posting saying that its been done before.
Well, 36 ^ 8 = 2,821,109,907,456. How long does it take to compute an MD5 Sum?
More to the point, consider "cracking" passwords in this manner:
The NSA has been reported to have ACRES of computer space; their own chip fab and some of the fastest computers in the world.
What if, decades ago, they just dedicated banks of systems to cracking all possible passwords hashed with crypt. Then, a few years later, did the same thing with MD5, SHA-1, and Blowfish -- as each became available.
They store all this stuff in a table, and now getting passwords to most systems is nothing more than a quick table lookup.
Yes, I know the math. However, add in a bit of psychology and statistics.
Most people don't use characters you can't type on a keyboard for a password. VERY few do ALT-nnn or something like that. Most are going to be puire alpha, or alphanumeric. Some will contain special characters.
Meaning, you don't have to exhaust the entire 8-bit character space to get the vast majority of what you're looking for.
Is it really a surprise that something like this is starting to be possible on consumer systems?
Heck, imagine a beowulf cluster dedicated to this...
Learning HOW to think is more important than learning WHAT to think.
If it's a production server that you can't afford to even reboot, maybe you shouldn't be giving the root password to some random website
Yes, because knowing the password means that you automatically know the IP address too, right?
Personally, I think it would be better if they released an app that does this.
Yeah, a 47GB app. That'd be a snap to download.
They're using RainbowCrack - the app is no secret.. it's the data tables that make this useful.
It is a time-memory tradeoff. They come up with a "reduction function" R, which maps hashes into keys. It is not a reversal of the md5 algorithm, it just generates some key based on the hash. Then they create sequences of hash, key, hash, key, hash, key... with each key being the reduction function applied to the previous hash, and each hash being the hash function applied to the previous key. They stop their sequences when they reach "distinguished values," which may e.g. have 0's for the first 12 bits. Then they store the start and endpoints of the sequence.
So now they have a list of start and endpoints for these chains of hashes and keys. To crack a hash, they apply the same process to it - reduction function, hash, reduction function, hash, until they reach a value that is in their table of endpoints. Then they begin at the startpoint associated with that endpoint, and regenerate the sequence up to the hash they're trying to crack. Since the key directly before that hash hashes to that hash, they've successfully cracked the hash.
The "rainbow" refers to the recent innovation of using a different reduction function for each step of the sequence, i.e. using R1 on the first hash, R2 on the second, etc. This means that, even if two sequences contain the same hash, they probably won't be exactly the same after that - a significant problem with the older method of having a single reduction function.
If you want to read about this in more detail with math symbols and such, the pdf is linked from the site.
ROLAND The combination is (hesitates) 827ccb. ;)
HELMET 827ccb.
SANDURZ 827ccb. (writes)
ROLAND 0eea8a.
HELMET 0eea8a.
SANDURZ 0eea8a. (writes)
ROLAND 706c4c.
HELMET 706c4c.
SANDURZ 706c4c (writes)
ROLAND 34a1689.
HELMET 34a1689.
SANDURZ 34a1689. (writes)
ROLAND (hesitates) 1f84e7b.
HELMET 1f84e7b.
SANDURZ 1f84e7b. (writes)
HELMET So the combination is 827ccb0eea8a706c4c34a16891f84e7b (lifts mask) That's the stupidest combination I've ever heard in my life. That's the kinda thing a fucking n00b would have on his Windows box.
Join the TWIT army now!
Same thing for windows users (only different) is here. Submit an LM or NT hash, get the password emailed back to you...
How many Slashdotters does it take to change a light bulb? One to change it, another one to change it again, and then fifty or sixty more to let everyone know the precise date and time of the first changing.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
The "salt" is used to change how the password is hashed. If you look at the shadow password file on your computer, you'll see some lines that look like this
root:$1$abcdefge$abcd1234efg789hijklmno:0:0:...
You'll notice that the password field (the stuff after the 1st colon, and before the 2nd colon) is itself divided into 3 fields separated by dollar signs. The purpose of these fields are:
1st field - Identifies hashing method. This allows for future changes to how the password in stored while allowing backward compatability with existing passwords.
2nd field - This contains the salt used to hash the password. In order to verify a new password, this exact salt must be used in the hashing process. Since in this case, it's 8 characters long and each character can be one of 64 values, it means that each possible password my be hashed into one of 2^48 different values. This salt is generated randomly at the time that you set your password. The randomly generated salt is then stored here for use in verifying future authencation attempts.
3rd field - This is the actual hashed password using the salt specified in the previous field. It is 22 characters long, which with base 64 encoding can store 132 bits. Since MD5 only hashes to 128 bits, there are 4 unused bits at the tail end of this value.