Using Google To Crack MD5 Passwords

stern writes "A security researcher at Cambridge was trying to figure out the password used by somebody who had hacked his Web site. He tried running a dictionary through the encryption hash function; no dice. Then he pasted the hacker's encrypted password into Google, and voila — there was his answer. Conclusion? Use no password that any other human being has ever used, or is ever likely to use, for any purpose. I think."

Comments

Salt

[porneL]

No, the conclusion is you should always use salted hashes.

Re:Salt

[eln]

I agree. Also, fry them in bacon fat and add pepper.

Re:Salt

[Anonymous Coward]

No, the conclusion is you should always use salted hashes. I agree, but this isn't something the user can do. I can't register for a site and say, "I need to remember to use salt!" The site has to implement it and implement it correctly.

The guy posting was posting from the perspective of the user, not the author of the system. The conclusion from the summary is still accurate since you can't make the assumption that salt is always used. The next best defense is a crazy fucking password.

Re:Salt

[eldavojohn]

And blackjack ... and hookers. In fact, forget the hashes!

Re:Salt

[SevenDigitUID]

That's not true. The user can generate a string with something like dd if=/dev/urandom bs=21 count=1|openssl base64 , store that string, and append it the the true password each time the log in. This has exactly the same results as the site correctly implementing salting. So what you are saying is the best defense is to use a crazy fucking password?

Re:Salt

[Anonymous brave dude]

Use a crazy fucking password, but you don't have to remember all of it.

Re:Salt

[Em Adespoton]

agree, but this isn't something the user can do. I can't register for a site and say, "I need to remember to use salt!" The site has to implement it and implement it correctly.

The guy posting was posting from the perspective of the user, not the author of the system. The conclusion from the summary is still accurate since you can't make the assumption that salt is always used. The next best defense is a crazy fucking password.

This is why my passwords are themselves salted hashes. The likelihood of someone else using my passwords is the same as a regular hash collision, I get to use a separate password for each place one is required, and the hashing mechanism and salt are simple enough for me to keep in my head. End result: infinite number of easily generatable and retrievable passwords that look just like a hashed password when decoded.

Re:Salt

[Sangui5]

Rainbow tables? Salting breaks it.
Precomupted dictionaries? Salting breaks it.
Brute force and compare against the whole pw list? Salting breaks it.

Salting is your friend. Long salts don't cost much, but make many attacks completely infeasible. Unix has been using salted passwords since forever. Yet nthash *still* doesn't include a salt.

Re:Salt

[networkBoy]

Not entirely.
That adds a "local salt" but... courtesy of possible hash collisions there is another password that may work equally well.
by having the login function add the salt a straight rainbow lookup is defeated (unless you pre-computed a rainbow with the salt). As admin he could still enter the salted MD5, find a suitable password without salt, disable salting, get in enable salting, change the password. BUT a "normal" hacker without access to the DB tools and salting function of the app, but in possession of the hash table (and even the salt to some extent) would be defeated. if the attacker had the salt and hash table then with enough time the will break you login through rainbow tables, but not before.
-nB

Re:Salt

[Anonymous Coward]

Ice building up on your sidewalk? Salting breaks it.

Re:Salt

[AKAImBatman]

Better solution:

http://passwordmaker.sourceforge.net/passwordmaker.html

One password for all sites, but a unqiue, "fscking crazy" password for all of them. You're welcome.

Re:Salt

[Jarjarthejedi]

Pretzels missing that unique flail? Salting solves it!
Need something else to put on those fries? Salt it!
Need to make your friend's drink taste awful? Salt is the way to go.

(Somewhere along the line we left the analogy department :P)

Re:Salt

[Garridan]

Because if somebody gets that file, they've got your password. This way, they'll have to hack your brain, as well as your computer, to get at your password.

Re:Salt

[maxwell demon]

This is slashdot, we need a bad car analogy too. :P Your car rusting too slowly? Salt solves that! :-)

Re:Salt

[csteinle]

When a problem comes along, you must salt it.
Before the cream sits out too long, you must salt it.
When something's going wrong, you must salt it.

Now salt it! Salt it good!

Re:Salt

[Sangui5]

You're implying that salting on UNIX makes attacking the hash infeasible, this is simply not true.
Salting doesn't make breaking hashes infeasible, but it makes the attacker work harder, and makes certain highly efficient attacks infeasible.

There are only 4096 different combinations in the salting algorithm in crypt() will use which a brute forcer can easily iterate.
And I completely agree that 12 bits of salt is insufficient in a modern world. Which is why MacOS 10.4 and up uses 32 bits of salt, most Linux implementations use 48 bits of salt, and OpenBSD uses (a rather paranoid) 128 bits. Since it doesn't require any more effort from the user, and only a tiny amount of resources, there's no reason not to use a large salt.

Salting a known algorithm is almost pointless because as I just described salted passwords can be just as easily defeated if you know the mechanism
If you have the password hashes they you have the salt too. Either way, brute forcing one password is no harder. But it means you have to work harder to do a whole list of passwords, because each password has to be attacked individually.

Salting also makes precomputation (pre-built dictionaries and rainbow tables) infeasible. Every bit of salt in essence doubles the amount of storage for your precomputation attack. This is (partly) why a fairly effective set of rainbow tables for LANMAN hashes take only 500ish MB, NTLM hashes take 8.5 GB, but even for the old Unix crypt() it would take at least 2 TB. And don't even think about trying any precomputation attacks against OpenBSD; even if the user was stupid and restricted themselves to 5 digit alphanumeric passwords, your rainbow table would consume more storage than exists. Salting makes you attack each password individually, and keeps you from doing any work ahead of time.

this is why NT doesn't include salt.
NTLM doesn't include a salt because (1) MS is trying to maintain a semblance of backwards compatibility with some ill-designed challenge response authentication mechanisms, and (2) they haven't learned the lesson that salting is a valuable strategy to make attacking hashes more difficult.

Also salt was used on UNIX only because when shadow passwords didn't exist the system had to be protected against users that had the same password and could easily read the password file to compare.
That is one reason why salts were used for old Unix crypt(). The other was to make precomputed dictionary attacks harder, which is still a valid use. Today, the best reason to use a salted hash is to avoid rainbow tables.

Really, the modern reason to use a salt is to prevent the type of attack the original poster used, and to prevent rainbow table attacks. Both of these are good attack techniques, and salting completely moots them.

Re:Salt

[Sangui5]

You are correct that salting does not prevent nor make harder a brute force attack against one password.

It *does* breaks the Google attack, a precomputed dictionary, and rainbow tables, *even* if the attacker just wants *your* password.

Of these, rainbow tables is by far the most effective. Nobody computes their own rainbow tables. If I want to attack your hashed password, I'll download or buy a set of rainbow tables. Salting prevents this, because every salt value needs its own set of rainbow tables (or you have to include the salt rainbow table entries, which is approximately the same). Either way, using a 32-bit salt implies that to be equally effective, the total set of tables has to be 4 billion times larger. A 128 bit salt; well, you just can't create a set of rainbow tables for that. It just demolishes their effectiveness.

As you imply, there is a variant on salting which even makes plain brute forcing harder: don't store all of the salt. Of course this is (1) not widely deployed, and (2) imposes a high cost for legitimate use. Anyway, using repeated hash iterations is better, since you can't parallelize it.

MD5 Lookup Site & Names

[eldavojohn]

For those of you who missed it in the article, the has was:

20f1aeb7819d7858684c898d1e98c1bb And sure enough, if you read the comments to the blog, there is a site called http://md5.rednoize.com/ that reveals that the hash is "Anthony." So although Google helped, there appears to be resources online for it (if you don't have your own Rainbow Table mega database).

He could have discovered this if he had used a database complete with names, something I don't think would have been too difficult for him.

This Google search idea is kind of moot if the user uses some very basic password construction such as what I've commented on before. Also, as the blog mentions, this discussion is worthless if WordPress used salting which is related to nonces used in security engineering. I think that stuff has been around for, what about five years now? Wake up WordPress!

Re:MD5 Lookup Site & Names

[PFAK]

He can't be much of a "security researcher" if someone hacked his own website.

Re:MD5 Lookup Site & Names

[joNDoty]

Crap. From their "about" page:

Additionaly everytime when you enter a non-md5 hash string into the search field, the md5 result for that search strings gets stored in our database for future use. Thanks for warning me. I tested to see if my password was in there... it is now!!!

Re:MD5 Lookup Site & Names

[Cairnarvon]

He didn't write the WordPress software, and presumably doesn't have the time to audit every bit of code it uses.
I doubt Bruce Schneier himself audited the entire Movable Type codebase, which he uses for his blog. Does that make Schneier "not much of a security researcher"?

Obligatory

[Anonymous Coward]

In Soviet Amerika, MD5 passwords crack you.

Re:Obligatory

[CrazyJim1]

What about the flip side: Using Crack to Google MD5 passwords?

I wouldn't be too alarmed.

[morgan_greywolf]

Most MD5 password hashes, such as those used in *nix, are salted, and hence secure from this sort of vulnerability. That Wordpress uses unsalted MD5 sums to store passwords boggles my mind. It shows that the developers know even less about cryptography than I do. That's scary.

Re:I wouldn't be too alarmed.

[SevenDigitUID]

That is totally unfair to the wordpress developers. Just because they don't care doesn't mean they don't understand.

Re:I wouldn't be too alarmed.

[cstdenis]

You do realize that most businesses (and therefore most websites you have accounts on) just store passwords plain text because it's easier to do tech support that way. Salted hashes are better than unsalted hashes, but most don't bother hashing at all.

Re:I wouldn't be too alarmed.

[nuzak]

That Wordpress uses unsalted MD5 sums to store passwords boggles my mind. It shows that the developers know even less about cryptography than I do. That's scary.

Oh it's even better than that. It stores your md5 password in a plain text cookie, and if it receives such a cookie, sets an $already_md5 flag to true that's then passed to wp_login() which then just compares it literally against the unsalted md5 entry.

<guinness>Brilliant!</guinness>

Dark Helmet

[Nate Fox]

So the combination is 827ccb0eea8a706c4c34a16891f84e7b. (lifts mask) That's the stupidest combination I've ever heard in my life. That's the kinda thing an idiot would have on his luggage.

Let me guess

[GroeFaZ]

The password was hunter2?

Re:Let me guess

[omnipresentbob]

What's with all the stars in your post?

5 years?

[Junta]

Try decades! The good old days of Unix even had salts (even if they were just two bytes)

In itself nothing new

[owlstead]

But if I ever need to run a hash against a password database, I'll remember this lesson and first perform a Google search. Saves a lot of time and CPU cycles.

I am already doing this for telephone calls I cannot place. If it's an institution or a person that is calling because of profession, the chances that the telephone is listed somewhere on a (search engine) accessible web page is *very* large.

Re:RTFA

[eln]

You're correct. You have totally invalidated the points I brought up in my post. Good show.

My uneducated respose would be:

[newr00tic]

What about the flip side: Using Crack to Google MD5 passwords? 2343e9f361fea282776586d7056025db

Been there. Done that.

[this great guy]

I have personally been using Google this way for a while. This is the first thing I do when I encounter a passwd hash during a pentest. This is a technique that works very well especially for hashes produced by random apps that you have no idea what hashing algorithm they use. It works well not because the public passwd hash databases indexed by Google are large (they are not), but because they are very diverse, both in term of number of algorithms (MD5(), MD5(uppercase()), SHA1(), etc) and in terms of number of hash formats (hexadecimal value, decimal value, base64, etc).

And above all, it only takes 2 sec to perform the Google search.

on a related note...

[sootman]

... I wish Google would collect/show/use checksums of files in search results. It would be a great way to find identical files.* Thousands of uses:

• I found this file on my computer and I forgot where it came from.
  
• I downloaded this file but I forget where I got it. It's too big to email so I would like to send a friend a link to the original file.
• I want to see if anyone has taken this pic from my site and posted it elsewhere.
• This download is taking FOREVER. Is anyone else hosting this exact file?

and many, many more. I had this idea years ago and sent it in to them but haven't heard anything since. I don't want any credit**, just implement it and let me know when it's up and running! And the funny thing is, I'm sure Google is already checksumming every file as part of how they do all their magic. All they have to do is post the data!

* and, since collisions are possible, it would provide a nice corpus to study collisions, etc. in the real world.

** this isn't an entirely original idea. Linux distros have been posting checksums for years as a way to let users verify that their downloads were not corrupted; as a bonus, I (and I'm sure some others) have done searches of those values to find sites hosting that particular release.

Man, I need to change my password NOW.

[fo0bar]

Results 1 - 10 of about 101,000 for d41d8cd98f00b204e9800998ecf8427e. (0.04 seconds)

Credibility?

[MarkLewis]

Am I the only one who thinks that a "security researcher" whose site gets hacked and is about as credible as an accountant who fails an audit?

And for his sake I really hope that he knew about rainbow tables and just decided for some indecipherable reason not to mention that they are far more effective for password cracking than Google searches.

And who submitted this story to Slashdot with the sensational summary about "any password used by anybody, ever" being vulnerable to Google searches? That's an easy enough claim to completely debunk by taking MD5 hashes of several passwords and sampling which ones come back. Let's see:

92259762923b4e79d2073ecb03217462 (hash for 'july2007') - Nothing
6e933f3054f533c63dd59479ca9f4b6f (hash for 'hello_world') - Nothing
2c6c8ab6ba8b9c98a1939450eb4089ed (hash for 'abc123') - Google found this one as an md5 example
6a51f1fe97bdebece7652842a0e2351e (hash for 'pickles') - Nothing
5eaaf94141c371ce96675aa6445003c4 (hash for 'happy') - Nothing

So basically not even common words get picked up by Google, much less "any password used by anybody else, ever".

Re:Credibility?

[dgym]

Your strings have newlines in them, maybe you meant:
echo -n happy | md5sum

most password fields don't accept newlines, so trying without them:
3e652df0f1332cfc9df779d49667defc - still nothing
99b1ff8f11781541f7f89f9bd41c4a17 - still nothing
e99a18c428cb38d5f260853678922e03 - abc123
fd03204cfdc557b0f0d134773ae6fff5 - obscure, it finds a flash app on a site called pickles and things
56ab24c15b72a457069c5ea42fcfc640 - happy

So it is still not that much of a problem, but at least happy is on the list.
I wonder if negative outlook words are more or less secure?

Re:Credibility?

[neonsignal]

I looked these up on google, and they directed me to some slashdot page...

How about "don't use your first name As your PW"?

[nobodyman]

No, the conclusion is you should always use salted hashes.

That's good advice for application developers, but the original post was offering advice to users. Still, even that is a bit of an overreaction. From TFA:

And indeed, the MD5 hash of "Anthony" was the database entry for the attacker. I had discovered his password.

Not to diminish this admin's accomplishment (it sounds like he's quite clever), but doesn't this boil down to "don't use your name as your password"? Or better yet, "don't use any proper name as a password".

Keep in mind that this was a hash of a userid (not a password) that was captured in a google index, and it's highly unlikely that someone will choose a userid on a google-indexed site that just-so-happens to be your 10+ character password that has mixed-case and special characters. I think the same "good password advice" still applies, even in a google-world.

Re:french bitch

[maxwell demon]

I just hate douche bags who can't spell. Spelling errors can make your password more secure!

No worse than Subversion

[Antique Geekmeister]

It's no worse than Subversion's insistence on storing user passwords for any protocol but SSH public keys in a local plaintext file.

Do not *EVER* allow a Subversion system to use the same passwords as the user system, and if you have access to the user's accounts, run a check of their stored Subversion passwords to make sure they didn't use their same password somewhere else as for their local user account.

Re:Salt.. .so then develop

[davidsyes]

a rad ass custom mod chip that the user injects into the cerebral cortex and obdulla loongggatta and up down undah. The user then develops Tourettes Syndrome out the ass and has shit for brains now and only has to utter some crazy fucking ass phrase to seed a crazy fucking password in the solid-state gene-erator cuz they've gone fucking goddam crazy over that motherfuckin' chip in their ass and brain.

Crazy fucking luser. Crazy fucking assword. Crazy fuckin' whirled up world.

The above is the 1.0 tourettes pack, silver. Stainless-fucking-steel adds an additional language pack...