MD5 - Not as safe as once believed

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And just for your sake, hash algorithms and public key encryption algorithms are essentially the same thing.

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I rest my case. The statement was not intended to be insulting but to allow interested parties to pursue information on the topic which is based on the facts and the research involved as opposed to listening to people who think hash functions and public/private key encryption are the same thing. *sigh* If you want to know the difference, click on my little profile and go find one of the many messages I have posted pertaining to encryption, and read some of Tim_Axes while you're at it, you might learn something which is why you said you're here. As for the MD5 attack, people have been aware of flaws in it for years and knew that it would be broken eventually jut like MD 1-4. The attack used the Biham/Chen technique to find a collision. This means two seperate pieces of input produced the same piece of output. Is this bad? Yes. Is this a diasaster? Not really. All hash functions have collisions the idea being that its just really,really hard to find them. Using the Biham/Chen method made it easy enough to discover one. This is not the same as a preimage attack which would have far more people worried. A collison attack does not allow you to create the hash of your choosing. You have to use the hash the collison that is found, and. Like Tim_axe was demonstrating the biggest problem with this is with signed code/and signatures. It could allow some one to get one piece of code signed and the substitute it for the other, IF they had the collision, but this isnt really realated to passwords. If someone has your password file of MD5 hashes, they arent going to look for a collision. They're going to run a dictionary attack on it and crack the **** out it. You'll have the whole list cracked before you find a collision on one password. My point is no one should have your password file in the first place, and if your relying on MD5 or some other hash function to protect you from a weak password you are SOL. Faster ways of finding the collisions will be found, of that I have no doubt. But hopefully by then people will be using another function for signing like SHA1 (which will also be broken, of that I also have no doubt) this is the nature of cyrpto. You make something, you break it. You make something better. Repeat.


-Maestr0

Oops. My bad. I guess that statement was misleading.

What I meant was that they both rely on the concept of a one way algorithm, albeit, yes, the mathematics of each are entirely different.

Really, what I was trying to say was that IMHO a good hash algorithm is as good as a good encryption algroithm, if it's all you need.

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Originally posted here by Maestr0
They're going to run a dictionary attack on it and crack the **** out it. You'll have the whole list cracked before you find a collision on one password.
-Maestr0

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Well actually, what they find might be a password collision rather than the actual password... it would be quite a bummer if a complicated 30 character, alpha-numeric and special character password had a collision with a 5 character dictionary word [okay it might be unlikely but get the point].

From the point of view of the attacker they don't care what they find, be it password or collision, as long as the hash matches.

But I agree entirely that nobody should get access to the files that are password-related.

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Originally posted here by Striek
And does that make you smarter because you were, in your own insignifigant opinion, able to realize that?

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He makes a good point though, if you actually do read the research material it kinda refutes what you, TH, and others (somewhat including myself) have been saying... I got the chance to read it through, and now I understand it better.

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What difference does it make if I don't know what I'm talking about?

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LMAO! Thanks for the sig material man!

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That's why I come here. If I post anything incorrectly, I would hope that somebody points out my error. If everyone knew what they were talking about, nobody would come here.

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That's not necessarily true, but if you only see that one set of motivations, you probably aren't open to knowing about others.

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BTW, Horsey has already forgotten more than you will ever know in this matter. The fact that you can quote a few historacal and Googleable facts in a discussion forum proves nothing. Telling us all that we know nothing also proves nothing except the fact that you somehow believe that you can make that judgement.

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Mmmmhmmm... TH, is your ass sore from all the kissing it's been receiving lately?

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And just for your sake, hash algorithms and public key encryption algorithms are essentially the same thing. They're what peope call one way algorithms, meaning that in both cases, one cannot compute the original input (i.e. the original message or the prime factors of a private key) if one knows only the output (i.e. the digest or the public key).

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BWAHAHAHAHAHA!

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What difference does it make if I don't know what I'm talking about?

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Just FYI, Public Key encryption and hashing are way different. In the case of the former, you actually use it to encrypt data, and the public key you give out describes how to DECRYPT the data, to obtain a copy. Hashing is to Encryption as eating breakfast is to working in a cereal packing plant....

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I am aware that I know nothing. That's why I'm here. My education is nothing but the continued discovery of my own ignorance.

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Then why argue with someone who obviously has a bit more experience and knowledge than you do? This isn't the third grade, TH doesn't need people to "pick his side". If he has responses he will surely provide them, and I highly doubt anyone is going to lose any sleep over a disagreement on a web forum (but then again these days you never know).

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Originally posted here by Soda_Popinsky If it were possible, wouldn't it be seen in a rainbow table? I wonder how big the biggest rainbow table is...

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It should show up, yes. If I'm able to pick up my dual 100GBs I'm going to try generating some of the smaller rainbow tables for MD5 and see if there are any collisions, mostly because rainbow tables and hash collisions have been a matter of passing interest for me for a few months now.

/begin male pissing contest -- round 3

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Then why argue with someone who obviously has a bit more experience and knowledge than you do?

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Because arguing can be fun sometimes.

In reference to hashing and encryption being the same thing, I was referring to the process of computing a public key from the private and vice versa, not computing the ciphertext. It just came out all wrong. Hence my previous post.

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Hash functions are NOT encryption fucntions

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What I was trying to say was the similarity between the two is in the fact that calculating a private key from a public key can be somewhat likened to calculating a message from the digest. It's a very rough comparison, I know.

I wasn't trying to kiss ass, either. I was merely trying to dispute the fact that

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Tim_Axe is the only person in this thread who appears to know WTF he's talking about

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, which I took to mean "You're all idiots." Apparently, that was not his intent.

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That's why I come here. If I post anything incorrectly, I would hope that somebody points out my error. If everyone knew what they were talking about, nobody would come here.

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Should read

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That's why I come here. If I post anything incorrectly, I would hope that somebody points out my error. If everyone knew what they were talking about all the time, nobody would come here.

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Granted, many peeople come here for the community and to share what they know, but how much fun (and admit it, the ego boost wouldn't be as good either) would it be if you couldn't say anything that somebody didn't know?

My whole point with MD5 being compromised is that despite the fact that the technical ramifications are small, the legal ones are enormous. It's just smarter migrate to a better algorithm now, rather than face an argument like this if you use MD5 to verify evidence integrity.

/end round 3

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Hashing is to Encryption as eating breakfast is to working in a cereal packing plant....

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lol, nice analogy. I'll have to use it to describe the difference for my not as geeky as me friends.

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Originally posted here by Striek
Because arguing can be fun sometimes.

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It's a rare thing when someone so freely explains they were trolling.

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In reference to hashing and encryption being the same thing, I was referring to the process of computing a public key from the private and vice versa, not computing the ciphertext. It just came out all wrong. Hence my previous post.What I was trying to say was the similarity between the two is in the fact that calculating a private key from a public key can be somewhat likened to calculating a message from the digest. It's a very rough comparison, I know.

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You're still very incorrect. A hash is a reproducible set of bit values based on the contents of a given piece of data. A public key is a specific sequence of bits that act as directions for encrypting data. It is generated from the private key. It is not based on the data in the private key strictly speaking; it is generated from the private key in a fashion which ensures only the private key can read the data the public key encrypts.
The fundamental difference: hashes are based on the data they are created from, public keys are not necessarily based on the data in the private key -- which is I might add a security measure. If you have no data from the private key to work from, you would have to bruteforce every combination of bits in the key length. As 1024bit keys would have 1.79[...]e+308 (1.79 * 10^308) possible combinations, it would take a long while to bruteforce.

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I wasn't trying to kiss ass, either. I was merely trying to dispute the fact that, which I took to mean "You're all idiots." Apparently, that was not his intent.

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As I said, I think TH can speak for himself. In fact, I know he can.

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Granted, many peeople come here for the community and to share what they know, but how much fun (and admit it, the ego boost wouldn't be as good either) would it be if you couldn't say anything that somebody didn't know?

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I come here purely for debate, information exchange, and to poke fun at people who employ the use of their fingers without first engaging their brain (or eyes, or google for that matter). I don't consider it an ego trip to disseminate information, or help someone fix a problem. It's a small ego trip to laugh at people who write first and research second, but I consider the ego stroking to be outshadowed by the sheer entertainment value.

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Originally posted here by Maestr0
P.S. Tim_Axe is the only person in this thread who appears to know WTF he's talking about,


-Maestr0

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Where did I say anything in this thread that was incorrect?

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Where did I say anything in this thread that was incorrect?

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You said that Blowfish is better at everything... what about Rijndael? Both Rijndael and Twofish (Blowfish's sucessor) were running in the NIST competition for AES standard, and Rijndael won... someone definitely disagrees with you :p

That's more of an opinion isn't it?