Poisonous MD5 – Wolves Among the Sheep
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Poisonous MD5 – Wolves Among the Sheep
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Re: Poisonous MD5 – Wolves Among the Sheep
#2Aren't all hashing algorithms vulnerable to the possibility for collisions (albeit with different degrees of difficulty)? It sounds like the problem here is more related to the logic that relies on a hash alone to make important decisions.
Not saying that MD5 is a good choice in this case, just that we may be blaming the wrong thing.
Re: Poisonous MD5 – Wolves Among the Sheep
#3Aren't all hashing algorithms vulnerable to the possibility for collisions (albeit with different degrees of difficulty)? It sounds like the problem here is more related to the logic that relies on a hash alone to make important decisions. Not saying that MD5 is a good choice in this case, just that we may be blaming the wrong thing.
Yeah, but MD5 is broken in the sense that you can generate a collision on purpose.
Re: Poisonous MD5 – Wolves Among the Sheep
#4Aren't all hashing algorithms vulnerable to the possibility for collisions (albeit with different degrees of difficulty)? It sounds like the problem here is more related to the logic that relies on a hash alone to make important decisions. Not saying that MD5 is a good choice in this case, just that we may be blaming the wrong thing.
The collision-resistance property that all good hashes should have (and md5 lacks) states that an attacker with an input and its hash cannot arbitrarily produce a second input with the same hash. The possibility of it happening in the wild will always exist with hashes by their finite nature, but the only way an attacker should be able to find collisions is by enumerating the input space (rainbow table generation).
Re: Poisonous MD5 – Wolves Among the Sheep
#5Aren't all hashing algorithms vulnerable to the possibility for collisions (albeit with different degrees of difficulty)? It sounds like the problem here is more related to the logic that relies on a hash alone to make important decisions. Not saying that MD5 is a good choice in this case, just that we may be blaming the wrong thing.
Your parenthetical is the key, though. There's a big difference between a hash algorithm where generating a collision requires a few minutes of work on a cheap computer (MD5, now) and a hash algorithm where generating a collision requires a computer the size of the universe operating for a trillion trillion years (any good cryptographically secure hash).
Re: Poisonous MD5 – Wolves Among the Sheep
#6I don't get why it is a security problem that someone can manufacture false positives for an anti-virus. What is the benefit for a virus to have non-malicious code caught by the anti-virus?
False negatives would be more of an issue if the anti-virus has white lists and one can manufacture a Microsoft Excel MD5 signature with a malware. But that's not what the article refers to.
MD5 is only broken if you want to use it as a non-reversible hashing algorithm or if you want to use it as a an unforgeable signature. But it's perfectly fine for many other usage.
Re: Poisonous MD5 – Wolves Among the Sheep
#7Aren't all hashing algorithms vulnerable to the possibility for collisions (albeit with different degrees of difficulty)? It sounds like the problem here is more related to the logic that relies on a hash alone to make important decisions. Not saying that MD5 is a good choice in this case, just that we may be blaming the wrong thing.
Your parenthetical is the key, though. There's a big difference between a hash algorithm where generating a collision requires a few minutes of work on a cheap computer (MD5, now) and a hash algorithm where generating a collision requires a computer the size of the universe operating for a trillion trillion years (any good cryptographically secure hash).
Cool - didn't realize the difference was so great. I've always known that the good algorithms are better because they're more difficult to brute-force, but always wondered if it's just a matter of a few years before the "impossible" becomes possible. Your illustration helps clarify that improbability in my mind - thanks!
Re: Poisonous MD5 – Wolves Among the Sheep
#8Aren't all hashing algorithms vulnerable to the possibility for collisions (albeit with different degrees of difficulty)? It sounds like the problem here is more related to the logic that relies on a hash alone to make important decisions. Not saying that MD5 is a good choice in this case, just that we may be blaming the wrong thing.
Yes, but the complexity of finding a collision in SHA1 is about 2^14 higher than MD5, and even SHA1 is being sunset by many people.
Re: Poisonous MD5 – Wolves Among the Sheep
#9Earlier quoted context omitted.
Your parenthetical is the key, though. There's a big difference between a hash algorithm where generating a collision requires a few minutes of work on a cheap computer (MD5, now) and a hash algorithm where generating a collision requires a computer the size of the universe operating for a trillion trillion years (any good cryptographically secure hash).
Cool - didn't realize the difference was so great. I've always known that the good algorithms are better because they're more difficult to brute-force, but always wondered if it's just a matter of a few years before the "impossible" becomes possible. Your illustration helps clarify that improbability in my mind - thanks!
MD5 is also supposed to require a tremendous amount of computation, it's just that there are weaknesses in the algorithm that were eventually discovered, such that an attacker can short circuit much of that work. The reason that SHA-1 is being sunset is that some preliminary results by researchers suggest that it also has weaknesses that can enable it to be short circuited, and that researchers appear to be on a path to discovering those weaknesses.
Re: Poisonous MD5 – Wolves Among the Sheep
#10Aren't all hashing algorithms vulnerable to the possibility for collisions (albeit with different degrees of difficulty)? It sounds like the problem here is more related to the logic that relies on a hash alone to make important decisions. Not saying that MD5 is a good choice in this case, just that we may be blaming the wrong thing.
Your parenthetical is the key, though. There's a big difference between a hash algorithm where generating a collision requires a few minutes of work on a cheap computer (MD5, now) and a hash algorithm where generating a collision requires a computer the size of the universe operating for a trillion trillion years (any good cryptographically secure hash).
Did breaking MD5 require a computer the size of the universe 20 years ago?