Software decrypting md5 hash password

You can unsubscribe at any time. Please, can anyone help me? MD5 is NOT used to encrypt a text, it is used to convert a text to some obfuscated form. It is a summary of the original text. Hashing is an irreversible process whereas encryption is reversible provided the key used for encryption is available. However, some dictionaries are available which are used to reverse summarize the hash which can be referred to in case a reverse hash of some commonly used text is to be obtained.

If you know the original password, then just hash it with MD5 and check against the stored MD5 hash. If they are identical you have the password, right? This will allow you to encrypt as well as decrypt. You cannot decrypt MD5, but you can compare outputs since if you put the same string in encrypt method it will have the same crypted output.

Right, MD5 is only one way for encryption. No Account? Sign up. By signing in, you agree to our Terms of Use and Privacy Policy. I said generally because, if you know for example that you are looking for a string of ASCII characters, and it's less than, say, 12 bytes, it is probable that there is only one input that produces a given output. But there are always going to be collisions infinite , and unless you have some external constraint like in my example you will never know which is right — Adam Batkin.

This can be done using after-the-fact probabilities rather than prechosen constraints. It obviously can't be done in general, but it is still quite useful.

Show 5 more comments. MD5 is a bad hash to use for passwords: It's fast, which means if you have a "target" hash, it's cheap to try lots of passwords and see whether you can find one which hashes to that target.

Salting doesn't help with that scenario, but it helps to make it more expensive to try to find a password matching any one of multiple hashes using different salts. I believe it has known flaws which make it easier to find collisions, although finding collisions within printable text rather than arbitrary binary data would at least be harder.

Jon Skeet Jon Skeet 1. Yes, there are other methods, but you need to understand what Jon said above - 'you shouldn't email them their password - that's sensitive information which might remain sensitive.

A password should stay as secure as possible - usually by keeping it as a hash only in a database. And also the fact that if the password can be reversed, that means anyone who gets access to your database can get at users' passwords. Not a good idea. One way passwords should be the norm; only keep the real password even encrypted if you absolutely have to e. I've seen antispam-measures where the receivers webserver denies an incoming mail just to wait for the sender's mailserver to retry spambots usually only try once.

That could easily exceed your 10 minute timeout. There's no guarantee that it's the original plaintext value. If the password is unknown, you can't know whether the one revealed is the original one or not.

But the point is that one way hashes like MD5 by definition lose information. The fact that sites like this can come up with a matching password is just good evidence of MD5 being a bad algorithm to use for security reasons. Show 7 more comments. Chris Huang-Leaver 5, 6 6 gold badges 38 38 silver badges 66 66 bronze badges.

Daniel May Daniel May 8, 1 1 gold badge 31 31 silver badges 43 43 bronze badges. I've got a few nitpicks. Rainbow tables are not brute forcing. There are actually programs and sites that do brute force very simple passwords of a few characters generally they just loop over a few hours or days, and you can fill in a hash and hope it comes up in the loop.

And unfortunately, given the lack of quality of many passwords, the chance that one pops up is not "a very small chance". I have to interject: Reversing MD5 is not malicious by nature. How you use this ability is what determines malice or good intent.

If some one figured out how to reverse it and shared that with the world, they could win a nobel prize or something. That is how we all get better. But if you find a reverse to MD5 and then use it for personal gain, then yes, you are being malicious. Add a comment. I would add that finding another value that hashes to the same output is called a "collision".

This is the most common method of breaking MD5-hashed systems. Renesis, finding data that hashes to a previously known value is called a "preimage", actually, and it's much, much harder than just a collision. No preimage attack has yet been demonstrated against MD5, but collision attacks have been used. The point of hash functions when used for password storage is not that there are lots of possible passwords which give the same hash there are, but most of them are longer than the hash itself , but that it is hard to find even one of them which would be enough to access the system.

And yes, because of rainbow tables you don't use unsalted hashes. To be technical, you can't perform MD5 with certainty, because the hardware might have malfunctioned. In the same way, you may not be able to be certain that the password was password rather than all the other infinite inputs that produce the same hash but which all look quite random, but you can be close enough. The pigeonhole principle applies of course, but it is still computationally infeasible to find a second input that hashes to a certain value, e.

If you find an X that hashes to a given H X then you can be certain that X is the correct input. This makes the whole first section of this answer and most of the rest incorrect. Not possible, at least not in a reasonable amount of time. Matthew Groves Matthew Groves If the hash wasn't salted, you'd be surprised how often all it takes is a google search for the hashed value Not really practical for a password retrieval system though, even an unsalted one : — Matthew Groves.

You can't revert a md5 password. Nettogrof Nettogrof 2, 2 2 gold badges 15 15 silver badges 22 22 bronze badges. Nix the rainbow table idea. If you're salting -- and you should be -- then it wouldn't work, anyhow.

StevenSudit If they are still using MD5 to hash passwords instead of using a strong password hash, then you cannot assume they are using a salt. Maybe they do, probably they don't. No, he must have been confused about the MD5 dictionaries. Robert Greiner Robert Greiner Sinan Taifour Sinan Taifour 9, 3 3 gold badges 29 29 silver badges 29 29 bronze badges. MD5 is a hashing algorithm, you can not revert the hash value.

Svetlozar Angelov Svetlozar Angelov Bill the Lizard Bill the Lizard k gold badges silver badges bronze badges. Dinah Dinah If a match is found then it is certain that it will be the original password. If this wasn't the case then it would be possible to generate collisions given any H X where X is an message without a predefined structure determined by the adversary. It is computationally infeasible to find such a collision for a cryptographically secure hash function, even if it is a broken hash function such as MD5.

MaartenBodewes: "If a match is found then it is certain that it will be the original password. I'd say it's extremely likely to be the original password, but it doesn't have to be.

The fact that there are more possible passwords than MD5 hashes mean it must be possible for there to be two passwords with the same hash. Just because it's computationally infeasible to find such collisions doesn't mean they don't exist.

Or have I misunderstood you? JonSkeet If it is computationally infeasible to find a collision on purpose then finding one by chance is equally unlikely or worse. And this doesn't even consider that the message probably needs to be small and have a specific format to be considered a password. MaartenBodewes: But there's a big difference between "astronomically unlikely" and "impossible".

Your statement about it being certain that it's the right password is overly strong, IMO. That suggests a mathematical certainty that isn't present. It is "just" extremely unlikely. Cryptography relies on these kind of odds. That it is theoretically possible to find another input message is nice, but for this question on StackOverflow there is no need to consider it.

And rainbow tables are only filled with possible passwords. They won't contain enough data there to be ever even a chance of a collision they would either unknowingly overwrite the mapping or become famous.

You cannot un-hash an MD5 hash. Ned Batchelder Ned Batchelder k 69 69 gold badges silver badges bronze badges. By design, all same-length hashes suffer from collisions.

It's unavoidable when restraining variable-length data. MD5 is considered obsolete for its rate of collisions, not for the fact of colliding. MD5 is considered broken because of the proven possibility of constructing inputs that collide. Kage Kage 1 1 gold badge 3 3 silver badges 9 9 bronze badges. There is nothing much wrong with this answer except that the speed of the hash function is very much a problem because most passwords are not secure enough and allow an adversary to perform a dictionary attack.

For that reason slow password hash functions are used instead of fast cryptographically secure hash functions. You can find online tools that use a dictionary to retrieve the original message.

In some cases, the dictionary method might just be useless: if the message is hashed using a SALT message if the message is hash more than once For example, here is one MD5 decrypter online tool. Rainbow tables - not dictionary attacks - are useless if a salt is used. Hashing more than once - without a salt - still allows rainbow tables, although finding a pre-existing one online is certainly less likely.

Maarten Bodewes Maarten Bodewes NB: seven years later, oh well hopefully someone will find it useful. Thanks for the reply. However I'm going to "1 up" you : I can't remember if I actually did this, but in theory it should work. Instead of waiting for every single user to login so that we can re-encrypt their password, you can simply encrypt the hashed version of their password.

So every password will be MD5 hashed, and then encrypted. Just updated the password check to do the same and the user data should be safe without requiring user intervention.

But for the moment you just have to remember that there is an infinite possibility of input for a finite output possibilities always 32 characters. We have a giant database of known MD5 hash, so we can find the result for a lot of hash. The MD5 algorithm is very fast. So, you can use it where you want, without slowing down your website. And so to validate them, you can encrypt the input password, and check it with the database one.

The first step is to create a user account. To do this, you need to create a database, with at least two fields: username and password. The password will be MD5 encrypted, so it will always be 32 characters length.

You probably already done that, you just need to use the md5 function to encrypt the password. In the login process, you need to compare the input password to the database password.