decrypt md5 Solved/Closed

Question

Comment déchiffrer un texte chiffré par la méthode md5 en PHP ?   Omen

Bobinours · Accepted Answer

MD5 is a non-reversible algorithm. To use this kind of function, you need to compare 2 strings encrypted with MD5 and see if they are equal. You can then infer the original string.   -= Bobinours =-

jisisv · Answer

Decrypting MD5 makes no sense. The MD5 signature is a value that summarizes the content of a string using a complex algorithm, so that changing just one of these characters will produce a value very different from the original MD5 hash. For example, the MD5 hash of the content of an ISO image of a CD can often be found on FTP servers. This ensures (after using the correct command: md5sum on Linux, md5 on FreeBSD for instance) that the uploaded content matches that present on the FTP site and that there have been no transfer errors).  Decrypting MD is a moot point.  Johan Daine  Gates gave us the windows. Linux gave us the whole house....

jisisv · Answer

Erratum: It should read "downloaded content" and MD5, of course...  Gates gave us the windows. Linux gave us the whole house....

sebsauvage · Answer

jisisv and Boninours are right.  Note that if you have a few million years ahead of you, you can find the file corresponding to an MD5...  :-D

kZn.13 · Answer

We answer him and he completely loses interest in the subject... not even a thank you! France is beautiful, it's beautiful...

Octopuce · Answer

It takes an enormous amount of time to decrypt MD5, but it exists and it can be done, GRID COMPUTING at its peak :)

sebsauvage · Answer

No.  Once and for all: It is impossible  to decrypt  MD5 for the simple reason that it is not  a symmetric algorithm. Therefore, you cannot reverse the transformation.   The only thing you can do is try all possible combinations of characters, calculate their MD5, and compare.  Even with grid computing, it is beyond the capabilities of current computing, except for very short passwords (less than 8 characters).  As for the famous "rainbow tables," you can easily protect against them by adding a salt to the data to be hashed. ( md5('coucou-je-suis-un-salt'+data) instead of md5(data), and your rainbow table is good to throw in the trash. )

slide · Answer

Of course it is possible to decrypt an MD5 hash.
There are two ways to do it: by using ready-made software
- for example: john the ripper for Linux and Unix, https://www.openwall.com/john/
- or ophcrack for Windows, https://ophcrack.sourceforge.io/

Or by performing rainbow table attacks, brute force (or dictionary attacks) or even by salting (which is essentially organized brute force). If you want to learn more about this, I strongly recommend the security portal on Wikipedia.

This is of course to test security

but in no case is a hash meant to be "hashed"

but know that MD5 has been obsolete for a long time (since SHA-512 has been released).

Agent Blue · Answer

I get up and I confirm!  "De-hashing" MD5 makes sense. It all depends on the work and/or research one is doing.  And yes, yes, yes, it is totally possible to "de-hash" MD5...  A great man said: "What one man has built, another man can unbuild..." and I believe this applies to everything...

Agent Blue · Answer

I also wanted to say…

According to the designers of the thing: an average of 87 years to "crack" a 10-character password

Just a few hours for one with less than 6 characters

We are far from the millions of years that some think...

lami20j · Answer

Hello,  A great man said: "What one man has built, another man can tear down..."  And, did this great man ask if the reverse is also true?! ;-) --  lami20j

Agent Blue · Answer

Hey hey! But this is more philosophy than computer science!  That comment is interesting! Generally speaking, we need to view our obstacles objectively. After studying hard, we eventually end up...

sebsauvage · Answer

Several hours for one of less than 6 characters. We are far from millions of years as some think...  Except that any programmer who is somewhat aware of these things will add a salt before hashing (a little salt before hashing... I like the culinary metaphor), which makes this kind of attack completely ineffective. Unfortunately, a certain number of widely used programs (like WordPress) do not use a salt and store the MD5 as is, which makes them dangerous.  If we summarize the 2 most common attacks:  - Brute force: We can easily protect against it by programming a banning system (for example fail2ban or denyhosts for ssh servers).  - Rainbow tables: we add a salt before hashing, which completely invalidates this attack.   So when used properly, no problem continuing to use MD5 or SHA-1.  But be careful with software that you haven't programmed yourself. If you have the source code, add a salt.

Agent Blue · Answer

Totally agree with you Sebsauvage! Thank you for clarifying.   It is impossible to decrypt MD5 for the simple reason that it is not a symmetric algorithm.   It's just that one sentence that had troubled me... But with your latest response that complements it, I'm totally on board!

blux · Answer

And yes, yes, yes, it's totally possible to "de-hash" MD5...  We don't 'de-hash' MD5; at best, we find a sequence that has the same MD5 as the one sought...  --  Catch you later, Blux  "Fools dare to do anything. That's how you recognize them."

Agent Blue · Answer

It was a way of speaking, hence the quotation marks...

VanVan · Answer

If you want to decrypt MD5, you can go to this site, which surely has the largest database on the internet: http://decrypt.vanvan.cc

fiddy · Answer

Hi,  It is impossible to decrypt MD5. It is a message digest algorithm. Mathematically, it is a one-way function. However, through brute force, it is possible to find a valid candidate, meaning one with the same hash, without having certainty that it is the correct one. Can we really talk about decryption in that case? Prefer the term brute-forcing or cracking instead.  We can say that MD5 is cracked the day it becomes possible to find the original message (or one with the same message digest) regardless of the hash. And that day is not near. Even though there are methods to create collisions, they are not currently dangerous since they do not concern a specific digest.  MD5 still has a few good days ahead of it, even if it is not the most recommended today. --  Google is your friend

lol · Answer

lol

hazertyck · Answer

https://www.frameip.com/decrypter-dechiffrer-cracker-hash-md5/

For me, this one doesn’t say it decrypts, but that it cracks, if that makes you happy we're glad... and that way we have our answer.

Now, this is not a rumor: MD5 cannot be decrypted, otherwise it wouldn’t be used in PHP (among others) or in .htaccess for security!

arth · Answer

At the same time, you generally need to know how to obtain the hashed password, and if you have neither access to the machine nor to the file/database containing the hashed password, it will take you a bit longer.  Before wanting to desperately crack a password, it might be wise to know how to obtain it first... --  The wolf, solitary and mysterious.

Anthony · Answer

MD5 is decryptable (much to my surprise)  On authsecu.com, they must have a special algorithm, I don't know...  The link:  https://www.frameip.com/decrypter-dechiffrer-cracker-hash-md5/  (it's also the second Google result when typing "decrypt md5")

thomas · Answer

Hello....  01d460356c9182889cd2eaaab1668065 ( is this an md5? )  7C7-E04-D-D7C510442374-5EA05DAC9F05B ( and this is the hash? )  and especially, once and for all, is it or is it not possible to decrypt either one and know the word that is hidden behind?  I forgot, I have my conscience to myself, and you have yours... all in respect, thank you :)  so, let's avoid the debate, this isn't good, that isn't good.... I have good reasons to want to do it and frankly, I'm just asking for help and not sermons :)

fiddy · Answer

01d460356c9182889cd2eaaab1668065 ( is this md5? ) Apparently yes.  7C7-E04-D-D7C510442374-5EA05DAC9F05B ( and is this the hash? ) The hash of what? In any case, there are no dashes in a hash.  and above all, once and for all, is it or is it not possible to decrypt either one and know the word that is hidden behind it? That's what we've repeated throughout the post. No, it's not possible, it's an irreversible function. After that, it is possible to brute-force it or use dictionary attacks or rainbow tables. But if the message is complex enough, the brute force will take too much time and the dictionary attack or rainbow tables will fail.  so, let's avoid the debate, this is not good or that is not good....I have good reasons for wanting to do it and frankly, I’m just asking for help and not sermons :) I see no good legal reason to do it ;). --  Google is your friend.

fiddy · Answer

You are mixing concepts. You should not confuse encryption functions and hashing functions.  the encryptor...is acting up...and yet this program is supposed to decrypt.... Here, we are talking about MD5, which is a hashing function. It has nothing to do with an encryption function. The principle of a hashing function is to provide a digest from which you cannot retrieve its predecessor. The encryption function ensures the confidentiality of a message while allowing it to be decrypted if you know the key.  So to conclude, a hashing function is irreversible. And if the message is robust, you will not be able to retrieve the message from its hash. Otherwise, the hash loses its purpose. --  Google est votre ami

loupius · Answer

Well, this is really a topic that interests a lot of people: cracking the secret of a password or a text... I'm not like fiddy, a specialist, but I have a few basic notions of combinatorial analysis. So, what is md5: it’s 128 bits that is obtained from a string of characters (understood in the broad sense, a text of 100...000 characters is a string of characters). Here’s why, regardless of the reliability of the md5 hash, it is almost impossible to be sure of the original string. 128 bits -> 2^128 which is only 3.4 * 10^38 possibilities. For a text made up of 72 possible characters (26 uppercase, 26 lowercase, 10 digits, and 10 punctuations); if the text is: - 10 characters -> 72^10 which is 3.4 * 10^18 possibilities (10^18 = 1 quintillion = 1 billion of billions). - 20 characters -> 72^20 which is 1.4 * 10^37 possibilities; we can consider (assuming no duplicates) that each string may correspond to an md5 'code', - 21 characters -> 72^21 which is 1 * 10^39 possibilities, there are necessarily duplicates.... thus impossibility of being sure of the original message. - 1000 characters (about half a page) -> 72^1000 which is 2.2 * 10^1857, there will necessarily be (assuming an average distribution of the inevitable duplicates) -> (2.2 * 10^1857) / (3.4 * 10^38) which is 6.3 * 10^1818 texts of 1000 characters corresponding to an md5 'code'; one could say that it is almost impossible to have a correspondence table. Therefore, if the string is very short (but already for 10 characters, you already need a table of 34 billion gigabytes), adding a 'salt' string is a satisfactory method and, on the other hand, using twisted characters in a password prevents a solution from being found in ridiculously small dictionaries. Hoping I haven’t made any mistakes in my calculations, I wish everyone good reflection.

fiddy · Answer

Yes, but you still agree with me that what man has created, he can also undo... Except when it comes to an exact science like mathematics ;-). The hash function is irreversible. Moreover, there is a loss of information. So, you can't retrieve the original message.  I agree with you, it must be hard...but there’s always a trick...right? Yes, there are tricks like brute force, dictionary attacks, or the use of rainbow tables. The principle is to hash the message. If the hash equals the sought hash, then we have a possible candidate for the solution. But if the message is complex, it won't be in a dictionary, and brute force will take too long. That’s why hash functions are still widely used.  This doesn't mean that MD5 is secure though. Given that it's possible to find collisions, certain security measures can be compromised. --  Google is your friend

lami20j · Answer

Hello,  No need to shout. And a greeting doesn't hurt.  Say the result for d6aa97d33d459ea3670056e737c99a3d -- 106485010510997108

Bobinours · Answer

I like Wikipedia too ;-) -- -= Bobinours =-

fiddy · Answer

I think it’s good if others don't say stupid things. Don't bother, there’s no systematic way to calculate the original message. MD5 should no longer be used because the generation of collisions has become very fast due to the efficiency of algorithms and can therefore be exploited to break systems that rely on MD5 ( http://fiddy.free.fr/... )  But there’s no attack on MD5 for the first pre-image. The most effective method is the use of rainbow tables. And that's precisely why you should always use a salt before hashing a password.  Try to find the message: 15007ce8d8be1b65c56421a6a498b7e4 And I’ll even give you a hint because I’m nice, the salt I added at the end is: #samushack  --  Google is your friend

arth · Answer

Well, you know when you cook, sometimes it's better with salt, well, it's the same here ... --  The wolf, solitary and mysterious.

fiddy · Answer

Decipher=not related to numbers. (+ harder to explain) With numbers, no. But we decipher what has been encrypted (unlike MD5 which is a hashing function and not encryption). And be careful not to confuse decrypt and decipher ;-))).  Otherwise, salting consists of concatenating a piece of data with the password (or other) to hash. The result is a hash that will not be in rainbow tables. http://en.wikipedia.org/wiki/Salt_(cryptography)  Best regards --  Google is your friend

le père · Answer

Hello  Sebsauvage, I feel like xortax couldn't decipher your response :D

sebsauvage · Answer

Yeah, well, apparently you didn't get it.

Xortax: The MD5 works as follows:

You give it a sequence of bytes of any length, and it outputs a 128-bit string.
Therefore, it can't be "decrypted", otherwise you could compress a DVD into 128 bits.

The only thing you can do to find out which string corresponds to an MD5 is to create all possible character strings, calculate their MD5 and compare with the MD5 you're looking for.

However, some enthusiasts have created gigantic databases of pre-calculated MD5s.

That's the link I provided: by chance, the MD5 you're searching for is present in that database, and the string corresponding to your MD5 is "????"

Okay?

Nabla's · Answer

It's nice of you to talk to us about rainbow tables, and even to have provided some websites, but you don't talk much about MD5 collisions, which allow for a string that returns the desired MD5 code...

sebsauvage · Answer

You don't talk much about MD5 collisions, which allow for a string that returns the desired MD5 code ...  Currently, nothing allows obtaining collisions for a specific MD5.  The only thing we can do is calculate strings that cause collisions, but you do not control the resulting MD5, and the source strings contain a block of several dozen bytes of random appearance.  It is therefore still not possible to forge a document or a string having a specific MD5, except through brute force.

fiddy · Answer

Indeed, the collision is quite different from the second pre-image attack: http://fiddy.free.fr/...  Best regards --  Google is your friend

chewie · Answer

It's normal that MD5 hasn't been cracked yet.

The algorithm is related to the machine's registers and their use in a specific order...

So, already, to be able to crack MD5, you need to be on the machine so that its signature can be identified... and even then, given that the generation doesn't necessarily go through the same registers, you won't get the same result if you enter the same password twice.

In short, if you want to know how it works, you just have to go to www.ietf.org (Internet Engineering Task Force).
You can look in the RFCs (memos describing the standards for how things related to the net have worked since 1969...).

There is an RFC that describes the logical functioning of MD5.

-------------------------------------------------------------------------------------------
There is an RFC for everything...

robert · Answer

Hello everyone  For searching the cleartext of an MD5 hash, I recommend http://hash.db.hk. It combines a database search with brute force using GPUs (Cuda).  The results are impressive.  Robert

davitz38 · Answer

But you can use online tools (they use large databases) like this one: http://www.stringfunction.com/md5-decrypter.html David

chatoune1 · Answer

Can someone help me decode this, please?  ac83c6cd2f06e9cf64a0756453489f26

anima-webms · Answer

It's possible at the university, the professor gave us an MD5 and we had to decrypt it, it took 6 hours of work, so it is possible.  MD5 to find: b747f94da7fbbc5def00394f21ce6822  Word found: Euclid  So it is entirely possible to find this kind of thing. But it is difficult to do so! I will not reveal the trick because it might be used for malicious purposes.

cornelius62 · Answer

Here’s a decent site to decrypt MD5  http://hash-decrypter.com

Decrypt md5 - Page 2

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