I have a sha256 hash and i know that it consists on numbers and small characters and the length is 64 so is there any way to crack it?
SHA256 is a one-way hash, rather than an encryption. As such, you can't decrypt it. You can, however, bruteforce it.
MD5Decrypt has already covered more than 3 billion possible SHA256 strings, so there's a good chance you can find it here. Otherwise, you'll just need to try every possible combination there is, using what you already know.
Hope this helps! :)
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Is it possible to decrypt MD5 hashes?
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ร encodes into 0f93821e0fbc6d3736da7df2c73024aa
I was wondering if it's possible to decode the hash back into the unicode form. If so, how can I approach this or how can I perform this.
Any help is appreciated, thanks.
m5d is a hashing algorithm, that is by nature monodirectional.
You just can't "decode" it.
The only option you have is bruteforcing.
The whole point of a hash is to present a fixed-length output for arbitrary input with the property that the same input results in the same output. Cryptographic hash functions like MD5, or SHA-1 are even designed so they cannot be reversed easily. Thus, no, you cannot do that.
Also, just as a thought exercise that shows that in the general case it just cannot work: MD5 is 128 bits long, so how could you possibly recover input that's larger than that? There are an infinite number of strings turning into the same digest, so while you could find a string that has the same hash, you're not guaranteed to find the one you started with.
Whites11 has mentioned brute-forcing, however take into account this is not 'Decoding' the hash. This is simply hashing common inputs and comparing the 2 hashes to see if they match, unless you have a set of common inputs that may actually match the hash its very unlikely you will get anywhere with it.
Hashes are intentionally mono-directional, I can't think of why you would need to either you may need to rethink the logic of whatever project you're doing.
To summarize, you can't decode a hash, this is intentional and that's why hashing algorithms exist. And brute-forcing is hashing common inputs to see if they match your hash. It's commonly used for password cracking etc. Done with common password data sets. So may not be useful in your case.
http://www.md5online.org is a good example of bruteforcing, it is a database of previously bruteforce/tested hashes and their unicode inputs. You can try hashing a basic word like "password" and throwing it in there, it should show the original unicode input if it's a known hash!
Here are 2 excellent informative videos that cover hashing algorithms and brute-forcing hashes:
https://www.youtube.com/watch?v=b4b8ktEV4Bg
https://www.youtube.com/watch?v=7U-RbOKanYs
I am developing a large application and i need encryption when a data is traveling between two machines in different continents. I have never worked on encryption. I want a simple encryption which can be handled in PHP / Ruby / Python without any dependencies.
So i decided to use HMAC SHA1.
$pad=hash_hmac("sha1","The quick brown....","mykey");
This is what i found out after some research on the internet.
How hard it is to decrypt it if someone doesn't know the key? Also, any alternatives to this?
UPDATE - thanks for all the responses. Problem solved.
It's impossible to decrypt it, even if you know the key. HMAC SHA1 is a keyed hash algorithm, not encryption.
A hash is a cryptographic one-way function that always generates a value of the same length (I think SHA1 is 128-bits) regardless of the length of the input. The point of a hash is that, given the output value, it's computationally infeasible to find an input value to produce that output. A keyed hash is used to prevent rainbow table attacks. Even if you know the key you can't reverse the hash process.
For encryption you want to look at AES.
SHA1 is a one-way-hash function, by definition it is not decryptable by anyone. The question becomes if you have a plaintext T that hashes to H. How hard is it to find another T which also hashes to H.
According to Wikipedia, for SHA1, the best known brute force attack would take 2^51 evlautions to find a plain text that matches.
If you need actual encryption where you can reverse the process, you should take a look at AES256.
See:
http://en.wikipedia.org/wiki/Cryptographic_hash_function
For a general discussion on this.
Like Andrew said SHA1 is an hash algorithm and cannot be used for encryption (since you cannot get back the original value). The digest it produce can be used to validate the integrity of the data.
An HMAC is a construct above an hash algorithm that accept a key. However it's not for meant for encryption (again it can't be decrypted) but it allows you to sign the data, i.e. with the same key you'll be able to ensure the data was not tampered with during it's transfer.
Foe encryption you should look at using AES or, if applicable to your application, HTTPS (which will deal with more issues than you want to know about ;-)
SHA-1 , MD-5 are all one way Hashing algorithms.
They just generate a lengthy string. Each and every string when subjected to these functions will yield you a lengthy string which cannot be retained back.
They are far from encryptions.
If you are looking for encryption algorithms , go for AES (Advanced Encryption Standard) , DES (Data Encryption Standard) Algorithms.
As I say, this is a hash, so not an encryption/decryption problem. If you want to implement a straightforward encryption algorithm, I would recommend looking into XOR encryption. If the key is long enough (longer than the message) and your key sharing policy is suitably secure, this is a one time pad; otherwise, it can potentially be broken using statistical analysis.
I am reading about cryptography I was thinking about these properties of AES (that I use):
same message = same ouput
no message length secrecy
possible insecurity if you know the messages (does this actually apply to AES?)
I hear that AES is secure, but what if I want to theoritcaly improve these properties?
I was thinking I could do this:
apply encryption algorithm A
XOR with random data D (making sure the output looks random in case of any cipher)
generate random data that are longer than the original message
use hashing function F to allocate slots in random data (this scrambles the order bytes)
Inputs: Encryption algorith A, Data to XOR with D and a hashing function F
My questions are
does the proposed solution theoreticaly help with my concerns?
is this approach used somewhere?
Possible enhancements to this approach
I could also say that the next position chosen by hashing function will be altered using a checksum of the last decoded byte after the XOR step (that way the message has to be decoded from beginning to end)
If I was to use this to have conversation with someone, the data to XOR with could be the last message from the other person, but thats probably a vulnerability.
I am looking forward to your thoughts!
(This is only theoretical, I am not in need of more secure encryption, just trying to learn from you guys.)
Yeah.
Look. If you want to learn about cryptography, I suggest you read Applied Cryptography. Really, just do it. You will get some nice definitive learnings, and get an understanding of what is appropriate and what is not. It specifically talks about implementation, which is what you are after.
Some rules of thumb:
Don't make up your own scheme. This is almost universally true. There may be exceptions, but it's fair to say that you should only invent your own scheme if you've thoroughly reviewed all existing schemes and have specific quantifiable reasons for them not being good enough.
Model your attacker. Find out what scenarios you are intending to protect against, and structure your system so that it works to mitigate the potential attacks.
Complexity is your enemy. Don't make your system more complex then it needs to be.
Stay up to date. You can find a few mailing lists related to cryptography and (and hashing) join them. From there you will learn interesting implementation details, and be aware of the latest attacks.
As for specifically addressing your question, well, it's confusing. I don't understand your goal, nor do I understand steps 3 and 4. You might like to take a quick look here to gain an understanding of the different ways you can use a given encryption algorithm.
Hope this helps.
You assumptions are incorrect.
same message != same output
The output will not be the same if you encrypt the same message twice.
This is because you are suppsed to use different IVs'.
Message length can be hidden by adding random data to the plaintext.
Attacks have been demonstrated against AES with lesser number of rounds.
Full-round AES has not been compromised in any way.
Other than that I suggest you follow Noon Silks recommendation and read Applied Cryptography.
What's the point of the random data XOR? If it's truly random, how will you ever decrypt it? If you're saying the random data is part of the key, you might as well drop AES and use only the truly random key - as long as it's the same length (or longer than) the data and is never used more than once to encrypt. It's called a one-time pad, the only theoretically unbreakable encryption algorithm I know about.
If the random bits are pseudo-randomly generated, it's highly unlikely that your efforts will yield added security. Consider how many talented mathematicians were involved in designing AES...
EDIT: And I too highly recommend Applied Cryptography, it's an actually very readable and interesting book, not as dry as it may sound.
I realize this question might not be that programming related, and that it by many will sound like a silly question due to the intuitive logical fault of this idéa.
My question is: is it provable impossible to construct a cryptographic scheme (implementable with a turing-complete programming language) where the encrypted data can be decrypted, without exposing a decryption key to the decrypting party?
Of course, I can see the intuitive logical fault to such a scheme, but as so often with formal logic and math, a formal proof have to be constructed before assuming such a statement. Is such a proof present, or can it easely be constructed?
Thank you for advice on this one!
Edit: Thank you all for valuable input to this discussion!
YES!!! This already exists and are called zero knowledge protocols and zero knowledge proofs.
See http://en.wikipedia.org/wiki/Zero-knowledge_proof
However, you have to have a quite a good background in mathematics and crypto to understand the way it works and why it works.
One example of a zero knowledge protocol is Schnorr's ZK protocol
No; but I'm not sure you're asking what you want to be asking.
Obviously any person who is decrypting something (i.e. using a decryption key) must, obviously, have the key, otherwise they aren't decrypting it.
Are you asking about RSA, which has different keys for decrypting and encrypting? Or are you asking about a system where you may get a different (valid) result, based on the key you use?
If by "decrypted" you just mean arrive at the clear text in some way, then it is certainly possible to create such a cryptographic scheme. In fact it already exists:
Take an asymmetric encryption scheme, eg: RSA where you have the public key but not the private key. Now we get a message that's been encrypted with the public key (and therefore needs the private key to decrypt it). We can get the original message by "brute force" (yes, this'll take an enormously long time given a reasonable key/block size) going through all possible candidates and encrypting them ourselves until we get the same encrypted text. Once we get the same encrypted text we know what the decrypted text would be without ever having discovered the private key.
Yes.
Proof: Encryption can be considered as a black box, so you get an input and an output and you have no idea how the black box transforms the input to get the output.
To reverse engineer the black box, you "simply" need to enumerate all possible Turing machines until one of them does produce the same result as the one you seek.
The same applies when you want to reverse the encryption.
Granted, this will take much more time than the universe will probably live, but it's not impossible that the algorithm will find a match before time runs out.
In practice, the question is how to efficiently find the key that will decode the output. This is a much smaller problem (since you already know the algorithm).
It's called encoding.
But everyone with the encoding algorithm can "decrypt" the message. This is the only way of keyless encryption.
Imagine I have this:
$cdata = AES_256($data, $pass);
AES_256 implements the AES algorithm.
If I know the content of $cdata and the content of $data and also have
the AES_256() code, can I reverse engineer and find $pass?
Simple answer: NO.
This has been tested, and mentioned in the Wiki link.
A related-key attack can break up to 9
rounds of 256-bit AES. A
chosen-plaintext attack can break 8
rounds of 192- and 256-bit AES, and 7
rounds of 128-bit AES, although the
workload is impractical at 2128 -
2119.
Or put it another way: you have a better chance of being struck by lighting... on the same day you win the Lottery, than breaking it!
This is called a known-plaintext attack. A good cipher like AES should be immune to it, as the others explained.
If $pass is actually a password and not a 256-bit key, you may be in luck.
While it is far from trivial to perform, a brute-force attack against a normal password is much faster than brute-forcing a 256-bit key.
So modify one of the many password-brute-forcing tools, and you have a attack that (depending on the strength of the password) might take weeks to several years - but that is fast compared to 3x10^51 years...
Another quote, from Wikipedia:
AES permits the use of 256-bit keys.
Breaking a symmetric 256-bit key by
brute force requires 2^128 times more
computational power than a 128-bit
key. A device that could check a
billion billion (10^18) AES keys per
second would require about 3 x
10^51 years to exhaust the 256-bit
key space.
Brute forcing when you know the original text might be faster but still, 3 x 10^51 years is a long time. Plus there's the problem of probably not having a device that can check a billion billion (10^18) keys/second.
In short: everything is possible, but this is not feasible in the world we are now living in.
You could brute force it, but it would take a long time. As in decades or even longer. That's the point of encryption algorithms like AES.
AES, like all good crypto algorithms, doesn't rely on security through obscurity.
In other words, there are no "secrets" in the code, so you having the code won't help you particularly.
Known plaintext is a separate issue, which I don't know much about so I'll leave that up to the other answerers.
Of course not - the only approach is brute force.
Do you really think NIST is so stupid as to choose a cipher that is so easily cracked for a new standard?
with the power of super computers the time to crash AES encryption with be dramatically shortened.... I heard...
2x2^256 possible combinations is a lot to bruteforce. But bruteforcing is the only way. It would actually take about 3 decades. AES is the best Encryption possible right now I'd say. But that would only take that much time using a CPU. Because GPU's (Graphic Processing Units) are strictly math based, people have been making programs that only use the GPU to crack math based algorithms much more quickly than a CPU could. In other words AES might not last 3 decades. If only eternity codes were possible. Well looks like dynamic encryption may be the only way people can really hide their information in the near future.