I have code to generate SHA512 from string.
public static string GetCrypt(string text)
{
string hash = "";
SHA512 alg = SHA512.Create();
byte[] result = alg.ComputeHash(Encoding.UTF8.GetBytes(text));
hash = Encoding.UTF8.GetString(result);
return hash;
}
Now I must convert hash back to string. Any ideas how can it be done? Thank you.
Hashes are 1-way. You can't get it back (easily). you might want actual encryption.
Yes. Hashes are one-way. Please use symmetric encryption classes like RijndaelManaged.
Here is a RijndaelSimple class that I am using:
http://www.obviex.com/samples/encryption.asp
The cached version of the same link is here:
http://webcache.googleusercontent.com/search?q=cache:WyVau-XgIzkJ:www.obviex.com/samples/encryption.asp&hl=en&prmd=imvns&strip=1
You cant convert a hash back to string from which you computed the hash.
If you want it then you would have to compare the hash with each of the target strings hash.
If one of them matches with the hash,then that hash comes from the target string.
Its use: If you want to store passwords in database,you can store its hashes instead of passwords.So even if a hacker gets access to your database,he cant get the password cuz it is hashed.The only way to know the string through which we created the hash is to match it with the desired string!
Related
For a project I need to generate a SHA256 encrypted string in C#.
The requirements are Key: todaysDate and Value: "exampleString".
How can i realize that in C#? As far as I see the SHA256-Class does not contain a property for key in C#.
SHA256 isn't an encryption algorithm, it's a hash algorithm. In other words, it's a one way function whose job is to take an input of any length and produce an output of fixed length with low collisions that's always the same for the same input. Thus, it doesn't receive a key as an input because the nature of hashing is quite different from that of encryption.
If you want to encrypt something with a key and later decrypt it by having the same key, look into symmetric encryption like AES (e.g. using the AesManaged class).
You should do your own homework. If we do it for you, you learn nothing.
Also, as Theodoros mentioned, SHA256 is a hash, not encryption. A hash is a cryptographic checksum that is used to validate or compare data. It can not be reversed into the original plaintext, which is a requirement of encryption.
How can i realize that in C#? As far as I see the SHA256-Class does not contain a property for key in C#.
Either you or the person who gave you the assignment doesn't understand what is being asked.
SHA256 doesn't have a key or a value, it only has data going in and a hash coming out. No matter how much data you run through it, the size of the hash does not change, although it's value does. You can think of a hash as a fingerprint for a particular dataset.
Maybe something like this:
public static string sha256_hash(string sValue) {
StringBuilder oResHash = new StringBuilder();
using (SHA256 oHash = SHA256Managed.Create()) {
Encoding oEnc = Encoding.UTF8;
byte[] baResult = oHash.ComputeHash(oEnc.GetBytes(sValue));
foreach (byte b in baResult)
oResHash.Append(b.ToString("x2"));
}
return oResHash.ToString();
}
I am writing a part of code to change string into hash
String hash = GetHashString("A"); //return 7FC56270E7A70FA81A5935B72EACBE29
My question is how can I get back "A" when I pass in the hash code ?
7FC56270E7A70FA81A5935B72EACBE29
Hashes are not meant to be reversible. If you want to compare its origin with another string, just hash the second one too and then compare their hashes.
I have an Excel workbook currently acting as a booking diary. It has users/passwords stored in a database, the passwords are hashed using SHA1 (with no salt at the moment to make this easier)
When I store a user with password password I get the following hash in the database:
5baa61e4c9b93f3f0682250b6cf8331b7ee68fd8
This is backed up by trying the string here and here, both give the same result as my VBA SHA1 function
So now I want to move this application into C# (probably and ASP.NET web app eventually), so I'm using the following to generate the SHA1 hash:
// Convert plain text into a byte array
byte[] plainTextBytes = Encoding.Default.GetBytes("password");
// Define hash object
HashAlgorithm hash = new SHA1Managed();
// Compute hash value of our plain text
byte[] hashBytes = hash.ComputeHash(plainTextBytes);
// Convert result into a base64-encoded string
string hashValue = Convert.ToBase64String(hashBytes);
Console.WriteLine(hashValue);
but this outputs
W6ph5Mm5Pz8GgiULbPgzG37mj9g=
I must have done some small thing wrong, but I can't work out what it is :(. I have tried the different encoding types (UTF8, ASCII, Unicode) but none produce the correct hash
Can someone shed some light on this for me please?
You converted the string to base64, although it seems you want hex. Convert to hex instead.
You should convert hashBytes into HexString, not Base64.
string hashValue = Convert.ToBase64String(hashBytes);
That's the problem statement, the result string you quoted was not base64 encoded, it was encoded in hex. You get the value you are looking for with:
string hashValue = BitConverter.ToString(hashBytes).Replace("-", "").ToLower();
Which produces:
"5baa61e4c9b93f3f0682250b6cf8331b7ee68fd8"
How to convert Md5Hash values to string..
i have convert string values to hash..
i have used the to method to convert MD5Hash to string
`
public static string ConvertStringtoMD5(string strword)
{
MD5 md5 = MD5.Create();
byte[] inputBytes = System.Text.Encoding.ASCII.GetBytes(strword);
byte[] hash = md5.ComputeHash(inputBytes);
StringBuilder sb = new StringBuilder();
for (int i = 0; i < hash.Length; i++)
{
sb.Append(hash[i].ToString("x2"));
}
return sb.ToString();
}
`
string has=ConvertStringtoMD5("prasad");
its returns hash value = 'c246ad314ab52745b71bb00f4608c82a'
using this hash values i need to get the string called prasad
how can i achive this, can you suggest to achive this..
Hashes are one-way. They are not designed to be unencoded once they are encoded. That being said, they can be cracked using Rainbow Tables. To create your own rainbow table in C#, you can look at this article.
Keep in mind that Rainbow Tables do have limitations and do not work 100% of the time. This is especially true if the MD5 hash has been salted.
Hashing functions are only one way functions - there is no way to get the input.
You could try using e.g. rainbow tables, but because number of possible hashes is limited, there is a chance that you will get another string with the same MD5 hash instead of the input.
Hashing is one way function. This means that you can't get the original input by using the hashed output.
One of the ways to compare if two inputs are the same is to hash the new input and check it against the already hashed output you already have, then simply check if the values are the same. Keep in mind, that in some algorithms, collisions can occur, which means two different inputs might generate the same output.
MD5 is a one-way hash, you cannot (without brute force techniques) obtain the original string from the hash.
You can't reverse MD5 method, it's a hashing algorithm. There are infinite values that can result in the same hash string.
Can someone reverse this handy hash code I'm using?
using System.Security.Cryptography;
public static string EncodePasswordToBase64(string password)
{ byte[] bytes = Encoding.Unicode.GetBytes(password);
byte[] inArray = HashAlgorithm.Create("SHA1").ComputeHash(bytes);
return Convert.ToBase64String(inArray);
}
Everything I end up doing fails horribly :(.
No, you can't reverse a hash. The typical process is to compare other input to the hash you have, to check if they are the same.
Like (pseudo):
initial = Hash(password);
possible = Hash("test");
if( initial == possible ){
// we infer that password = "test"
}
But note that SHA1, SHA0, and MD5 should no longer be used; (due to various degrees of breaking in each). You should use SHA-2
The only real way of "unhashing" is using a rainbow table, which is a big table of hashes computed for all possible inputs. You look up the hash and get what was probably the original input.
http://en.wikipedia.org/wiki/Rainbow_table
You cannot un-hash SHA1, MD5, or any other one-way hash method unfortunately. Though it is possible to undo BASE-64.
SHA is an NSA acronym for "Secure Hash Algorithm".
Secure Hashes are hard to reverse by definition -- otherwise they would not be Secure.
You need to use a reversible hash function if you want to be able to easily compute sources that will generate the same hash (and even then you might not get the original source due to hash collisions where more than one source input can result in the same hash output).