get string value of password from hash value

Question

I have created a hash value for password using the below code.. I am storing the value which is returned from the below method.

public static string CreateHash(string password)
{
    // Generate a random salt
    RNGCryptoServiceProvider csprng = new RNGCryptoServiceProvider();
    byte[] salt = new byte[24];
    csprng.GetBytes(salt);
    HashAlgorithm hashAlg = new SHA256CryptoServiceProvider();
    byte[] bytValue = System.Text.Encoding.UTF8.GetBytes(salt + ":" + password);
    // Hash the password and encode the parameters
    byte[] bytHash = hashAlg.ComputeHash(bytValue);
    return
        Convert.ToBase64String(bytHash);
}

Now i want to decode the value of the above created hash.. I need the string value of the password.. How do i do that..?

Also, it's almost always a bad idea to be able to retrieve the original value of the password. Whatever you're trying to achieve can be done in a better and more secure way. — Rob
– Rob ♦, Commented Jul 13, 2015 at 2:09
Are there any other algorithms which are 2 way so that i can implement it for my logic — axn7975
– axn7975, Commented Jul 13, 2015 at 2:15
Encryption and decryption, but as @Rob already said, it's not a good idea to store passwords in a way that is reversible. Passwords are stored nowadays as salted hashes so in case someone steals your password database, they will have a hard time reversing them. — MvdD
– MvdD, Commented Jul 13, 2015 at 2:24

Dan Lowe · Accepted Answer · 2015-07-13 02:06:57Z

4

SHA-256 is a one-way hash algorithm. You can't get the original text back from the hash, short of brute-force guessing.

answered Jul 13, 2015 at 2:06

Dan Lowe

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6 Comments

axn7975 Over a year ago

thanks..!! Are there any other algorithms which are 2 way so that i can implement it for my logic

Dan Lowe Over a year ago

It depends what you are trying to do. The usual use case for a hash is for password storage, in which case you would not want it to be reversible. Non-reversibility is the whole point.

axn7975 Over a year ago

I am looking for simple encrypt and decrypt functionality where passwords should be salted and stored in a cryptographic hash function

Dan Lowe Over a year ago

I think you're mixing up some terminology here. Hash functions are generally not reversible. Salt is really only useful for a hash function. If you want to encrypt and decrypt that's fine, but it would not use a salt. You would encrypt with a key, which you then use to decrypt later. But, this brings in another problem you need to deal with, storing and protecting those keys.

Scott Chamberlain Over a year ago

@DanLowe The IV of a encryption algorithm is the equivalent of a Salt in a hash.

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