How do I decrypt text in C#?

Question

I am using the function below to encrypt password and store it into my database. Now I need to decrypt it back and compare it with the login user. Please help me.

public static string encrypt_string_using_MD5(string s)
{
    byte[] byte_array = System.Text.Encoding.Default.GetBytes(s);

    System.Security.Cryptography.HashAlgorithm alg =
        System.Security.Cryptography.HashAlgorithm.Create("MD5");

    byte[] byte_array2 = alg.ComputeHash(byte_array);

    System.Text.StringBuilder sb
        = new System.Text.StringBuilder(byte_array2.Length);

    foreach(byte b in byte_array2)
    {
        sb.AppendFormat("{0:X2}", b);
    }

    return sb.ToString();
}

You didn't encrypt it - you hashed it. See: [http://stackoverflow.com/questions/4948322/fundamental-difference-between-hashing-and-encryption-algorithms](http://stackoverflow.com/questions/4948322/fundamental-difference-between-hashing-and-encryption-algorithms) — Sebastian Schumann, Sep 16 '15 at 07:03

score 5 · Answer 1 · answered Sep 16 '15 at 07:03

You cannot Decrypt Hash. Hash is like signature of your original content. What you can do is to store this Hash in database. Whenever user enters password. you compute the hash of value user entered and compare it with stored hash and if it matches then authentication is succesfull

score 0 · Answer 2 · answered Sep 16 '15 at 07:02

You can not decrypt it, because it is not encrypted.

You create a hash of the text, and not an encrypted version.

A hash is like a fingerprint of data. This can be used for example to safely store passwords in a database. When someone wants to login again, you again calculate the hash and check the new hash against the one the in database to see if they match. If they do, then the password is the same and the user can login.

A good explanation can be found at http://www.securityinnovationeurope.com/blog/whats-the-difference-between-hashing-and-encrypting

score 0 · Answer 3 · answered Sep 16 '15 at 07:59

0

Hence you use MD5, it's irreversible. Why are you sending passwords as plain text anyway...?

Either way, when comparing values (one plain, one hashed) hash the plain one and compare that.

answered Sep 16 '15 at 07:59

EddieDemon

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How do I decrypt text in C#?

3 Answers3