Hi,

I have many questions.

1. I need to create a Hash value of a String. Does anybody has a
function? I am havin troubles doing my own function, because i fail
converting a Byte() to a String.

2. What is the most security algorithm? MD5, SHA1, SHA512??

3. What is the difference bettewn Dim x as byte() and Dim x() as Byte

4. I debug my own function, i am getting surprise when i enter a long
string like 500 characters, and ComputeHash return me a string of 35
characters!! I think i am doing something wrong here.

Thanks

Alfredo Barrientos

        private void button1_Click(object sender, EventArgs e)
        {
            string s = "My string to hash.";
            byte[] ba = Encoding.UTF8.GetBytes(s);

            byte[] md5Hash = MD5.Create().ComputeHash(ba);
            string base64Hash = Convert.ToBase64String(md5Hash);
            Console.WriteLine("MD5 hash of string is:" + base64Hash);
            Console.WriteLine("MD5 hash length in bytes:" + md5Hash.Length);

            byte[] sha1Hash = SHA1.Create().ComputeHash(ba);
            base64Hash = Convert.ToBase64String(sha1Hash);
            Console.WriteLine("SHA1 hash of string is:" + base64Hash);
            Console.WriteLine("SHA1 hash length in bytes:"+
sha1Hash.Length);

            byte[] sha256Hash = SHA256.Create().ComputeHash(ba);
            base64Hash = Convert.ToBase64String(sha256Hash);
            Console.WriteLine("SHA256 hash of string is:" + base64Hash);
            Console.WriteLine("SHA256 hash length in bytes:" +
sha256Hash.Length);
        }

// Output:
MD5 hash of string is:DS4DrhUB33YBfoK8S7PJ6g==
MD5 hash length in bytes:16
SHA1 hash of string is:TNH/hNKWZKVDK5/RbTgD+9c4lQg=
SHA1 hash length in bytes:20
SHA256 hash of string is:M3GLzAsXhdtIF+pcZ/fWDD5rcfbDptb3RzkFdmM/0jE=
SHA256 hash length in bytes:32


The strength of the hash follows the order you listed.

As you see above, the hash is always the same size depending on the hash
algo you pick.  md5 is 16 bytes, sha1 is 20, sha256 is 32, etc.

Thank you very much William,

But, I dont understand how is possible to get a diferent hash value for
numbers from 1 to 1 000 000 000 000 000 000 000 000 000 000 000 000, if
my maximun combination is 1 00 000 000 000 000 000 000 000 000 000 000
- 1?

Thanks,

Alfredo Barrientos

The hash space is finite.  The data space that you might hash is infinite.
It follows there is an infinite number of hash collisions.

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Hello Alfredo,

hash algorithms (especially the more sophisticated ones) are complex beasts.
Grab a copy of Schneier "Applied Cryptography" if you want the details.

---------------------------------------
Dominick Baier - DevelopMentor
http://www.leastprivilege.com

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Thank you very much.

How many algorithms does .net support?

Thanks,

Alfredo Barrientos

Hello Alfredo,

http://www.leastprivilege.com/SupportedHashingAlgorithmsForPasswordDeriveBytes.aspx

---------------------------------------
Dominick Baier - DevelopMentor
http://www.leastprivilege.com

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