Hash String

[shapper]

Hello,

How can I hash a string in C#?
I suppose I should use MD5 ... at least is what is used in ASP.NET
membership.

I need to has a string and compare it to an already hashed string.

Thanks,
Miguel

 

[Peter Morris]

string me = "Pete";
int hashCode = me.GetHashCode();

Am I missing something?

 

[Alberto Poblacion]

How can I hash a string in C#?
I suppose I should use MD5 ... at least is what is used in ASP.NET
membership.

I need to has a string and compare it to an already hashed string.

I use this two functions to get the MD5 hash of either a string or an array
of bytes:

public static byte[] GetHash(byte[] data)
{
MD5 md5 = MD5.Create();
byte[] result = md5.ComputeHash(data);
return result;
}
public static byte[] GetHash(string s)
{
byte[] myBytes = Encoding.UTF8.GetBytes(s);
return GetHash(myBytes);
}

 

[Peter Morris]

If you want a one-way hash for passwords try this...

public static string EncodePassword(string userName, string password)
{
TripleDESCryptoServiceProvider des;
MD5CryptoServiceProvider hashmd5;
byte[] pwdhash, buff;
hashmd5 = new MD5CryptoServiceProvider();
pwdhash = hashmd5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(userName));
des = new TripleDESCryptoServiceProvider();
des.Key = pwdhash;
des.Mode = CipherMode.ECB; //CBC, CFB
buff = ASCIIEncoding.ASCII.GetBytes(password);
string result =
Convert.ToBase64String(des.CreateEncryptor().TransformFinalBlock(buff, 0,
buff.Length));
return result;
}

 

[Ben Voigt [C++ MVP]]

string me = "Pete";
int hashCode = me.GetHashCode();

Am I missing something?

Yes. The result of GetHashCode is subject to change, even between
subsequent runs of the same program. Only while the program is still
running are you guaranteed consistent results. So it's useless for
comparing against a saved hash.

 

[shapper]

Yes.  The result of GetHashCode is subject to change, easicallyven between
subsequent runs of the same program.  Only while the program is still
running are you guaranteed consistent results.  So it's useless for
comparing against a saved hash.

Basically, in this case I am sending the user a confirmation email
after she/he registers on a web site.
On the email is the url. Something has follows:

www.mydomain.com/ConfirmPassword/?key=...

where key is an hash of a string created by joining the user UserName,
Accoount CreateDate, ...

So when the user goes to that URL I hash the same string again and
confirm the two to activate the account.

Isn't this possible?

Thanks,
Miguel

 

[Jon Skeet [C# MVP]]

Basically, in this case I am sending the user a confirmation email
after she/he registers on a web site.
On the email is the url. Something has follows:

www.mydomain.com/ConfirmPassword/?key=...

where key is an hash of a string created by joining the user UserName,
Accoount CreateDate, ...

So when the user goes to that URL I hash the same string again and
confirm the two to activate the account.

Isn't this possible?

Yup, and MD5 is probably the best bet for that.