Implementing MD5 Encryption in C # (reprint)

Method One

First, let's briefly introduce MD5

MD5 's full name is Message-digest algorithm 5 (Information-Digest algorithm, in the early 90 by MIT Laboratory for Computer Science and RSA Data Security Inc Ronald L. Rive St developed, developed by MD2, Md3 and MD4.

MD5 has a very good security (because it has irreversible characteristics, encrypted ciphertext after decryption and the same as before the encryption of the same probability)

Reference using System.Security.Cryptography; Using System.Text;

The specific code is as follows (written in the button's Click event): byte[] result = Encoding.Default.GetBytes (This.tbPass.Text.Trim ()); Tbpass is the text box for entering the password MD5 MD5 = new MD5CryptoServiceProvider (); byte[] Output = Md5.computehash (result); This.tbMd5pass.Text = bitconverter.tostring (Output).  Replace ("-", "" "); Tbmd5pass text box for output encrypted text

Method Two

C # MD5 encryption (top) string A; Data before encryption string B; Data b=system.web.security.formsauthentication.hashpasswordforstoringinconfigfile after encryption (A, "MD5")

Using System; Using System.Security.Cryptography;

Method 2

public static string GetMD5 (String myString)

{

MD5 MD5 = new MD5CryptoServiceProvider (); byte[] Fromdata = System.Text.Encoding.Unicode.GetBytes (myString); byte[] Targetdata = Md5.computehash (Fromdata); string byte2string = null;

for (int i=0;   i<targetdata.length; i++) {byte2string + = Targetdata[i]. ToString ("X");

}

return byte2string;

}

Using System.Security.Cryptography;

<summary>

MD5 encryption for a string

</summary>

<param name= "StrText" > Strings to be encrypted </param>

<returns> string after encryption </returns> public static string Md5encrypt (String strText) {

MD5 MD5 = new MD5CryptoServiceProvider (); Byte[] result = Md5.computehash (System.Text.Encoding.Default.GetBytes (StrText)); return System.Text.Encoding.Default.GetString (Result);

}

C # MD5 encryption using System.Security.Cryptography;

private void Btnok_click (object sender, System.EventArgs e)

{

String strconn = "Server=192.168.0.51;database=chengheng; User Id=sa; Pwd=123 ";

if (texName.Text.Trim () = = "")

{

This. RegisterStartupScript ("SF", "<script language= ' JavaScript ' >alert (' User name cannot be empty ');d ocument.all (' Texname '). Focus (     ) </script> "); Return

}

else if (texPassword.Text.Trim () = = "")

{

This. RegisterStartupScript ("SFS", "<script language= ' JavaScript ' >alert (' password cannot be null ');

document.all (' Texpassword '). Focus () </script> ");

Return

} else

{

The obtained password encryption is compared to the secret password in the database byte[] by = Md5.computehash (UTF. GetBytes (TexPassword.Text.Trim ()));

String resultpass = System.Text.UTF8Encoding.Unicode.GetString (by); Conn. Connectionstring=strconn;

SqlCommand comm = new SqlCommand ();

String name = TexName.Text.Trim (). ToString ();

comm.commandtext= "Select ruser_pwd,ruser_nm from ruser where accountno = @name";

Comm. Parameters.Add ("@name", sqldbtype.nvarchar,40);

Comm. parameters["@name"]. Value=name;

try{

Conn. Open ();

Comm. Connection=conn;

SqlDataReader Dr=comm. ExecuteReader ();

if (Dr. Read ())

{

The user exists, checks the password

if (Dr. GetValue (0). Equals (Resultpass))

{

String User_name=dr. GetValue (1). ToString ();

String User_accountno=texname.text.trim ();

session["Logon_name"]=user_name;

session["Logon_accountno"]=USER_ACCOUNTNO;

Login successful, page oriented

}else

{

This. RegisterStartupScript ("WP", "<script language= ' JavaScript ' >alert (' Password error, please check. ') </script> ");

}

}

Else

{

This. RegisterStartupScript ("Nu", "<script language=javascript>alert (' username not present, please check. ') </script> ");

}

}

catch (Exception exec)

{

This. RegisterStartupScript ("WC", "<script language=javascript>alert (' Network connection is different, please try again later.") ') </script> ");

}

Finally

{

Conn. Close ();

}

}

}

Method three C # MD5 encryption

C # Development Note One, C # md5-16 bit encryption instance, 32-bit encryption instance (two methods)

Environment: Vs.net2005/sql SERVER2000/XP Test through 1.MD5 16-bit encryption instance using System; Using System.Collections.Generic; Using System.Text; Using System.Security.Cryptography;

namespace MD5

{

Class Program

{

static void Main (string[] args)

{

Console.WriteLine (UserMd5 ("8"));

Console.WriteLine (Getmd5str ("8"));

}

/**////<summary>

MD5 16-bit encryption password is uppercase

</summary>

<param name= "Convertstring" ></param>

<returns></returns>

public static string Getmd5str (String convertstring)

{

MD5CryptoServiceProvider MD5 = new MD5CryptoServiceProvider ();

String t2 = bitconverter.tostring (Md5.computehash (UTF8Encoding.Default.GetBytes (convertstring)), 4, 8);

t2 = T2. Replace ("-", "" ");

return T2;

}

/**////<summary>

MD5 16-bit encryption password is lowercase

</summary>

<param name= "Convertstring" ></param>

<returns></returns>

public static string Getmd5str (String convertstring)

{

MD5CryptoServiceProvider MD5 = new MD5CryptoServiceProvider ();

String t2 = bitconverter.tostring (Md5.computehash (UTF8Encoding.Default.GetBytes (convertstring)), 4, 8);

t2 = T2. Replace ("-", "" ");

t2 = T2. ToLower ();

return T2;

}

/**////<summary>

MD5 32-bit encryption

</summary>

<param name= "str" ></param>

<returns></returns>

static string UserMd5 (String str)

{

string cl = str;

string pwd = "";

MD5 MD5 = MD5. Create ();

Instantiate a MD5 pair of images

After the encryption is an array of byte type, here should pay attention to the choice of coding utf8/unicode, etc.

Byte[] s = Md5.computehash (Encoding.UTF8.GetBytes (CL));

Converts an array of byte types to a string by using a loop, which is a regular character formatting the resulting

for (int i = 0; i < s.length; i++)

{

The resulting string is formatted using the hexadecimal type. The formatted character is a lowercase letter, and if uppercase (X) is used, the character after the format is uppercase characters

PWD = pwd + s[i]. ToString ("X");

}

return pwd;

}

}

}

Using System.Security.Cryptography; Using System.Text;

public static string Stringtomd5hash (String inputstring)

{

MD5CryptoServiceProvider MD5 = new MD5CryptoServiceProvider ();

byte[] encryptedbytes = Md5.computehash (Encoding.ASCII.GetBytes (inputstring)); StringBuilder sb = new StringBuilder ();

for (int i = 0; i < encryptedbytes.length; i++)

{

Sb. AppendFormat ("{0:x2}", Encryptedbytes[i]);

}

Return SB. ToString ();

}

Second, first introduced in the interface: using System.Web.Security;

Assuming the password dialog name password, encrypt the input password into the variable pwd, the following statement:

string pwd = formsauthentication.hashpasswordforstoringinconfigfile (password. Text, "MD5");

If you want to enter the PWD, so that the actual database password is 202***** and so garbled.

If you want to log in to the query:

Select Username,password from users where username= ' "+ Username.text +" ' and password= ' "+ pwd +" '

Because MD5 cannot decrypt, only the original password is encrypted and compared with the encrypted password in the database.

Third, C # MD5 encryption method 16-bit or 32-bit

public string MD5 (string Str,int code)

{

if (code==16)//16-bit MD5 encryption (takes 32-bit encrypted 9~25 characters)

{

return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile (str, "MD5"). ToLower (). Substring (8,16);

} ELSE//32 bit encryption

{

return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile (str, "MD5"). ToLower ();

}

}

Four, to do a website, is bound to involve the user login, user login must involve password, password must involve security, security must involve encryption. Encryption now the most popular is also said that the most secure algorithm is the MD5 algorithm, MD5 is an irreversible algorithm, that is, after the plaintext is encrypted, according to encrypted ciphertext can not restore the plaintext. There are a lot of web sites dedicated to MD5, Baidu search MD5 on a lot of search, this morning bored to try a few broken secret website, 6 bits of pure digital password MD5 ciphertext can restore the plaintext, long point or with characters on the die. They are used in comparison, that is, the inclusion of plaintext and ciphertext into the database, through the comparison of ciphertext to determine the clear text, after all, the limited data collected, so the password is very limited. Pull away, break the secret MD5 need a lot of money, because to an ultra-fast computing and a search performance of the database and super-large database ingest. But encryption is easier. Here is a MD5 encryption method I wrote in C #, using the. NET, through the Md5_app. StringToMD5 (string str, int i) can be called directly:

public class Md5_app

{

Public Md5_app ()

{

}

public static string StringToMD5 (string str, int i)

{

Get the field to encrypt and convert to byte[] Array

byte[] data = System.Text.Encoding.Unicode.GetBytes (str. ToCharArray ());

Establishing Cryptographic Services

System.Security.Cryptography.MD5 MD5 = new System.Security.Cryptography.MD5CryptoServiceProvider ();

Encrypt byte[] Array

Byte[] result = Md5.computehash (data);

Convert an encrypted array into a field

if (i = = && str! = string. Empty)

{

return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile (str, "MD5"). ToLower (). Substring (8, 16);

}

else if (i = = && str! = string. Empty)

{

return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile (str, "MD5"). ToLower ();

}

Else

{

Switch (i)

{

Case 16:return "000000000000000";

Case 32:return "000000000000000000000000000000";

Default:return "Make sure the second parameter is 16 or 32 when calling the function";

}

}

}

This article from Csdn Blog, reproduced please indicate the source: http://blog.csdn.net/shenghui188/archive/2010/03/28/5423959.aspx

Implementing MD5 Encryption in C # (reprint)