MD5 encryption and md5 decryption

MD5 encryption and md5 decryption
Zookeeper

First, let's briefly introduce MD5.

The full name of MD5 is message-digest algorithm 5 (Information-digest algorithm, which was developed by mit laboratory for computer science and rsa data security inc ronald l in early 1990s. developed by rivest and developed by md2, md3, and md4.

MD5 has good security (because it has irreversible characteristics, it is very unlikely that encrypted ciphertext will be the same as that before encryption)

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

The Code is as follows (written in the Click Event of the button ):
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 is the Text box for outputting encrypted Text

Method 2

C # md5 encryption (on)
String a; // pre-encryption data
String B; // encrypted data
B = System. Web. Security. FormsAuthentication. HashPasswordForStoringInConfigFile (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>
/// Perform MD5 encryption on a string
/// </Summary>
/// <Param name = "strText"> string to be encrypted </param>
/// <Returns> encrypted string </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; password = 123 ";
If (texName. Text. Trim () = "")
{
This. registerStartupScript ("sf", "<script language = 'javascript '> alert ('user name cannot be blank'); document. all ('textname '). focus () </script> ");
Return;
}
Else if (texPassword. Text. Trim () = "")
{
This. registerStartupScript ("sfs", "<script language = 'javascript '> alert ('password cannot be blank'); document. all ('textpassword '). focus () </script> ");
Return;
}
Else
{
// Encrypt the obtained password and the password added to the database
Byte [] by = md5.ComputeHash (utf. GetBytes (texPassword. Text. Trim ()));
String resultPass = System. Text. UTF8Encoding. Unicode. GetString ();
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 ())
{
// Check the password if the user exists
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;
// Log on to the Apsara stack console.

}
Else
{
This. RegisterStartupScript ("wp", "<script language = 'javascript '> alert ('incorrect password, please check. ') </Script> ");
}
}
Else
{
This. RegisterStartupScript ("nu", "<script language = javascript> alert ('user name does not exist, 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 3
C # MD5 Encryption

C # Development Notes 1, C # MD5-16 bit encryption instance, 32 bit encryption instance (two methods)

Environment: vs. net2005/sqlserver2000/xp passed the test
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>
/// The MD5 16-bit encrypted password is capitalized
/// </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>
/// The MD5 16-bit encrypted password is in lower case
/// </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 an md5 object
// After encryption, it is an array of the byte type. Pay attention to the selection of UTF-8/Unicode encoding.
Byte [] s = md5.ComputeHash (Encoding. UTF8.GetBytes (cl ));
// Convert an array of the byte type into a string by using a loop. This string is obtained by regular character formatting.
For (int I = 0; I <s. Length; I ++)
{
// Use the hexadecimal format of the obtained string. The characters in the format are lowercase letters. If uppercase letters (X) are used, the characters in the format are uppercase letters.

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 ();
}

2. first introduce using System. Web. Security in the interface;

Assume that the password dialog box is named password. The entered password is encrypted and saved to the variable pwd. The statement is as follows:

String pwd = FormsAuthentication. HashPasswordForStoringInConfigFile (password. Text, "MD5 ");

Enter pwd if you want to enter it, so the actual password of the database is garbled like 202.

For Login query, you must:

Select username, password from users where username = '"+ UserName. Text +"' and password = '"+ pwd + "'

Because MD5 cannot be decrypted, you can only encrypt the original password and compare it with the encrypted password in the database.

III. C # MD5 Encryption Method 16-bit or 32-bit

Public string md5 (string str, int code)
{
If (code = 16) // 16-bit MD5 encryption (take 32-bit encryption 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 ();
}
}

4. When creating a website, user logon is required, and user logon must involve passwords. Passwords must be secure and security must be encrypted.
Encryption is currently the most popular and it is said that the most secure algorithm is the MD5 algorithm. MD5 is an irreversible algorithm, that is, after the plaintext is encrypted, the plaintext cannot be restored Based on the encrypted ciphertext.
At present, there are a lot of websites dedicated to MD5 password cracking. Baidu searched for MD5 and found a lot. This morning I tried several websites boring, the MD5 ciphertext of a 6-digit password can be restored to the plaintext, and long characters or characters may not work. They use a poor comparison, that is to say, they put the included plaintext and ciphertext into the database and determine the plaintext through the comparison of the ciphertext. After all, the included data is limited, so the password to be cracked is very limited.
It takes a lot of MONEY to break down the password MD5, because it requires a computer with ultra-fast computation, a database with super-high search performance, and a super-large database. However, encryption is relatively simple. The following is an MD5 encryption method written in C #. NET. It can be directly called through MD5_APP.StringToMD5 (string str, int I:

Public class MD5_APP
{
Public MD5_APP ()
{
}

Public static string StringToMD5 (string str, int I)
{
// Obtain the field to be encrypted and convert it to a Byte [] Array
Byte [] data = System. Text. Encoding. Unicode. GetBytes (str. ToCharArray ());
// Create an encryption service
System. Security. Cryptography. MD5 md5 = new System. Security. Cryptography. MD5CryptoServiceProvider ();
// Encrypt Byte [] Arrays
Byte [] result = md5.ComputeHash (data );
// Convert the encrypted array into a field
If (I = 16 & str! = String. Empty)
{
Return System. Web. Security. FormsAuthentication. HashPasswordForStoringInConfigFile (str, "MD5"). ToLower (). Substring (8, 16 );
}
Else if (I = 32 & 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 ";
}

}
}

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