How the MD5 encryption and decryption in C#

Question

Hi friend How to implement the MD5 encryption and decryption in C#? Thanks.

Vulpes · Answer

OK here's an example of using AES to encrypt and decrypt a password: using System; using System.Text; using System.IO; using System.Security.Cryptography; class Program { static void Main() { // generate a random key and initialization vector 16 bytes long Random rand = new Random(); byte[] key = new byte[16]; byte[] iv = new byte[16]; for(int i = 0; i for(int i = 0; i string password = Geronimo29; byte[] data = Encoding.ASCII.GetBytes(password); byte[] encrypted = Encrypt(data key iv); byte[] decrypted = Decrypt(encrypted key iv); string password2 = Encoding.ASCII.GetString(decrypted); Console.WriteLine(Decrypted password is  + password2); // Geronimo29 Console.ReadKey(); } static byte[] Encrypt(byte[] data byte[] key byte[] iv) { using (Aes algo = Aes.Create()) { using (ICryptoTransform encryptor = algo.CreateEncryptor(key iv)) { return Crypt(data encryptor); } } } static byte[] Decrypt(byte[] data byte[] key byte[] iv) { using (Aes algo = Aes.Create()) { using (ICryptoTransform decryptor = algo.CreateDecryptor(key iv)) { return Crypt(data decryptor); } } } static byte[] Crypt(byte[] data ICryptoTransform cryptor) { var ms = new MemoryStream(); using(Stream cs = new CryptoStream(ms cryptor CryptoStreamMode.Write)) { cs.Write(data 0 data.Length); } return ms.ToArray(); } }

Ananth G · Answer

Encryption Sometimes we want to encrypt the values that time we use MD5 Encryption and Decryption Here i give the code for Encryption and Decryption. passPhrase saltValue initVector this variables are the key for Encryption and Decryption public static string passPhrase = YOUR KEY1; public static string saltValue = YOUR KE2; public static string initVector = YOUR KE3; public static string FunForEncrypt(string objText) { int keySize = 256; int passwordIterations = 03; string hashAlgorithm = MD5; byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector); byte[] saltValueBytes = Encoding.ASCII.GetBytes(saltValue); byte[] plainTextBytes = Encoding.UTF8.GetBytes(objText); PasswordDeriveBytes password = new PasswordDeriveBytes ( passPhrase saltValueBytes hashAlgorithm passwordIterations ); byte[] keyBytes = password.GetBytes(keySize / 8); RijndaelManaged symmetricKey = new RijndaelManaged(); symmetricKey.Mode = CipherMode.CBC; ICryptoTransform encryptor = symmetricKey.CreateEncryptor ( keyBytes initVectorBytes ); MemoryStream memoryStream = new MemoryStream(); CryptoStream cryptoStream = new CryptoStream ( memoryStream encryptor CryptoStreamMode.Write ); cryptoStream.Write(plainTextBytes 0 plainTextBytes.Length); cryptoStream.FlushFinalBlock(); byte[] cipherTextBytes = memoryStream.ToArray(); memoryStream.Close(); cryptoStream.Close(); string cipherText = Convert.ToBase64String(cipherTextBytes); cipherText = HttpUtility.UrlEncode(cipherText); return cipherText; } Decryption : this below code used to Decrypt the text public static string FunForDecrypt(string cipherText) { string plainText = ; int keySize = 256; int passwordIterations = 03; string hashAlgorithm = MD5; try { cipherText = HttpUtility.UrlDecode(cipherText); byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector); byte[] saltValueBytes = Encoding.ASCII.GetBytes(saltValue); byte[] cipherTextBytes = Convert.FromBase64String(cipherText); PasswordDeriveBytes password = new PasswordDeriveBytes ( passPhrase saltValueBytes hashAlgorithm passwordIterations ); byte[] keyBytes = password.GetBytes(keySize / 8); RijndaelManaged symmetricKey = new RijndaelManaged(); symmetricKey.Mode = CipherMode.CBC; ICryptoTransform decryptor = symmetricKey.CreateDecryptor ( keyBytes initVectorBytes ); MemoryStream memoryStream = new MemoryStream(cipherTextBytes); CryptoStream cryptoStream = new CryptoStream ( memoryStream decryptor CryptoStreamMode.Read ); byte[] plainTextBytes = new byte[cipherTextBytes.Length]; int decryptedByteCount = cryptoStream.Read ( plainTextBytes 0 plainTextBytes.Length ); memoryStream.Close(); cryptoStream.Close(); plainText = Encoding.UTF8.GetString(plainTextBytes 0 decryptedByteCount); } catch (Exception ex) { plainText = ; } return plainText; }

Ken H · Answer

Vulpes Can you give us a c #-based demo examples? Thanks!

Vulpes · Answer

To allow for both encryption and decryption using the same key (i.e. symmetric encryption) I'd use AES which is very secure. However what's usually done in practice with shopping sites when a user forgets his/her password is to issue a temporary password to allow him/her to sign in and then change the password to something permanent.

Ken H · Answer

Vulpes For safety's sake what method should we adopt to achieve this? What I mean is: saved to the database in encrypted form when the user forgets the password it needs to be converted to plaintext passwords. Thank.

Vulpes · Answer

Note that MD5 is a hashing algorithm and as such only supports one way encryption i.e. you can't decrypt it. It is however useful for comparing files to see whether they're the same for detecting errors when transmitting data or for hashing passwords.

Ramesh Maruthi · Answer

using System ; using System . Collections . Generic ; using System . Linq ; using System . Text ; using System . Security . Cryptography ; using System . IO ; namespace lockTest { class Program { static void Main ( string [] args ) { string hash = GetHash ( lockTest.pdb ); Console . WriteLine ( Hash: {0}  hash ); Console . ReadKey (); } public static string GetHash ( string pathSrc ) { string pathDest = copy_ + pathSrc ; File . Copy ( pathSrc  pathDest  true ); String md5Result ; StringBuilder sb = new StringBuilder (); MD5 md5Hasher = MD5 . Create (); using ( FileStream fs = File . OpenRead ( pathDest )) { foreach ( Byte b in md5Hasher . ComputeHash ( fs )) sb . Append ( b . ToString ( x2 ). ToLower ()); } md5Result = sb . ToString (); File . Delete ( pathDest ); return md5Result ; } } }