using System;
using System.IO;
using System.Security.Cryptography;

namespace WpfApplication19
{
    // 


    //    This sample code is provided "AS IS" with no warranties,

    //    and confers no rights. 

    // 

    //    ATTENTION: This sample is designed to be more of a

    //    tutorial rather than something you can copy and paste in

    //    the production code! 

    // 




    

    // 

    // Sample encrypt/decrypt functions 

    // Parameter checks and error handling

    // are ommited for better readability 

    // 


    public class EncDec
    {
        // Encrypt a byte array into a byte array using a key and an IV 

        public static byte[] Encrypt(byte[] clearData, byte[] Key, byte[] IV)
        {
            // Create a MemoryStream to accept the encrypted bytes 

            MemoryStream ms = new MemoryStream();

            // Create a symmetric algorithm. 

            // We are going to use Rijndael because it is strong and

            // available on all platforms. 

            // You can use other algorithms, to do so substitute the

            // next line with something like 

            //      TripleDES alg = TripleDES.Create(); 

            Rijndael alg = Rijndael.Create();

            // Now set the key and the IV. 

            // We need the IV (Initialization Vector) because

            // the algorithm is operating in its default 

            // mode called CBC (Cipher Block Chaining).

            // The IV is XORed with the first block (8 byte) 

            // of the data before it is encrypted, and then each

            // encrypted block is XORed with the 

            // following block of plaintext.

            // This is done to make encryption more secure. 


            // There is also a mode called ECB which does not need an IV,

            // but it is much less secure. 

            alg.Key = Key;
            alg.IV = IV;

            // Create a CryptoStream through which we are going to be

            // pumping our data. 

            // CryptoStreamMode.Write means that we are going to be

            // writing data to the stream and the output will be written

            // in the MemoryStream we have provided. 

            CryptoStream cs = new CryptoStream(ms,
               alg.CreateEncryptor(), CryptoStreamMode.Write);

            // Write the data and make it do the encryption 

            cs.Write(clearData, 0, clearData.Length);

            // Close the crypto stream (or do FlushFinalBlock). 

            // This will tell it that we have done our encryption and

            // there is no more data coming in, 

            // and it is now a good time to apply the padding and

            // finalize the encryption process. 

            cs.Close();

            // Now get the encrypted data from the MemoryStream.

            // Some people make a mistake of using GetBuffer() here,

            // which is not the right way. 

            byte[] encryptedData = ms.ToArray();

            return encryptedData;
        }

        // Encrypt a string into a string using a password 

        //    Uses Encrypt(byte[], byte[], byte[]) 


        public static string Encrypt(string clearText, string Password)
        {
            // First we need to turn the input string into a byte array. 

            byte[] clearBytes =
              System.Text.Encoding.Unicode.GetBytes(clearText);

            // Then, we need to turn the password into Key and IV 

            // We are using salt to make it harder to guess our key

            // using a dictionary attack - 

            // trying to guess a password by enumerating all possible words. 

            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,
                new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 
            0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76});

            // Now get the key/IV and do the encryption using the

            // function that accepts byte arrays. 

            // Using PasswordDeriveBytes object we are first getting

            // 32 bytes for the Key 

            // (the default Rijndael key length is 256bit = 32bytes)

            // and then 16 bytes for the IV. 

            // IV should always be the block size, which is by default

            // 16 bytes (128 bit) for Rijndael. 

            // If you are using DES/TripleDES/RC2 the block size is

            // 8 bytes and so should be the IV size. 

            // You can also read KeySize/BlockSize properties off

            // the algorithm to find out the sizes. 

            byte[] encryptedData = Encrypt(clearBytes,
                     pdb.GetBytes(32), pdb.GetBytes(16));

            // Now we need to turn the resulting byte array into a string. 

            // A common mistake would be to use an Encoding class for that.

            //It does not work because not all byte values can be

            // represented by characters. 

            // We are going to be using Base64 encoding that is designed

            //exactly for what we are trying to do. 

            return Convert.ToBase64String(encryptedData);

        }

        // Encrypt bytes into bytes using a password 

        //    Uses Encrypt(byte[], byte[], byte[]) 


        public static byte[] Encrypt(byte[] clearData, string Password)
        {
            // We need to turn the password into Key and IV. 

            // We are using salt to make it harder to guess our key

            // using a dictionary attack - 

            // trying to guess a password by enumerating all possible words. 

            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,
                new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 
            0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76});

            // Now get the key/IV and do the encryption using the function

            // that accepts byte arrays. 

            // Using PasswordDeriveBytes object we are first getting

            // 32 bytes for the Key 

            // (the default Rijndael key length is 256bit = 32bytes)

            // and then 16 bytes for the IV. 

            // IV should always be the block size, which is by default

            // 16 bytes (128 bit) for Rijndael. 

            // If you are using DES/TripleDES/RC2 the block size is 8

            // bytes and so should be the IV size. 

            // You can also read KeySize/BlockSize properties off the

            // algorithm to find out the sizes. 

            return Encrypt(clearData, pdb.GetBytes(32), pdb.GetBytes(16));

        }

        // Encrypt a file into another file using a password 

        public static void Encrypt(string fileIn,
                    string fileOut, string Password) 
    { 

        // First we are going to open the file streams 

        FileStream fsIn = new FileStream(fileIn, 
            FileMode.Open, FileAccess.Read); 
        FileStream fsOut = new FileStream(fileOut, 
            FileMode.OpenOrCreate, FileAccess.Write); 

        // Then we are going to derive a Key and an IV from the

        // Password and create an algorithm 

        PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password, 
            new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 
            0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76}); 

        Rijndael alg = Rijndael.Create(); 
        alg.Key = pdb.GetBytes(32); 
        alg.IV = pdb.GetBytes(16); 

        // Now create a crypto stream through which we are going

        // to be pumping data. 

        // Our fileOut is going to be receiving the encrypted bytes. 

        CryptoStream cs = new CryptoStream(fsOut, 
            alg.CreateEncryptor(), CryptoStreamMode.Write); 

        // Now will will initialize a buffer and will be processing

        // the input file in chunks. 

        // This is done to avoid reading the whole file (which can

        // be huge) into memory. 

        int bufferLen = 4096; 
        byte[] buffer = new byte[bufferLen]; 
        int bytesRead; 

        do { 
            // read a chunk of data from the input file 

            bytesRead = fsIn.Read(buffer, 0, bufferLen); 

            // encrypt it 

            cs.Write(buffer, 0, bytesRead); 
        } while(bytesRead != 0); 

        // close everything 


        // this will also close the unrelying fsOut stream

        cs.Close(); 
        fsIn.Close();     
    }

        // Decrypt a byte array into a byte array using a key and an IV 

        public static byte[] Decrypt(byte[] cipherData,
                                    byte[] Key, byte[] IV)
        {
            // Create a MemoryStream that is going to accept the

            // decrypted bytes 

            MemoryStream ms = new MemoryStream();

            // Create a symmetric algorithm. 

            // We are going to use Rijndael because it is strong and

            // available on all platforms. 

            // You can use other algorithms, to do so substitute the next

            // line with something like 

            //     TripleDES alg = TripleDES.Create(); 

            Rijndael alg = Rijndael.Create();

            // Now set the key and the IV. 

            // We need the IV (Initialization Vector) because the algorithm

            // is operating in its default 

            // mode called CBC (Cipher Block Chaining). The IV is XORed with

            // the first block (8 byte) 

            // of the data after it is decrypted, and then each decrypted

            // block is XORed with the previous 

            // cipher block. This is done to make encryption more secure. 

            // There is also a mode called ECB which does not need an IV,

            // but it is much less secure. 

            alg.Key = Key;
            alg.IV = IV;

            // Create a CryptoStream through which we are going to be

            // pumping our data. 

            // CryptoStreamMode.Write means that we are going to be

            // writing data to the stream 

            // and the output will be written in the MemoryStream

            // we have provided. 

            CryptoStream cs = new CryptoStream(ms,
                alg.CreateDecryptor(), CryptoStreamMode.Write);

            // Write the data and make it do the decryption 

            cs.Write(cipherData, 0, cipherData.Length);

            // Close the crypto stream (or do FlushFinalBlock). 

            // This will tell it that we have done our decryption

            // and there is no more data coming in, 

            // and it is now a good time to remove the padding

            // and finalize the decryption process. 

            cs.Close();

            // Now get the decrypted data from the MemoryStream. 

            // Some people make a mistake of using GetBuffer() here,

            // which is not the right way. 

            byte[] decryptedData = ms.ToArray();

            return decryptedData;
        }

        // Decrypt a string into a string using a password 

        //    Uses Decrypt(byte[], byte[], byte[]) 


        public static string Decrypt(string cipherText, string Password)
        {
            // First we need to turn the input string into a byte array. 

            // We presume that Base64 encoding was used 

            byte[] cipherBytes = Convert.FromBase64String(cipherText);

            // Then, we need to turn the password into Key and IV 

            // We are using salt to make it harder to guess our key

            // using a dictionary attack - 

            // trying to guess a password by enumerating all possible words. 

            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,
                new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 
            0x64, 0x76, 0x65, 0x64, 0x65, 0x76});

            // Now get the key/IV and do the decryption using

            // the function that accepts byte arrays. 

            // Using PasswordDeriveBytes object we are first

            // getting 32 bytes for the Key 

            // (the default Rijndael key length is 256bit = 32bytes)

            // and then 16 bytes for the IV. 

            // IV should always be the block size, which is by

            // default 16 bytes (128 bit) for Rijndael. 

            // If you are using DES/TripleDES/RC2 the block size is

            // 8 bytes and so should be the IV size. 

            // You can also read KeySize/BlockSize properties off

            // the algorithm to find out the sizes. 

            byte[] decryptedData = Decrypt(cipherBytes,
                pdb.GetBytes(32), pdb.GetBytes(16));

            // Now we need to turn the resulting byte array into a string. 

            // A common mistake would be to use an Encoding class for that.

            // It does not work 

            // because not all byte values can be represented by characters. 

            // We are going to be using Base64 encoding that is 

            // designed exactly for what we are trying to do. 

            return System.Text.Encoding.Unicode.GetString(decryptedData);
        }

        // Decrypt bytes into bytes using a password 

        //    Uses Decrypt(byte[], byte[], byte[]) 


        public static byte[] Decrypt(byte[] cipherData, string Password)
        {
            // We need to turn the password into Key and IV. 

            // We are using salt to make it harder to guess our key

            // using a dictionary attack - 

            // trying to guess a password by enumerating all possible words. 

            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,
                new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 
            0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76});

            // Now get the key/IV and do the Decryption using the 

            //function that accepts byte arrays. 

            // Using PasswordDeriveBytes object we are first getting

            // 32 bytes for the Key 

            // (the default Rijndael key length is 256bit = 32bytes)

            // and then 16 bytes for the IV. 

            // IV should always be the block size, which is by default

            // 16 bytes (128 bit) for Rijndael. 

            // If you are using DES/TripleDES/RC2 the block size is

            // 8 bytes and so should be the IV size. 


            // You can also read KeySize/BlockSize properties off the

            // algorithm to find out the sizes. 

            return Decrypt(cipherData, pdb.GetBytes(32), pdb.GetBytes(16));
        }

        // Decrypt a file into another file using a password 

        public static void Decrypt(string fileIn,
                    string fileOut, string Password) 
    { 
    
        // First we are going to open the file streams 

        FileStream fsIn = new FileStream(fileIn,
                    FileMode.Open, FileAccess.Read); 
        FileStream fsOut = new FileStream(fileOut,
                    FileMode.OpenOrCreate, FileAccess.Write); 
  
        // Then we are going to derive a Key and an IV from

        // the Password and create an algorithm 

        PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password, 
            new byte[] {0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 
            0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76}); 
        Rijndael alg = Rijndael.Create(); 

        alg.Key = pdb.GetBytes(32); 
        alg.IV = pdb.GetBytes(16); 

        // Now create a crypto stream through which we are going

        // to be pumping data. 

        // Our fileOut is going to be receiving the Decrypted bytes. 

        CryptoStream cs = new CryptoStream(fsOut, 
            alg.CreateDecryptor(), CryptoStreamMode.Write); 
  
        // Now will will initialize a buffer and will be 

        // processing the input file in chunks. 

        // This is done to avoid reading the whole file (which can be

        // huge) into memory. 

        int bufferLen = 4096;
        byte[] buffer = new byte[bufferLen];
        int bytesRead; 

        do { 
            // read a chunk of data from the input file 

            bytesRead = fsIn.Read(buffer, 0, bufferLen); 

            // Decrypt it 

            cs.Write(buffer, 0, bytesRead); 

        } while(bytesRead != 0); 

        // close everything 

        cs.Close(); // this will also close the unrelying fsOut stream 

        fsIn.Close();     
        }
    }


}
