using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Security.Cryptography;
namespace TrainingCenterSystem.Utils
{
public class StringEncryption
{
public static string EncryptString(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);
}
public static byte[] Encrypt(byte[] clearData, byte[] Key, byte[] IV)
{
// Create a MemoryStream that is going 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;
}
private static byte[] EncryptString(byte[] clearText, byte[] Key, byte[] IV)
{
MemoryStream ms = new MemoryStream();
Rijndael alg = Rijndael.Create();
alg.Key = Key;
alg.IV = IV;
CryptoStream cs = new CryptoStream(ms, alg.CreateEncryptor(), CryptoStreamMode.Write);
cs.Write(clearText, 0, clearText.Length);
cs.Close();
byte[] encryptedData = ms.ToArray();
return encryptedData;
}
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.Replace(" ","+"));
// 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();
}
}
}
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