using System; using System.IO; using System.Security.Cryptography; // // Sample encrypt/decrypt functions // Parameter checks and error handling // are ommited for better readability // @author:Ashwin Kumar // Date : 12/3/2008 public class AESEncryptionUtility { static int Main(string[] args) { if (args.Length < 2) { Console.WriteLine("Usage: AESEncryptionUtility infile outFile"); return 1; } string infile = args[0]; string outfile = args[1]; //string keyfile = args[2]; //var key = File.ReadAllBytes(keyfile); Encrypt(infile,outfile,"test"); Decrypt(outfile,"_decrypted"+infile,"test"); return 0; } // 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(); } } 