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- using System;
- using System.Collections.Generic;
- using System.IO;
- using System.Linq;
- using System.Security.Cryptography;
- using System.Text;
- using System.Threading.Tasks;
- namespace BoxyBot.Util
- {
- public static class StringCipher
- {
- // This constant is used to determine the keysize of the encryption algorithm in bits.
- // We divide this by 8 within the code below to get the equivalent number of bytes.
- private const int Keysize = 256;
- // This constant determines the number of iterations for the password bytes generation function.
- private const int DerivationIterations = 1000;
- public static string Encrypt(string plainText, string passPhrase)
- {
- // Salt and IV is randomly generated each time, but is preprended to encrypted cipher text
- // so that the same Salt and IV values can be used when decrypting.
- var saltStringBytes = Generate256BitsOfRandomEntropy();
- var ivStringBytes = Generate256BitsOfRandomEntropy();
- var plainTextBytes = Encoding.UTF8.GetBytes(plainText);
- using (var password = new Rfc2898DeriveBytes(passPhrase, saltStringBytes, DerivationIterations))
- {
- var keyBytes = password.GetBytes(Keysize / 8);
- using (var symmetricKey = new RijndaelManaged())
- {
- symmetricKey.BlockSize = 256;
- symmetricKey.Mode = CipherMode.CBC;
- symmetricKey.Padding = PaddingMode.PKCS7;
- using (var encryptor = symmetricKey.CreateEncryptor(keyBytes, ivStringBytes))
- {
- using (var memoryStream = new MemoryStream())
- {
- using (var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
- {
- cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
- cryptoStream.FlushFinalBlock();
- // Create the final bytes as a concatenation of the random salt bytes, the random iv bytes and the cipher bytes.
- var cipherTextBytes = saltStringBytes;
- cipherTextBytes = cipherTextBytes.Concat(ivStringBytes).ToArray();
- cipherTextBytes = cipherTextBytes.Concat(memoryStream.ToArray()).ToArray();
- memoryStream.Close();
- cryptoStream.Close();
- return Convert.ToBase64String(cipherTextBytes);
- }
- }
- }
- }
- }
- }
- public static string Decrypt(string cipherText, string passPhrase)
- {
- // Get the complete stream of bytes that represent:
- // [32 bytes of Salt] + [32 bytes of IV] + [n bytes of CipherText]
- var cipherTextBytesWithSaltAndIv = Convert.FromBase64String(cipherText);
- // Get the saltbytes by extracting the first 32 bytes from the supplied cipherText bytes.
- var saltStringBytes = cipherTextBytesWithSaltAndIv.Take(Keysize / 8).ToArray();
- // Get the IV bytes by extracting the next 32 bytes from the supplied cipherText bytes.
- var ivStringBytes = cipherTextBytesWithSaltAndIv.Skip(Keysize / 8).Take(Keysize / 8).ToArray();
- // Get the actual cipher text bytes by removing the first 64 bytes from the cipherText string.
- var cipherTextBytes = cipherTextBytesWithSaltAndIv.Skip((Keysize / 8) * 2).Take(cipherTextBytesWithSaltAndIv.Length - ((Keysize / 8) * 2)).ToArray();
- using (var password = new Rfc2898DeriveBytes(passPhrase, saltStringBytes, DerivationIterations))
- {
- var keyBytes = password.GetBytes(Keysize / 8);
- using (var symmetricKey = new RijndaelManaged())
- {
- symmetricKey.BlockSize = 256;
- symmetricKey.Mode = CipherMode.CBC;
- symmetricKey.Padding = PaddingMode.PKCS7;
- using (var decryptor = symmetricKey.CreateDecryptor(keyBytes, ivStringBytes))
- {
- using (var memoryStream = new MemoryStream(cipherTextBytes))
- {
- using (var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
- {
- var plainTextBytes = new byte[cipherTextBytes.Length];
- var decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
- memoryStream.Close();
- cryptoStream.Close();
- return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
- }
- }
- }
- }
- }
- }
- private static byte[] Generate256BitsOfRandomEntropy()
- {
- var randomBytes = new byte[32]; // 32 Bytes will give us 256 bits.
- using (var rngCsp = new RNGCryptoServiceProvider())
- {
- // Fill the array with cryptographically secure random bytes.
- rngCsp.GetBytes(randomBytes);
- }
- return randomBytes;
- }
- }
- }
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