/// <summary>
/// Encrypts bytes asymmetrically via symmetric encryption. Since asymmetric encryption does not support large data sizes, the approach
/// is to generate a symmetric encryption key that is designed for large data sizes, encrypt the data with the symmetric key, encrypt
/// the symmetric key with the asymmetric key, and send the encrypted symmetric key and encrypted data to the same file.
/// </summary>
/// <param name="unencryptedBytes">Unencrypted bytes.</param>
/// <param name="symmetricKeySizeBits">Symmetric key size in bits.</param>
/// <param name="symmetricInitializationVectorSizeBits">Symmetric initialization vector size in bits.</param>
/// <param name="encryptedOutputPath">Encrypted output path.</param>
public void EncryptSymmetrically(byte[] unencryptedBytes, int symmetricKeySizeBits, int symmetricInitializationVectorSizeBits, string encryptedOutputPath)
{
using (AesCryptoServiceProvider aes = new AesCryptoServiceProvider())
{
// generate new symmetric key and initialization vector
aes.KeySize = symmetricKeySizeBits;
aes.BlockSize = symmetricInitializationVectorSizeBits;
aes.GenerateKey();
aes.GenerateIV();
// encrypt the data symmetrically
SymmetricEncryption symmetricEncryption = new SymmetricEncryption(aes.Key, aes.IV);
byte[] encryptedBytes = symmetricEncryption.Encrypt(unencryptedBytes);
// encrypt the symmetric key and initialization vector asymmetrically
byte[] encryptedKeyBytes = Encrypt(aes.Key);
byte[] encryptedIVBytes = Encrypt(aes.IV);
// write the encrypted output file
using (FileStream encryptedOutputFile = new FileStream(encryptedOutputPath, FileMode.Create, FileAccess.Write))
{
// ...encrypted symmetric key length and bytes
byte[] encryptedKeyBytesLength = BitConverter.GetBytes(encryptedKeyBytes.Length);
encryptedOutputFile.Write(encryptedKeyBytesLength, 0, encryptedKeyBytesLength.Length);
encryptedOutputFile.Write(encryptedKeyBytes, 0, encryptedKeyBytes.Length);
// ...encrypted initialization vector length and bytes
byte[] encryptedIVBytesLength = BitConverter.GetBytes(encryptedIVBytes.Length);
encryptedOutputFile.Write(encryptedIVBytesLength, 0, encryptedIVBytesLength.Length);
encryptedOutputFile.Write(encryptedIVBytes, 0, encryptedIVBytes.Length);
// ...encrypted bytes
encryptedOutputFile.Write(encryptedBytes, 0, encryptedBytes.Length);
}
}
}
/// <summary>
/// Encrypts bytes asymmetrically via symmetric encryption. Since asymmetric encryption does not support large data sizes, the approach
/// is to generate a symmetric encryption key that is designed for large data sizes, encrypt the data with the symmetric key, encrypt
/// the symmetric key with the asymmetric key, and send everything to output.
/// </summary>
/// <param name="unencryptedBytes">Unencrypted bytes.</param>
/// <param name="symmetricKeySizeBits">Symmetric key size in bits.</param>
/// <param name="symmetricInitializationVectorSizeBits">Symmetric initialization vector size in bits.</param>
/// <param name="encryptedOutputStream">Encrypted output stream.</param>
/// <param name="cancellationToken">Cancellation token.</param>
public Task EnvelopeAsync(byte[] unencryptedBytes, int symmetricKeySizeBits, int symmetricInitializationVectorSizeBits, Stream encryptedOutputStream, CancellationToken cancellationToken)
{
using (AesCryptoServiceProvider aes = new AesCryptoServiceProvider())
{
// generate new symmetric key and initialization vector
aes.KeySize = symmetricKeySizeBits;
aes.BlockSize = symmetricInitializationVectorSizeBits;
aes.GenerateKey();
aes.GenerateIV();
// encrypt the data symmetrically
SymmetricEncryption symmetricEncryption = new SymmetricEncryption(aes.Key, aes.IV);
byte[] encryptedBytes = symmetricEncryption.Encrypt(unencryptedBytes);
// encrypt the symmetric key and initialization vector asymmetrically
byte[] encryptedKeyBytes = Encrypt(aes.Key);
byte[] encryptedIVBytes = Encrypt(aes.IV);
// write the encrypted output stream
// ...encrypted symmetric key length and bytes
byte[] encryptedKeyBytesLength = BitConverter.GetBytes(encryptedKeyBytes.Length);
encryptedOutputStream.Write(encryptedKeyBytesLength, 0, encryptedKeyBytesLength.Length);
encryptedOutputStream.Write(encryptedKeyBytes, 0, encryptedKeyBytes.Length);
// ...encrypted initialization vector length and bytes
byte[] encryptedIVBytesLength = BitConverter.GetBytes(encryptedIVBytes.Length);
encryptedOutputStream.Write(encryptedIVBytesLength, 0, encryptedIVBytesLength.Length);
encryptedOutputStream.Write(encryptedIVBytes, 0, encryptedIVBytes.Length);
// ...encrypted bytes
encryptedOutputStream.Write(encryptedBytes, 0, encryptedBytes.Length);
}
return(Task.CompletedTask);
}