//Decrypt the envelope and return the output array.
public byte[] DecryptEnvelope()
{
//Create the RSAWrapper from a string representation of its name.
rsaAlgorithm = new RSAWrapper(rsaName);
//Initialize the RSA algorithm key.
rsaAlgorithm.RSAalg.FromXmlString(rsaKey);
//Create the CipherMode from a string representation of its name.
cipherMode = HelperExtensions.StringToCipherMode(cipherName);
symmetricAlgorithm = HelperExtensions.StringToSymAlg(symmetricAlgorithmName, cipherMode, cipherName);
symmetricAlgorithm.algorithm.IV = initializationVector;
symmetricAlgorithm.algorithm.Key = rsaAlgorithm.RSADecrypt(DigitalEnvelopeEncrypted.EncryptedSymmetricKey, true);
return(symmetricAlgorithm.Decrypt(DigitalEnvelopeEncrypted.EncryptedMessage));
}
//Return a SymmetricAlgorithmWrapper object given the symmetric algorithm name (including key size), CipherMode and cipher name.
public static SymmetricAlgorithmWrapper StringToSymAlg(string input, CipherMode cipherMode, string cipherName)
{
SymmetricAlgorithmWrapper symmetricAlgorithm = input switch
{
"AES 128" => new SymmetricAlgorithmWrapper("Aes", cipherName, 128, cipherMode),
"AES 192" => new SymmetricAlgorithmWrapper("Aes", cipherName, 192, cipherMode),
"AES 256" => new SymmetricAlgorithmWrapper("Aes", cipherName, 256, cipherMode),
"TripleDES 128" => new SymmetricAlgorithmWrapper("TripleDES", cipherName, 128, cipherMode),
"TripleDES 192" => new SymmetricAlgorithmWrapper("TripleDES", cipherName, 192, cipherMode),
_ => new SymmetricAlgorithmWrapper("Aes", cipherName, 128, cipherMode),
};
return(symmetricAlgorithm);
}
//Create a DigitalEnvelope instance which will be used to create an envelope.
public DigitalEnvelope(SymmetricAlgorithmWrapper SYMAlgorithm, RSAWrapper rsaAlgorithm, string inputFilePath)
{
this.symmetricAlgorithm = SYMAlgorithm;
this.rsaAlgorithm = rsaAlgorithm;
LoadInputFile(inputFilePath);
}