private void OnInfoButtonClick(object sender, EventArgs e)
{
using (PackageFactory keyFactory = new PackageFactory(_keyFilePath, _container.Authority))
{
using (FormInfo frmInfo = new FormInfo())
{
frmInfo.SetInfo(keyFactory.KeyInfo());
frmInfo.ShowDialog(this);
}
}
}
/// <remarks>
/// This method demonstrates using a PackageFactory and StreamCipher class to
/// both encrypt a file, and optionally sign the message with an SHA512 HMAC.
/// See the StreamCipher and StreamMac documentation for more examples.
/// </remarks>
private void Encrypt()
{
CipherDescription keyHeader;
KeyParams keyParam;
try
{
byte[] keyId = null;
byte[] extKey = null;
// get the keyheader and key material from the key file
using (PackageFactory keyFactory = new PackageFactory(_keyFilePath, _container.Authority))
{
// get the key info
PackageInfo pki = keyFactory.KeyInfo();
if (!keyFactory.AccessScope.Equals(KeyScope.Creator))
{
MessageBox.Show(keyFactory.LastError);
return;
}
keyId = (byte[])keyFactory.NextKey(out keyHeader, out keyParam, out extKey).Clone();
}
// offset start position is base header + Mac size
int hdrOffset = MessageHeader.GetHeaderSize + keyHeader.MacSize;
// with this constructor, the StreamCipher class creates the cryptographic
// engine using the description in the CipherDescription.
// The (cipher and) engine are destroyed in the cipherstream dispose
using (StreamCipher cstrm = new StreamCipher(true, keyHeader, keyParam))
{
using (FileStream inStream = new FileStream(_inputPath, FileMode.Open, FileAccess.Read))
{
using (FileStream outStream = new FileStream(_outputPath, FileMode.Create, FileAccess.ReadWrite))
{
// start at an output offset equal to the message header + MAC length
outStream.Seek(hdrOffset, SeekOrigin.Begin);
// use a percentage counter
cstrm.ProgressPercent += new StreamCipher.ProgressDelegate(OnProgressPercent);
// initialize internals
cstrm.Initialize(inStream, outStream);
// write the encrypted output to file
cstrm.Write();
// write the key id to the header
MessageHeader.SetKeyId(outStream, keyId);
// write the encrypted file extension
MessageHeader.SetExtension(outStream, MessageHeader.GetEncryptedExtension(Path.GetExtension(_inputPath), extKey));
// if this is a signing key, calculate the mac
if (keyHeader.MacSize > 0)
{
// Get the mac for the encrypted file; Mac engine is SHA512 by default,
// configurable via the CipherDescription MacSize and MacEngine members.
// This is where you would select and initialize the correct Digest via the
// CipherDescription members, and initialize the corresponding digest.
// For expedience, this example is fixed on the default SHA512.
// An optional progress event is available in the StreamMac class.
using (StreamMac mstrm = new StreamMac(new SHA512HMAC(keyParam.IKM)))
{
// seek to end of header
outStream.Seek(hdrOffset, SeekOrigin.Begin);
// initialize mac stream
mstrm.Initialize(outStream);
// get the hash; specify offset and adjusted size
byte[] hash = mstrm.ComputeMac(outStream.Length - hdrOffset, hdrOffset);
// write the keyed hash value to the message header
MessageHeader.SetMessageMac(outStream, hash);
}
}
}
}
}
// destroy the key
keyParam.Dispose();
}
catch (Exception ex)
{
if (File.Exists(_outputPath))
File.Delete(_outputPath);
string message = ex.Message == null ? "" : ex.Message;
MessageBox.Show("An error occured, the file could not be encrypted! " + message);
}
finally
{
Invoke(new MethodInvoker(() => { Reset(); }));
}
}