/// <summary>
/// Decrypts the encrypted message if it is a symmetrically encrypted
/// message with the passphrase given as argument.
/// </summary>
/// <param name="strPassphrase">The passphrase that was used to encrypt
/// the message</param>
/// <returns>Returns the message that was encrypted. Usually this is
/// an compressed or literal message.</returns>
/// <remarks>No remarks</remarks>
public Message Decrypt(string strPassphrase)
{
if (esKeys.SymKeys.Count == 0)
{
throw new Exception("This message is not symmetrically encrypted. Please provide a keyring rather than a passphrase!");
}
Packet[] pContent = new Packet[0];
Packet[] pReturn = new Packet[0];
IEnumerator ieKeys = esKeys.SymKeys.GetEnumerator();
while (ieKeys.MoveNext())
{
SymSessionKeyPacket skpKey = (SymSessionKeyPacket)ieKeys.Current;
byte[] key = skpKey.S2KSpecifier.GetKey(strPassphrase, CipherHelper.CipherKeySize(skpKey.Algorithm));
try {
SymmetricAlgorithm saAlgo = CipherHelper.CreateSymAlgorithm(skpKey.Algorithm);
pContent = sepData.Decrypt(key, saAlgo);
} catch (System.Security.Cryptography.CryptographicException) {}
if (pContent.Length > 0)
{
pReturn = pContent;
}
}
if (pReturn.Length == 0)
{
throw new System.Security.Cryptography.CryptographicException("Wrong passphrase!");
}
// now we need to look what kind of message was hidden in the
// encrypted data
// it can be either a literal message
LiteralMessage lmLiteral = new LiteralMessage();
try {
int iPos = lmLiteral.ParseMessage(pReturn);
return(lmLiteral);
} catch (Exception) {}
// or an compressed Message
CompressedMessage cmCompressed = new CompressedMessage();
try {
int iPos = cmCompressed.ParseMessage(pReturn);
return(cmCompressed);
} catch (Exception) {}
throw new System.ArgumentException("Encrypted package content is not a valid message!");
}
/// <summary>
/// Decrypts the current encrypted message using the secret keys
/// in skrKeyRing and the given passphrase.
/// </summary>
/// <param name="skrKeyRing">The secret keyring containing all the
/// secret keys know to the sytem.</param>
/// <param name="strPassphrase">The passphrase that was used to
/// encrypt the secret key material in the key that decrypts
/// the message.</param>
/// <returns>Returns the message that was encrypted. Usually this is
/// an compressed or literal message.</returns>
/// <remarks>No remarks</remarks>
public Message Decrypt(SecretKeyRing skrKeyRing, string strPassphrase)
{
TransportableSecretKey tskSecretKey = new TransportableSecretKey();
AsymSessionKeyPacket askpSessionKey = new AsymSessionKeyPacket();
bool bFound = false;
// let's see, if we can find a fitting Sessionkey packet
IEnumerator ieSessionkeys = esKeys.AsymKeys.GetEnumerator();
while (ieSessionkeys.MoveNext())
{
if (!(ieSessionkeys.Current is AsymSessionKeyPacket))
{
throw new Exception("Strange Error!");
}
AsymSessionKeyPacket askpKey = (AsymSessionKeyPacket)ieSessionkeys.Current;
ulong lKeyID = askpKey.KeyID;
TransportableSecretKey tskKey = skrKeyRing.Find(lKeyID);
if (tskKey != null)
{
bFound = true;
tskSecretKey = tskKey;
askpSessionKey = askpKey;
}
}
if (!bFound)
{
throw new Exception("No fitting secret key was found to decrypt the message!");
}
askpSessionKey.DecryptSessionKey(tskSecretKey, strPassphrase);
byte[] bKey = askpSessionKey.SessionKey;
Packet[] pContent = new Packet[0];
try {
SymmetricAlgorithm saAlgo = CipherHelper.CreateSymAlgorithm(askpSessionKey.SymmetricAlgorithm);
pContent = sepData.Decrypt(bKey, saAlgo);
} catch (Exception e) {
throw new System.Exception("Decryption of the Message failed: " + e.Message);
}
// now we need to look what kind of message was hidden in the
// encrypted data
// it can be either a literal message
LiteralMessage lmLiteral = new LiteralMessage();
try {
int iPos = lmLiteral.ParseMessage(pContent);
return(lmLiteral);
} catch (Exception) {}
// or an compressed Message
CompressedMessage cmCompressed = new CompressedMessage();
try {
int iPos = cmCompressed.ParseMessage(pContent);
return(cmCompressed);
} catch (Exception) {}
throw new System.ArgumentException("Encrypted package content is not a valid message!");
}