/// <summary>
/// Adds an asymmetrically encrypted session key to the ESK
/// Sequence.
/// </summary>
/// <param name="askpKey">An asymmetrical session key packet
/// that is to be added to the ESKSequence.</param>
/// <remarks>No remarks</remarks>
public void AddAsymSessionKey(AsymSessionKeyPacket askpKey)
{
bUpdated = true;
alAsymKeys.Add(askpKey);
}
/// <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!");
}
private static ESKSequence CreateESKSequence(ArrayList alKeys, AsymActions aaAction, SymAlgorithms saAlgo, byte[] bSymKey)
{
IEnumerator ieKeys = alKeys.GetEnumerator();
ESKSequence esksReturn = new ESKSequence();
while (ieKeys.MoveNext()) {
TransportablePublicKey tpkKey = (TransportablePublicKey)ieKeys.Current;
PublicKeyPacket pkpKey = tpkKey.FindKey(aaAction);
if (pkpKey == null)
throw new Exception("Could not find subkey fitting to the selected action. Concerned Key: " + tpkKey.PrimaryUserID);
AsymSessionKeyPacket skpKey = new AsymSessionKeyPacket();
skpKey.KeyID = pkpKey.KeyID;
skpKey.PublicAlgorithm = pkpKey.Algorithm;
skpKey.SymmetricAlgorithm = saAlgo;
skpKey.SessionKey = bSymKey;
skpKey.EncryptSessionKey(pkpKey);
esksReturn.AddAsymSessionKey(skpKey);
}
return esksReturn;
}
/// <summary>
/// Adds an asymmetrically encrypted session key to the ESK
/// Sequence.
/// </summary>
/// <param name="askpKey">An asymmetrical session key packet
/// that is to be added to the ESKSequence.</param>
/// <remarks>No remarks</remarks>
public void AddAsymSessionKey(AsymSessionKeyPacket askpKey)
{
bUpdated = true;
alAsymKeys.Add(askpKey);
}
/// <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!");
}
