public void SetMessageKeys(ECPublicKey senderEphemeral, MessageKeys messageKeys)
{
var chainAndIndex = GetReceiverChain(senderEphemeral);
var chain = chainAndIndex.Item1;
var messageKeyStructure = new Chain.MessageKey {
cipherKey = messageKeys.CipherKey,
macKey = messageKeys.MacKey,
index = messageKeys.Counter,
iv = messageKeys.Iv
};
chain.messageKeys.Add(messageKeyStructure);
}
private byte[] GetPlaintext(UInt32 version, MessageKeys messageKeys, byte[] cipherText)
{
try
{
ICryptoTransform cipher;
if(version >= 3)
{
cipher = GetCipher(messageKeys.CipherKey, messageKeys.Iv);
}
else
{
cipher = GetCipher(messageKeys.CipherKey, messageKeys.Counter);
}
return cipher.TransformFinalBlock(cipherText, 0, cipherText.Length);
}
catch(Exception e)
{
throw new InvalidMessageException(e);
}
}
public MessageKeys RemoveMessageKeys(ECPublicKey senderEphemeral, UInt32 counter)
{
Tuple<Chain, UInt32> chainAndIndex = GetReceiverChain(senderEphemeral);
Chain chain = chainAndIndex.Item1;
if(chain == null)
{
return null;
}
MessageKeys result = null;
// TODO: Check~
foreach(var mK in chain.messageKeys)
{
if(mK.index == counter)
{
result = new MessageKeys(mK.cipherKey, mK.macKey, mK.iv, mK.index);
chain.messageKeys.Remove(mK);
break;
}
}
return result;
}
private byte[] GetCiphertext(UInt32 version, MessageKeys messageKeys, byte[] plaintext)
{
try
{
ICryptoTransform cipher;
if(version >= 3)
{
cipher = GetCipher(messageKeys.CipherKey, messageKeys.Iv);
}
else
{
cipher = GetCipher(messageKeys.CipherKey, messageKeys.Counter);
}
return cipher.TransformFinalBlock(plaintext, 0, plaintext.Length);
}
catch(Exception e)
{
throw new InvalidOperationException("Assertion error", e);
}
}
