public static byte[] DecryptMessage(byte[] message, KeyPair key)
{
const int VERSION_LENGTH = 1;
const int NONCE_LENGTH = 24;
const int SENDER_KEY_LENGTH = 32;
const int RECIP_VERIFIER_LENGTH = 16;
var version = ArrayHelpers.SubArray(message, 0, VERSION_LENGTH)[0];
byte[] ret;
switch (version)
{
case 0x00:
var nonce = ArrayHelpers.SubArray(message, 1, NONCE_LENGTH);
var senderKey = ArrayHelpers.SubArray(message, 25, SENDER_KEY_LENGTH);
var verifier = ArrayHelpers.SubArray(message, 57, RECIP_VERIFIER_LENGTH);
var encrypted = ArrayHelpers.SubArray(message, 73);
//check the verifier, to make sure that the message is for this KeyPair before going on
var recipVarifier = GenericHash.Hash(ArrayHelpers.ConcatArrays(nonce, key.PublicKey), null, 16);
if (Utilities.ByteArrayCompare(verifier, recipVarifier))
{
throw new CryptographicException("Invalid verifier; message not encrypted for this key.");
}
var decrypted = PublicKeyBox.Open(encrypted, nonce, key.PrivateKey, senderKey);
ret = decrypted;
break;
default:
//TODO: Unsupported version
throw new NotImplementedException();
}
return(ret);
}
public static byte[] EncryptMessage(byte[] message, string toId)
{
//generate an ephemeral key to encrypt this with
var key = PublicKeyBox.GenerateKeyPair();
//decode the recip ID
var recip = Base58Check.Base58CheckEncoding.Decode(toId);
//Check to make sure that the ID version is supported
if (recip[0] != ID_VERSION)
{
throw new CryptographicException("Invalid ID Format.");
}
var nonce = SodiumCore.GetRandomBytes(24);
var encrypted = PublicKeyBox.Create(message, nonce, key.PrivateKey, ArrayHelpers.SubArray(recip, 1));
var recipVerifier = GenericHash.Hash(ArrayHelpers.ConcatArrays(nonce, key.PublicKey), null, 16);
var version = new byte[] { 0x00 };
var final = ArrayHelpers.ConcatArrays(version, nonce, key.PublicKey, recipVerifier, encrypted);
return(final);
}
public static string EncodePublicKey(byte[] publicKey)
{
var version = new byte[] { 0x0A };
return(Base58Check.Base58CheckEncoding.Encode(ArrayHelpers.ConcatArrays(version, publicKey)));
}