I am having trouble getting to processes (running on different machines)
to agree on a value using their Diffie-Hellman keys.
Do the different DH objects need the same RandomNumber objects? I send
their public keys over the network and try to Agree() them with the
opposite private key (as in the crypto++ example). However, this always
fails. The only thing I can see that's different is that I am using a
different PRNG object (obviously, as they're on different machines!).
Also can you explain what this does (well, I know what memset does), and
more importantly why the specific values:
Line 198 in validat2.cpp
memset(val1.begin(), 0x10, val1.size());
memset(val2.begin(), 0x11, val2.size());
The code I'm using (or a snippet of as I don't want to swamp the list)
is:
string data;
// Setup the pseudo random number generator
AutoSeededRandomPool *arng = new AutoSeededRandomPool;
RandomNumberGenerator &rng = *dynamic_cast<RandomNumberGenerator *>
(arng);
// declare a diffie-hellman object
DH dh (rng, 128);
// declare the local validation and public-private key pair
SecByteBlock local_validate (dh.AgreedValueLength ());
SecByteBlock local_public_key (dh.PublicKeyLength ());
SecByteBlock local_private_key (dh.PrivateKeyLength ());
// clear the validation object
fill (local_validate.begin (), local_validate.end (), 0x11);
// generate the public-private key pair
dh.GenerateKeyPair (rng, local_private_key, local_public_key);
delete arng;
// encode the local public key to a hexed-string
StringSource (local_public_key, true, new HexEncoder (new StringSink
(data)));
cout << "Local public key: " << data << endl;
// connect to the server
JClientSocket c ("eeyore", 50000);
// send the local public key
c << data;
// clear the string
data.clear ();
// receive the server's public key
c >> data;
cout << "Foreign public key: " << data << endl;
// decode the hexed-string to the foreign public key
SecByteBlock foreign_public_key (dh.PublicKeyLength ());
StringSource (foreign_public_key, true, new HexDecoder (new StringSink
(data)));
// clear the string
data.clear ();
// agreement method with the local private and the foreign public key
if (!dh.Agree (local_validate, local_private_key, foreign_public_key)) {
cout << "Key agreement failed." << endl;
return 1;
}
The server has similar code (this is the client)
Regards
Jim
--
James Vanns BSc (Hons) MCP
Linux Systems Administrator
Senior Software Engineer (Linux / C & C++)
Canterbury Christ Church University College
Public Key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x24045370
