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/*
* (C) 2009-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/botan.h>
#include <botan/dh.h>
#include <botan/pubkey.h>
using namespace Botan;
#include <iostream>
#include <memory>
int main()
{
Botan::LibraryInitializer init;
try
{
AutoSeeded_RNG rng;
// Alice and Bob agree on a DH domain to use
DL_Group shared_domain("modp/ietf/1024");
// Alice creates a DH key and sends (the public part) to Bob
DH_PrivateKey private_a(rng, shared_domain);
// Alice sends to Bob her public key:
MemoryVector<byte> public_a = private_a.public_value();
// Bob creates a key with a matching group
DH_PrivateKey private_b(rng, shared_domain);
// Bob sends his public key to Alice
MemoryVector<byte> public_b = private_b.public_value();
PK_Key_Agreement ka1(private_a, "KDF2(SHA-1)");
PK_Key_Agreement ka2(private_b, "KDF2(SHA-1)");
/*
* Preferably, include some salt or parameter that binds this key
* generation to the current session (for instance a session
* identifier, if guaranteed unique, would be a good choice). Or
* anything else that both sides can agree on that will never
* repeat.
*/
const std::string ka_salt = "alice and bob agree on a key";
SymmetricKey alice_key = ka1.derive_key(32, public_b, ka_salt);
SymmetricKey bob_key = ka2.derive_key(32, public_a, ka_salt);
if(alice_key == bob_key)
{
std::cout << "The two keys matched, everything worked\n";
std::cout << "The shared key was: " << alice_key.as_string() << "\n";
}
else
{
std::cout << "The two keys didn't match! Hmmm...\n";
std::cout << "Alice's key was: " << alice_key.as_string() << "\n";
std::cout << "Bob's key was: " << bob_key.as_string() << "\n";
}
// Now use the shared key for encryption or MACing or whatever
}
catch(std::exception& e)
{
std::cout << e.what() << std::endl;
return 1;
}
return 0;
}
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