void EncodedFSM::preProcess( const FSM& fsm ) {
std::cout << "[EncodedFSM]: Preproccessing FSM ..." << std::endl;
size_t k = _secretKeyPtr->k();
size_t lambda = _secretKeyPtr->lambda();
auto states = fsm.states();
std::map<size_t, PolyRingMatrixPtr> stateSecretKeys;
// secret start key is already generated
stateSecretKeys[0] = make_unique<PolyRingMatrix>( *_secretKeyPtr->start() );
// create new random key for every state except start state
std::cout << "[EncodedFSM]: Creating encoded state keys ..." << std::endl;
for ( size_t stateID = 1; stateID < fsm.numStates(); ++stateID ) {
// key should be Z^n -> 1 polynomial in ring setting
auto stateKey = PolyRingMatrix{1, 1, lambda, k};
stateKey.uniformInit();
stateSecretKeys[stateID] = make_unique<PolyRingMatrix>( stateKey );
}
/**
* Encode transitions using public matrices and secret start and terminal
* states.
*/
auto G = GTrapdoor{k, lambda};
auto transitions = fsm.transitions();
std::cout << "[EncodedFSM]: Creating encoded transitions ..." << std::endl;
for ( size_t stateID = 0; stateID < fsm.numStates(); ++stateID ) {
auto transition = transitions[stateID];
// retrieve state keys
auto currentStateKey = make_unique<PolyRingMatrix>( *stateSecretKeys[stateID] );
auto stateKeyFor0 = make_unique<PolyRingMatrix>( *stateSecretKeys[transition.nextStateFor0()]);
auto stateKeyFor1 = make_unique<PolyRingMatrix>( *stateSecretKeys[transition.nextStateFor1()] );
// sample error
auto e0 = _secretKeyPtr->buildTernaryTempMatrix( k, 1 );
auto e1 = _secretKeyPtr->buildTernaryTempMatrix( k, 1 );
// encode transitions
auto t0 = *_secretKeyPtr->A0() * *currentStateKey + e0 + G * *stateKeyFor0;
auto t1 = *_secretKeyPtr->A1() * *currentStateKey + e1 + G * *stateKeyFor1;
_transitions.push_back( make_unique<PolyRingMatrix>( t0 ) );
_transitions.push_back( make_unique<PolyRingMatrix>( t1 ) );
// generate error for terminal transition
auto et = _secretKeyPtr->buildTernaryTempMatrix( k, 1 );
// encode terminal transition
if ( states[stateID].acceptState() ) {
auto tt = *_secretKeyPtr->At() * *currentStateKey + et + G *
*_secretKeyPtr->accept();
_acceptTransitions.push_back( make_unique<PolyRingMatrix>( tt ) );
} else {
auto tt = *_secretKeyPtr->At() * *currentStateKey + et + G *
*_secretKeyPtr->reject();
_rejectTransitions.push_back( make_unique<PolyRingMatrix>( tt ) );
}
}
std::cout << "[EncodedFSM]: DONE preprocessing" << std::endl;
}
