/**
* * generate password scheme either a) during initialization or b) after successful login
*
* @param hpwd
* @param positions
* @param password
*/
private static void generateScheme(BigInteger hpwd, Position[] positions, String password) {
/* generate new random polynomial */
Polynomial newPoly = Polynomial.getRandomPolynomial(Constants.M - 1, hpwd);
/* generate new R value and persist */
Generator.R = Generator.getRandomInteger(Generator.BIT_LENGTH);
LoginHandler.getPreferences().put(Constants.PREF_R, Generator.R.toString());
/* reinitialize P and G functions with new R value */
initFunctions(password);
/* generate new Instruction Table and write to file */
InstructionTable iTable = InstructionTable.generateInstructionTable(positions, newPoly);
iTable.writeToFile(Constants.INSTRUCTION_TABLE_FILE_PATH);
}
/**
* * extracts hardened password from features and password
*
* @param features
* @param password
* @return hardened password
*/
private static BigInteger extractHardenedPwd(long[] features, String password) {
List<Point> points = new LinkedList<Point>();
InstructionTable iTable = InstructionTable.loadTable(Constants.INSTRUCTION_TABLE_FILE_PATH);
for (int i = 0; i < features.length; i++) {
int index = iTable.get(i).getIndex();
BigInteger x = null, y = null;
switch (InstructionTable.getPosition(features[i], i)) {
case ALPHA:
case BOTH:
x = p_function.execute(2 * index);
y = iTable.get(i).getAlpha().subtract(g_function.execute(2 * index)).mod(Constants.Q);
break;
case BETA:
x = p_function.execute(2 * index + 1);
y = iTable.get(i).getBeta().subtract(g_function.execute(2 * index + 1)).mod(Constants.Q);
break;
}
points.add(new Point(x, y));
}
BigInteger hpwd = Polynomial.generateZerothCoefficientFromPoints(points);
return hpwd;
}