GCrypt/GCryptLib/test/Password2Key_CollisionResistance.cpp

#include <GCrypt/Util.h>
#include <GCrypt/Block.h>
#include <GCrypt/Config.h>
#include <unordered_map>
#include <sstream>
#include <iostream>
#include "Catch2.h"

using namespace Leonetienne::GCrypt;

// We can generate passwords by just translating a decimal number to base "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
// So this is just a helper function to generate random passwords
inline std::string Base10_2_X(const unsigned long long int i, const std::string set, unsigned int padding) {
  if (set.length() == 0)
    return ""; // Return empty string, if set is empty. Play stupid games, win stupid prizes.

  std::stringstream ss;

  if (i != 0) {
    {
      unsigned long long int buf = i;
      while (buf != 0) {
        const unsigned long long int mod = buf % set.length();
        buf /= set.length();
        ss << set[(std::size_t)mod];
      }
    }
    {
      const std::string buf = ss.str();
      ss.str("");
      for (long long int i = buf.length() - 1; i >= 0; i--) {
        ss << buf[(std::size_t)i];
      }
    }
  }
  else {
    ss << set[0]; // If i is 0, just pass a null-value. The algorithm would hang otherwise.
  }

  // Add as much null-values to the left as requested.
  if (ss.str().length() < padding) {
    const std::size_t cachedLen = ss.str().length();
    const std::string cachedStr = ss.str();
    ss.str("");
    for (std::size_t i = 0; i < padding - cachedLen; i++) {
      ss << set[0];
    }
    ss << cachedStr;
  }

  return ss.str();
}

// Run a few thousand random passwords through the keygen and see if we'll find a collision.
// This test passing does NOT mean that it's resistant! Maybe good, maybe shit! But if it fails, it's definitely shit.
// Already validated range: Password 0 - 1.000.000
TEST_CASE(__FILE__"/Password to key transformation collision resistance", "[Key extrapolation]") {

  // To test resistence set this to a high number around a million.
  // This will take a LONG while to execute though (about 2.5hrs on my machine), hence why it's set so low.
  constexpr std::size_t NUM_RUN_TESTS = 10;

  std::unordered_map<std::string, std::string> keys; // <key, password>

  // Try NUM_RUN_TESTS passwords
  const std::string charset = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

  for (std::size_t i = 0; i < NUM_RUN_TESTS; i++) {
    // Get password
    const std::string password = Base10_2_X(i, charset, 0);

    // Generate key
    const std::string newKeyBits = Key::FromPassword(password).ToBinaryString();

    // Check if this block is already in our map
    if (keys.find(newKeyBits) != keys.cend()) {
      std::cout << "Collision found between password \""
        << password
        << "\" and \""
        << keys[newKeyBits]
        << "\". The key is \""
        << newKeyBits
        << "\".";

      FAIL();
    }

    // All good? Insert it into our map
    keys[newKeyBits] = password;
  }

  return;
}