tink password-based encryption.cpp

   // ==================================================================================================
   // First, given a password, generate a key, as per https://stackoverflow.com/a/52196373/758986
   // aka perform "key stretching"
   const std::string Password = "Password";
   const std::string Salt     = "1234";
   std::string       Key;
   Key.resize(32);
   // https://crypto.stackexchange.com/questions/35423/appropriate-scrypt-parameters-when-generating-an-scrypt-hash?newreg=c73ca93cedae4729b07a9ab776e4904b
   const int ScryptResult = EVP_PBE_scrypt(Password.data(),
                                           Password.size(),
                                           reinterpret_cast<const uint8_t *>(Salt.data()),
                                           Salt.size(),
                                           1 << 20,                 // N => 128Nr bytes, 2Nr rounds
                                           16,                      // r
                                           1,                       // uint64_t p,
                                           5ull * std::gibi::num,   // max_mem
                                           reinterpret_cast<uint8_t *>(Key.data()),
                                           Key.size());
   std::cout << "Scrypt return: " << ScryptResult << "\nKey:\n" << Key << std::endl;

   // ==================================================================================================
   // Encrypt
   ctu::StatusOr<std::unique_ptr<ct::Aead>> StatusOrAead = ct::subtle::AesGcmBoringSsl::New(Key);
   if(StatusOrAead.ok() == false) {
      std::cout << StatusOrAead.status().error_message() << std::endl;
      return 0;
   }
   std::unique_ptr<ct::Aead>  Aead               = std::move(StatusOrAead.ValueOrDie());
   const std::string          PlainText          = "Hello world!";
   ctu::StatusOr<std::string> StatusOrCiphertext = Aead->Encrypt(PlainText, {});
   if(StatusOrAead.ok() == false) {
      std::cout << StatusOrCiphertext.status().error_message() << std::endl;
      return 0;
   }
   const std::string Ciphertext = std::move(StatusOrCiphertext.ValueOrDie());


   // ==================================================================================================
   // Decrypt
   ctu::StatusOr<std::unique_ptr<ct::Aead>> StatusOrAead2 = ct::subtle::AesGcmBoringSsl::New(Key);
   if(StatusOrAead2.ok() == false) {
      std::cout << StatusOrAead2.status().error_message() << std::endl;
      return 0;
   }
   std::unique_ptr<ct::Aead>  Aead2             = std::move(StatusOrAead2.ValueOrDie());
   ctu::StatusOr<std::string> StatusOrPlainText = Aead->Decrypt(Ciphertext, {});
   if(StatusOrPlainText.ok() == false) {
      std::cout << StatusOrPlainText.status().error_message() << std::endl;
      return 0;
   }
   std::cout << "Initial plaintext: " << PlainText << "\n"
             << "Restored plaintext: " << StatusOrPlainText.ValueOrDie() << std::endl;