absl::string_view override_region) const {

  return fmt::format(SigV4SignatureConstants::SigV4CredentialScopeFormat, short_date,

                     override_region.empty() ? region_ : override_region, service_name_);

}

                                                absl::string_view credential_scope) const {

  auto& crypto_util = Envoy::Common::Crypto::UtilitySingleton::get();

  return fmt::format(

      SigV4SignatureConstants::SigV4StringToSignFormat, SigV4SignatureConstants::SigV4Algorithm,

      long_date, credential_scope,

      Hex::encode(crypto_util.getSha256Digest(Buffer::OwnedImpl(canonical_request))));

}

    const absl::string_view string_to_sign, const absl::string_view override_region) const {

  auto& crypto_util = Envoy::Common::Crypto::UtilitySingleton::get();

  const auto secret_key =

      absl::StrCat(SigV4SignatureConstants::SigV4SignatureVersion, secret_access_key);

  const auto date_key = crypto_util.getSha256Hmac(

      std::vector<uint8_t>(secret_key.begin(), secret_key.end()), short_date);

  const auto region_key =

      crypto_util.getSha256Hmac(date_key, override_region.empty() ? region_ : override_region);

  const auto service_key = crypto_util.getSha256Hmac(region_key, service_name_);

  const auto signing_key =

      crypto_util.getSha256Hmac(service_key, SigV4SignatureConstants::Aws4Request);

  return Hex::encode(crypto_util.getSha256Hmac(signing_key, string_to_sign));

}

    absl::string_view signature) const {

  const auto signed_headers = Utility::joinCanonicalHeaderNames(canonical_headers);

  return fmt::format(SigV4SignatureConstants::SigV4AuthorizationHeaderFormat,

                     SigV4SignatureConstants::SigV4Algorithm,

                     createAuthorizationCredential(access_key_id, credential_scope), signed_headers,

                     signature);

}

absl::string_view SigV4SignerImpl::getAlgorithmString() const {

  return SigV4SignatureConstants::SigV4Algorithm;

}