diff --git a/presence/implementation/ldt.cc b/presence/implementation/ldt.cc
index 68039b8a..8b38fc25 100644
--- a/presence/implementation/ldt.cc
+++ b/presence/implementation/ldt.cc
@@ -29,6 +29,9 @@ namespace nearby {
 namespace presence {
 
 namespace {
+// NP LDT library says that 0 is returned when `NpLdtCreate()` fails.
+constexpr NpLdtHandle kInvalidLdtHandle = static_cast<NpLdtHandle>(0);
+
 template <class T>
 T FromStringView(absl::string_view data) {
   T result{
@@ -54,7 +57,7 @@ NpLdtAesCipherHandle AesCreateCipher(NpLdtAes128Key key) {
 
 int32_t AesCloseCipher(NpLdtAesCipherHandle handle) {
   AesContext* ctx = reinterpret_cast<AesContext*>(handle);
-  free(ctx);
+  delete ctx;
   return 0;
 }
 
@@ -70,6 +73,16 @@ void AesDecrypt(NpLdtAesCipherHandle handle, NpLdtAesBlock* block) {
 
 }  // namespace
 
+LdtEncryptor::LdtEncryptor(LdtEncryptor&& other)
+    : ldt_handle_(other.ldt_handle_) {
+  other.ldt_handle_ = kInvalidLdtHandle;
+}
+LdtEncryptor::~LdtEncryptor() {
+  if (ldt_handle_ != kInvalidLdtHandle) {
+    NpLdtClose(ldt_handle_);
+  }
+}
+
 absl::StatusOr<LdtEncryptor> LdtEncryptor::Create(
     absl::string_view key_seed, absl::string_view known_hmac) {
   NpLdtHandle handle =
@@ -79,7 +92,7 @@ absl::StatusOr<LdtEncryptor> LdtEncryptor::Create(
                    .decrypt = AesDecrypt},
                   FromStringView<NpLdtKeySeed>(key_seed),
                   FromStringView<NpMetadataKeyHmac>(known_hmac));
-  if (handle == nullptr) {
+  if (handle == kInvalidLdtHandle) {
     return absl::UnavailableError("Failed to create LDT encryptor");
   }
 
diff --git a/presence/implementation/ldt.h b/presence/implementation/ldt.h
index 22ab45a3..f64519c0 100644
--- a/presence/implementation/ldt.h
+++ b/presence/implementation/ldt.h
@@ -29,19 +29,13 @@ namespace presence {
 class LdtEncryptor {
  public:
   LdtEncryptor(const LdtEncryptor&) = delete;
-  LdtEncryptor(LdtEncryptor&& other) : ldt_handle_(other.ldt_handle_) {
-    other.ldt_handle_ = nullptr;
-  }
+  LdtEncryptor(LdtEncryptor&& other);
   LdtEncryptor& operator=(const LdtEncryptor&) = delete;
   LdtEncryptor& operator=(LdtEncryptor&& other) {
     std::swap(ldt_handle_, other.ldt_handle_);
     return *this;
   }
-  ~LdtEncryptor() {
-    if (ldt_handle_ != nullptr) {
-      NpLdtClose(ldt_handle_);
-    }
-  }
+  ~LdtEncryptor();
 
   // Creates an instance of `LdtEncryptor`.
   // `key_seed` is used to generate LDT encryption and decryption keys.
diff --git a/presence/implementation/np_ldt.h b/presence/implementation/np_ldt.h
index 070628d1..30c4c5a6 100644
--- a/presence/implementation/np_ldt.h
+++ b/presence/implementation/np_ldt.h
@@ -33,7 +33,7 @@ extern "C" {
 // decrypting advertisements from a known origin
 
 // Handle for accessing the rust ldt implementation apis
-typedef void* NpLdtHandle;
+typedef uint64_t NpLdtHandle;
 
 // Key material from the Nearby Presence credential from which keys will be
 // derived.