--- components/web_package/signed_web_bundles/signed_web_bundle_utils.cc.orig	2026-09-25 15:26:43 UTC
+++ components/web_package/signed_web_bundles/signed_web_bundle_utils.cc
@@ -5,18 +5,37 @@
 #include "components/web_package/signed_web_bundles/signed_web_bundle_utils.h"
 
 #include <cstdint>
-#include <vector>
 
-#include "components/web_package/signed_web_bundles/rust/signed_web_bundles_rust.h"
+#include "base/containers/extend.h"
+#include "base/containers/span.h"
+#include "base/containers/span_writer.h"
 
 namespace web_package {
 
+namespace {
+
+void AddItemToPayload(std::vector<uint8_t>& payload,
+                      base::span<const uint8_t> item) {
+  // Each item that is part of the payload is prefixed with its length encoded
+  // as a 64 bit unsigned integer.
+  std::array<uint8_t, sizeof(uint64_t)> length;
+  auto writer = base::SpanWriter(base::span(length));
+  CHECK(writer.WriteU64BigEndian(item.size()));
+
+  base::Extend(payload, base::span(length));
+  base::Extend(payload, item);
+}
+
+}  // namespace
+
 std::vector<uint8_t> CreateSignaturePayload(
     const SignedWebBundleSignatureData& data) {
-  auto payload_rust = signed_web_bundles::rust::create_signature_payload(
-      data.unsigned_web_bundle_hash, data.integrity_block_cbor,
-      data.attributes_cbor);
-  return std::vector<uint8_t>(payload_rust.begin(), payload_rust.end());
+  std::vector<uint8_t> payload;
+  AddItemToPayload(payload, data.unsigned_web_bundle_hash);
+  AddItemToPayload(payload, data.integrity_block_cbor);
+  AddItemToPayload(payload, data.attributes_cbor);
+
+  return payload;
 }
 
 }  // namespace web_package