1 files changed, 75 insertions, 0 deletions
diff --git a/tde2e/td/e2e/CheckSharedSecret.cpp b/tde2e/td/e2e/CheckSharedSecret.cpp
new file mode 100644
index 000000000..032237419
--- /dev/null
+++ b/tde2e/td/e2e/CheckSharedSecret.cpp
@@ -0,0 +1,75 @@
+//
+// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2025
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+#include "td/e2e/CheckSharedSecret.h"
+
+#include "td/utils/crypto.h"
+
+#include <utility>
+
+namespace tde2e_core {
+
+CheckSharedSecret CheckSharedSecret::create() {
+  CheckSharedSecret result;
+  result.nonce_ = generate_nonce();
+  td::sha256(result.nonce_.as_slice(), result.nonce_hash_.as_mutable_slice());
+  return result;
+}
+
+td::UInt256 CheckSharedSecret::commit_nonce() const {
+  return nonce_hash_;
+}
+
+td::Result<td::UInt256> CheckSharedSecret::reveal_nonce() const {
+  if (!o_other_nonce_hash_) {
+    return td::Status::Error("Cannot reveal nonce before other nonce hash is known");
+  }
+  return nonce_;
+}
+
+td::Status CheckSharedSecret::recive_commit_nonce(const td::UInt256 &other_nonce_hash) {
+  if (o_other_nonce_hash_) {
+    return td::Status::Error("Already received other nonce hash");
+  }
+  o_other_nonce_hash_ = other_nonce_hash;
+  return td::Status::OK();
+}
+
+td::Status CheckSharedSecret::receive_reveal_nonce(const td::UInt256 &other_nonce) {
+  if (!o_other_nonce_hash_) {
+    return td::Status::Error("Cannot  receive nonce before nonce hash");
+  }
+  td::UInt256 expected_nonce_hash;
+  td::sha256(other_nonce.as_slice(), expected_nonce_hash.as_mutable_slice());
+  if (expected_nonce_hash != *o_other_nonce_hash_) {
+    return td::Status::Error("Other nonce hash is different from the expected one");
+  }
+  o_other_nonce_ = other_nonce;
+  return td::Status::OK();
+}
+
+td::Result<td::UInt256> CheckSharedSecret::finalize_hash(td::Slice shared_secret) const {
+  if (!o_other_nonce_) {
+    return td::Status::Error("Cannot calculate hash before other nonce is known");
+  }
+  td::UInt256 a = nonce_;
+  td::UInt256 b = *o_other_nonce_;
+  if (b < a) {
+    std::swap(a, b);
+  }
+  td::Sha256State state;
+  state.init();
+  state.feed(shared_secret);
+  state.feed(a.as_slice());
+  state.feed(b.as_slice());
+
+  td::UInt256 hash;
+  state.extract(hash.as_mutable_slice());
+
+  return hash;
+}
+
+}  // namespace tde2e_core