Add Protocol::SignedMessage struct (not done)

Protocol/src/CMakeLists.txt

@@ -8,3 +8,8 @@ target_sources(Protocol
 		BASE_DIRS include
 		FILES include/protocol/protocol.hxx
 )
+
+target_link_libraries(Protocol
+	PRIVATE
+		sodium
+)

Protocol/src/include/protocol/protocol.hxx

@@ -0,0 +1,23 @@
+#pragma once
+
+#include "sodium/crypto_hash_sha256.h"
+#include "sodium/crypto_sign.h"
+#include <cstdint>
+#include <string>
+namespace Protocol {
+
+struct SignedMessage {
+      unsigned char sender_key_fingerprint[crypto_hash_sha256_BYTES];
+      std::string plaintext;
+      int64_t timestamp;
+      unsigned char sender_key_signature[crypto_sign_BYTES]; // signs fields 1-3
+
+      // Fills the fields and signs the plaintext
+      SignedMessage(unsigned char sender_pub_key[crypto_sign_PUBLICKEYBYTES],
+                    unsigned char sender_priv_key[crypto_sign_SECRETKEYBYTES],
+                    std::string plaintext);
+
+      // TODO: bool isMessageTrusted(std::string pub_key);
+};
+
+} // namespace Protocol

Protocol/src/protocol.cxx

@@ -0,0 +1,38 @@
+#include "sodium/crypto_sign_ed25519.h"
+#include <chrono>
+#include <protocol/protocol.hxx>
+#include <sodium.h>
+
+namespace Protocol {
+
+SignedMessage::SignedMessage(
+    unsigned char sender_pub_key[crypto_sign_PUBLICKEYBYTES],
+    unsigned char sender_priv_key[crypto_sign_SECRETKEYBYTES],
+    std::string plaintext)
+    : plaintext(plaintext) {
+      if (sodium_init() < 0) {
+            throw std::runtime_error("Failed to init sodium!");
+      }
+
+      timestamp = std::chrono::system_clock::now().time_since_epoch().count();
+      crypto_hash_sha256(sender_key_fingerprint, sender_pub_key,
+                         crypto_sign_PUBLICKEYBYTES);
+
+      std::vector<uint8_t> toBeSigned;
+      toBeSigned.reserve(sizeof(sender_key_fingerprint) + plaintext.size() +
+                         sizeof(timestamp));
+
+      toBeSigned.insert(toBeSigned.cend(), sender_key_fingerprint,
+                        sender_key_fingerprint +
+                            sizeof(sender_key_fingerprint));
+      toBeSigned.insert(toBeSigned.cend(), plaintext.data(),
+                        plaintext.data() + plaintext.length());
+      auto timestamp_bytes = reinterpret_cast<const uint8_t *>(&timestamp);
+      toBeSigned.insert(toBeSigned.cend(), timestamp_bytes,
+                        timestamp_bytes + sizeof(timestamp));
+
+      crypto_sign_detached(sender_key_signature, nullptr, toBeSigned.data(),
+                           toBeSigned.size(), sender_priv_key);
+}
+
+} // namespace Protocol