Added support for SafeKeyExchange serialization/deserialization and associated tests.

src/commonTest/kotlin/KeysTest.kt

@@ -221,6 +221,26 @@ class KeysTest {
 
     }
 
+    @Test
+    fun keyExchangeSerializationTest() = runTest {
+        initCrypto()
+        val ske = SafeKeyExchange()
+        val packedExchange = pack(ske)
+
+        val cke = SafeKeyExchange()
+        val clientSessionKey = cke.clientSessionKey(ske.publicKey)
+
+        val restoredExchange = unpack<SafeKeyExchange>(packedExchange)
+        assertEquals(ske.publicKey, restoredExchange.publicKey)
+
+        val serverSessionKey = restoredExchange.serverSessionKey(cke.publicKey)
+
+        val src = "Hello after restore!"
+        assertEquals(src, serverSessionKey.decryptString(clientSessionKey.encrypt(src)))
+        assertEquals(src, clientSessionKey.decryptString(serverSessionKey.encrypt(src)))
+        assertContentEquals(clientSessionKey.sessionTag, serverSessionKey.sessionTag)
+    }
+
     @Test
     fun asymmetricKeyTest() = runTest {
         initCrypto()