x25519 key exchange

src/commonTest/kotlin/KeysTest.kt

@@ -83,4 +83,26 @@ class KeysTest {
         }
     }
 
+    @Test
+    fun keyExchangeTest() = runTest {
+        initCrypto()
+        val ske = SafeKeyExchange()
+        val cke = SafeKeyExchange()
+
+        val clientSessionKey = cke.clientSessionKey(ske.publicKey)
+        val serverSessionKey = ske.serverSessionKey(cke.publicKey)
+
+        val src = "Hello, Dolly!"
+        assertEquals(src, serverSessionKey.decryptString(clientSessionKey.encrypt(src)))
+        assertEquals(src, serverSessionKey.decryptString(clientSessionKey.encrypt(src)))
+        assertEquals(src, serverSessionKey.decryptString(clientSessionKey.encrypt(src)))
+        assertEquals(src, serverSessionKey.decryptString(clientSessionKey.encrypt(src)))
+
+        assertEquals(src, clientSessionKey.decryptString(serverSessionKey.encrypt(src)))
+        assertEquals(src, clientSessionKey.decryptString(serverSessionKey.encrypt(src)))
+        assertEquals(src, clientSessionKey.decryptString(serverSessionKey.encrypt(src)))
+        assertEquals(src, clientSessionKey.decryptString(serverSessionKey.encrypt(src)))
+
+    }
+
 }