KeyExchange.cs

public static void KeyExchange()
{
    String publicKeyPem = PlayerPrefs.GetString("clientPublicKey");
    if(String.IsNullOrEmpty(publicKeyPem))
    {
        throw new PlayerPrefsItemNotFoundException("clientPublicKey");
    }
    String EcPublicKeyDerHexStr = EcPemtoDer(publicKeyPem, "public");
    String serializedHttpBody = JsonConvert.SerializeObject(EcPublicKeyDerHexStr);

    var (headers, jsonResponseText) = RequestHandler.Post("xxx.azurewebsites.com/api/KeyExchange"), null, false, serializedHttpBody);

    KeyExchangeDto kexDto = new KeyExchangeDto();
    try
    {
        kexDto = JsonConvert.DeserializeObject<KeyExchangeDto>(jsonResponseText);
    }
    catch(JsonSerializationException ex)
    {
        Debug.Log(ex.Message);
    }
    
    // the data that retrieve from the server
    String keyId = kexDto.KeyId;
    String salt = kexDto.Salt;
    String serverPublicKey = kexDto.ServerPublicKey;
    PlayerPrefs.SetString("keyId", keyId);
    PlayerPrefs.SetString("salt", salt);
    PlayerPrefs.SetString("serverPublicKey", serverPublicKey);
}