Author: Daniele Nicassio

Changing the DNS server on Raspberry PI with default Raspbian

Since I’ve been really astonished from the difficulties I’ve had searching for this on the web lately, I’m writing this (really short) blog post hoping to save other people’s time.

If you want to change the DNS server of the default Raspbian installation on a raspberry PI – this probably goes for most of the recent linux distributions too – you just have to edit your /etc/network/interfaces file specifying, under the desired interface, this code:

dns-nameservers 8.8.8.8

Of course replace 8.8.8.8 with your desired DNS server’s IP address.

That’s all.

See you in the next very exciting post!

Agadmatorizer

Hello everyone!

Ok, lately I’ve been approaching the fine art of chess, mostly by watching youtube videos on the matter, and with some playing on lichess.org too. So I couldn’t avoid watching tons of video of the croatian youtuber Agadmator, which is really putting a lot of effort in getting people closer to chess, by publishing one or more videos every day.

So if you’ve been watching some of his videos, you might have noticed that aside the obvious personal contribute he puts in analyzing the games, the rest of the videos is generally just showing the moves and maybe adding some kind-of-predictable comments on them. When the idea came to my mind, I couldn’t help it. I *had to* do algorithmize agadmator.

Long story short, I spent three nights developing a web app which receives a PGN game in input and then generates an (fake) agadmator video for it.

I think it’s quite funny, I’ve really been enjoying the making of it and the end result, however it’s obviously improvable.

The link (for chrome or firefox only, desktop only – sorry for that, didn’t have time to optimize it) is here: Agadmatorizer

Of course I don’t think anyone will really read this, but if someone does, and if agadmator does, I hope you enjoyed this webapp, thank you for reading this post and I’ll see you soon.

Crypto bot

Recently I’ve been following the crypto market, which is very fascinating to me. I’ve subscribed to kraken, a popular exchange and put some money in it. After a service outage in the middle of january, kraken’s team decided to cut the transactions fees for a while, thus I took the opportunity to code and test a from-scratch crypto-trader bot.

I have no time to get into details, also because they are not so much interesting or particularly complex, but I’ll say that it uses a combination of some simple and common algorithms widely used in the study of the financial market. The bot actually works, in the sense that it makes trades on some deterministic rules, but unfortunately it is not clever enough to make profit (even without the fees) and barely breaks even.

Anyway, as always, it’s been very fun and instructive to code, as I had to study and learn how the market behaves, how to handle the market data and how to try to predict trends and accordingly set sell/buy points.

Since I’m not posting the code (yet), here’s its debug window:
cryptobot_best

NotesLearn

I recently bought an alto saxophone. It was quite a while I haven’t seriously been playing an instrument, so I came across a little challenge when it was time to read a music sheet. You know, that thing with a pentagram and some notes of various shapes drawn over it.

Since playing a note on the saxophone is not straightforward as it would be on a piano, I actually had two separate challenges: the first was to recognize a note on the pentagram, the second was to play it well (it means play the correct note steadly for some seconds – and in tune).

So I decided to code a little app to aid me doing so. The app is pretty simple: it shows a (random) note on the pentagram, and then listens to the microphone waiting for a note, identifying the pitch and, after some seconds of playing, says if the played note was correct or not. This app has proven quite useful in the process of improving my reading accuracy and speed, and I guess it might be useful to someone else too.

It’s published here: https://dmnk.cloud/noteslearn.

Technical infos

On the technical side, it is entirely coded using Javascript, and has been a cool challenge to code since it was the first time for me interacting with the microphone data on a web app. It uses some advanced Audio features of HTML5, based on the AudioContext component. Recognizing the pitch was a minor issue, obtained by playing a bit with the FFT of the signal, some other challenges included volume thresholding and octave recognition (less trivial).

In the end, the result is pretty usable for my alto sax, even though it may be less accurate if used with other instruments I didn’t test. The piano version is not perfect, for some notes it needs to repeatedly play the key to make the app recognize it. I guess it should work best with constant-volume-notes kind of instruments, like violin or flute, but as I said it was only fully tested with my alto sax.

KangaMex

Hello everyone! It’s been a while since I last wrote a piece on this blog, since that a lot of things changed, but I still want to share some of my experiences with the world.

I’ll be making some brief posts to track some projects I’ve been working to in these almost 2 years of absence.

This post is about KangaMex, a messaging platform which idea is really simple, yet I didn’t find something like it when I needed it. The app is a delayed messaging service, or a service to send messages which will be delivered only at a specified date and time in the future. You write your message, set the unlock date and time, the recipient’s username, and send it. The recipient will be notified that he/she has an upcoming message, but will not be able to see it until the unlock time has come. Very simple, nice way to send delayed messages.

The app is at mex.kanga.life.

Messaging apps and metadata concerns

I use Telegram. Many use Whatsapp. Others may use other messaging apps.

I’ve heard of debate about whether the security of telegram was really superior to whatsapp and similar arguments for a long time, but recently, a comment about “metadata” got my interest in one of these discussions. The comment pointed out that telegram, which claims to provide a very good security to its users, was leaking a certain amount of metadata.

Metadata is data that describes other data. Meta is a prefix that in most information technology usages means “an underlying definition or description.” Metadata summarizes basic information about data, which can make finding and working with particular instances of data easier.

Actually, the same arguments stands for whatsapp, but this got my attention and I wanted to actually search for some interesting implications. Since telegram is mainly open source and pretty open, we got a number of implementations, and often we have their source code to examine and play with.

Checking out this telegram command line client, it was immediately clear to me that one important piece of metadata which is actually broadcast to all users is the user status.

If you are a telegram (or whatsapp) user, whenever you switch to the app, your user status changes to ‘online’. This information is broadcast to all the users which have your number in their contact list, if you didn’t change the related setting in the preferences of the app. The same happens when you close or background the app, changing your user status to ‘offline’.

Even if the official apps doesn’t let you do that, one of your contacts could certainly write the code to monitor the status of every user regularly, thus building an history of the statuses you’ve been through during the day, collecting a worrying amount of information about you and your habits. Given the amount of messages we’re flooded with in these apps (think about group chats), if you collect this kind of data about someone on his/her primary app of messaging, it’s pretty trivial to derive some sensitive information like sleeping cycles or working hours (not for everyone, but still).

Even worse if you think that when two people are texting, having both contacts on your list means you could probably exploit the data to actually match who is texting to who. This is a bit more trickier to automate, but a finely tuned machine learning algorithm should do it (of course there may be problems with simultaneous conversations and group chats, but it would definitely work at least in some cases).

This isn’t the end of the world, but it is a good insight about a really common security problem of which people using these apps daily are probably completely unaware.

PS. I have of course modified the telegram web app to do this, and even if I’ve spent very little time on this, it actually works. Here’s a screen.

telegram_status_history

 

Code is on github.

Who wants to be millionaire?

You probably know the tv show “Who wants to be a millionaire”. Lately I’ve been invited at the graduation party of a friend, and thought about creating a game for it.

So I decided to create a HTML5 simulation of WWTBAB, complete with webcam support, sounds and introduction video. It has been quite fun, and I’ve been releasing the code on github.

Questions are hardcoded in the index.html file, but it’s trivial to modify them. Recently I’ve added support for images in questions.

I really don’t know if someone can actually make use of it, but who knows?

Just a quick overview about the keys used to control the simulation:

  • [Left arrow] – to skip to next step (video is not skippable by now)
  • [Down arrow] – to unveil the next answer
  • [A,B,C,D] – to highlight the selected answer
  • [Y,N] – when an answer is highlighted, Y makes it correct, N makes it wrong
  • [F] – to switch between the default background or the webcam image
  • [P] – to flash the background to induce some suspance

Github.

Example-link.

A try for a 3D game

Recently I’ve been experimenting a lot with 3D in the browser with Three.js, and although this is my first post about it, there’s a lot more I’m working on about 3D in JS, but it’s involved in my professional work and it’s not time to publish it yet.

Anyway, as usual I like to keep track of my projects here, so I link to this simple game I developed as a joke for a friend some days ago. The game is here, descriptions are in italian but if you don’t understand just click and everything will be fine.