Gianluca Pacchiella

Selecting random points on a triangle

Gianluca Pacchiella — Sat, 20 Dec 2025 18:11:20 GMT

In this blog post the author explains a couple of ways to choose uniformly a point from a triangle and the first approach that he uses is via the barycentric coordinate: given a triangle identified by the three points \(A\), \(B\) and \(C\)

Generate three random numbers \(\alpha\), \(\beta\) and \(\gamma\) using a uniform distribution from the interval \([0, 1]\)
Normalize the point in such a way that they have sum equal to 1
use \(\alpha A + \beta B + \gamma C\) as the chosen point

The resulting points are not actually uniformly distributed, fact acknowledged by the author itself simply showing a plot of the distribution of the points, my problem is that a plot is not a proof, so this post will try to fix that!

Visual complex analysis: first chapter exercises

Gianluca Pacchiella — Sun, 24 Dec 2023 10:21:08 GMT

"Visual complex analysis" it's a very good book, with really good exercises.

Abstract and symbolic execution notes (with possible application on reverse engineering)

Gianluca Pacchiella — Fri, 26 Aug 2022 13:21:22 GMT

This post will be probably a too ambitious one, since I'm going to write about a very theoretical aspect of computation, in particular the so called abstract interpretation: for now let me just say that this field tries to give the best possible answer to unsolvable characterization of computer programs.

Another point of view that I want to address is the use of this kind of analysis with reverse engineering, since a lot of aspects between these two kind of analysis are shared.

This post will have pretty mathematical formalism but should be readable enough also without a PhD.

Reversing C++, Qt based applications using Ghidra

Gianluca Pacchiella — Fri, 27 May 2022 12:27:43 GMT

This post is going to be too ambitious probably: I want to introduce you to reversing C++ code, applying this knowledge in particular to Qt applications and since we are at it, explaining some ghidra scripting to automate the process.

side channels: power analysis

Gianluca Pacchiella — Sat, 19 Mar 2022 00:00:00 GMT

This is a post in a serie regarding side channels, from the theoretical and pratical point of view; the posts are

introduction on the model of computing devices (to be finished)
using the Chipwhisperer (here)
power analysis (this post)
glitching (to be finished)

side channels: using the chipwhisperer

Gianluca Pacchiella — Wed, 02 Mar 2022 08:43:12 GMT

This is a post in a series regarding side channels, from the theoretical and pratical point of view; the posts are

introduction on the model of computing devices (to be finished)
using the Chipwhisperer (this post)
power analysis (here)
glitching (to be finished)

Reusing old shit: laptop keyboard

Gianluca Pacchiella — Fri, 02 Jul 2021 00:00:00 GMT

Here we are with another experiment in reusing otherwise trash-destined electronics material; in this episode we are going to refurbish a keyboard, from the recovering of the internal "matrix" to the design of the PCB destined as the controller board, to finally reworking of an existing firmware to create a new USB keyboard.

blog migration to Nikola

Gianluca Pacchiella — Thu, 01 Jul 2021 07:27:25 GMT

After running for a couple of years using jekill as a static site generator I decided to switch to nikola for a couple of reasons: first of all because is implemented in python, a language that I know more than ruby and this allows me to improve the platform and customize it more to suite my needs.

Reusing old shit: creating a BSP using Yocto for the Samsung Galaxy S (S5PV210)

Gianluca Pacchiella — Sun, 31 Jan 2021 00:00:00 GMT

In this post I'll describe my esperiments in reusing my old Samsung Galaxy S; don't expected anything sophisticated, it's more a brain dump.

Reusing old shit: lcd screen

Gianluca Pacchiella — Sun, 31 Jan 2021 00:00:00 GMT

It's happened in the past that someone gifted me of very old (and not working anymore) laptops that otherwise would have been thrown in the garbage; my idea for them was of reusing some parts that are more valuable: battery, disks, keyboards, etc...