My little Bitcoin investment & mining experience

I do not count the time I looked at Bitcoin in the past since about 2011-2012. Every time I started thinking about mining there was an investment to do (like GPU, then ASIC) and I never trust enough this money to make this investment. So as a consequence I never jump into this techno by the past, more than to understand how it works and learn.

Now Bitcoin in reaching some unexpected peaks ( > 15,000€ ) and it really looks like a bubble everyone is talking about, so as a mad man, I through it was the perfect time to start playing with this money. Trust me, as a guy who started investing in Internet technologies in 2001, you may never follow me on such decision !

Starting playing with this was an interesting learning opportunity, so this post will relate this experience and the different things I found in the bitcoin ecosystem.

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SpringBoot and JWT security

When creating an API you can manage a “session” with a JWT Json Web Tokens ensuring the user has login previously.

This post explains how JWT is working and how to implement it with SpringBoot using user identity stored in a Database.

This is based on a real implementation and is the sum of lots of search on Internet to make it correctly working.

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IoT introduction

This IoT class is an introduction to IoT and LPWAN, it has been made to be a 2x2h teaching session for engineer school students. This class has been given to I.S.I.M.A. school in Clermont-Ferrand in 2017. This class has been completed by 2 more hours on the backend part for IoT by Daniel Petisme. It has been followed by three industrial conferences.

The content of my class had the following slides (in French):

Introduce why IoT is a revolution compared to M2M and why service matter. Introduce the different phases of a connected object design and the involved technologies. Introduce the challenge, from the technical stand point to the business model considerations.

Introduce the LPWAn technologies, presenting Sigfox and LoRaWan solutions.

 

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The Sigfox radio protocol

Sigfox phase decoding

Sigfox is a LPWAn communication technology and network dedicated to IoT. The specificity of this solution is related to the LPWAn caracteristics : communicating Low Power (25mW) and Wide Area (60km).

This is possible thanks to particular radio characteristics and modulation. This post will describes how it works at radio level and protocol level.

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Sigfox Radio Signal Analyzer

Sigfox just released publicly its Radio Signal Analyzer tool. This is a tool for the device & module maker to prepare the P1 certification : basically it checks the radio signal shape, power… and tell you if you are following the requirements.

The tool have to be used with the SIGFOX SDR dongle provided with the SNEK tool.

The software solution can be downloaded here : https://support.sigfox.com/downloads/sigfoxradiosignalanalyzer.iso

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SpringBoot webservices full example

SpringBoot is a really efficient framework for creating webservices and much more. For this reason I’m using it to design my backend applications.

This framework is also well referenced on Internet and many people are downloading it and using it. All of this sounds really good and you will see you can make a webservice in less than 5 minutes following the many examples existing on Internet. As usually in this kind of technology once you have made the classical HelloWorld and university classical practices you have a lot of difficulties to make your first real program coupling different simple use-cases. So As I spent a couple of hours searching solution on Internet, this post will give you a full example of a project getting data from a MongoDB instance to provide a simple webservice.

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The Sigfox Network Emulator Kit

Sigfox is a LPWA network using the free radio frequency to communicate. There radio frequencies are changing in the different zone (Europe, America, Asia…) When you are developing a device you need to test it but you are not authorized to use all these frequency from the country you are.

The Sigfox emulator is a solution for this : it allows to directly connect your device and analyze the transmission whatever the frequency you are using is. The Sigfox emulator kit is an SDR dongle with a Sigfox software for understanding, decoding the sigfox signals.

You can wire your transmitter to this receiver to not emit the signal over-the-air and legally use a non authorized frequency in your country. When you are using an authorized frequency you can simply communicate over the air.

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Gcc – wrap a function in a closed archive

Here is the situation : you have a function in an archive but you do not have the source code. And you would like to change the behavior of this function or intercept the call to this function.

This is possible with gcc and the -Wl,-wrap linker options. Thanks to this option you can create a new function starting by __wrap_ followed by the function name. This function will be called instead of the original one. In the function you can decide to call the original function by using its name starting by __real_

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