How to secure a marketplace where you could buy and sell digital goods when the blockchain is public ?
How to exchange and encrypt private keys on the blockchain? A decentralized marketplace example.
Guillaume Grandjean - 2023-05-08

While scrolling and reading some articles on Google News, I told myself what a great tool is that all is gathered in one place for the users. No need to crawl the internet, to find information or news! But as always centralisation has also its downside. This platform aims to empower the so much Google against the publishers, that it has become an inevitable source of tension with the revenue generated by the ads. What if the blockchain could help to promote, share, and distribute public and/or private content? This idea led me to propose a concept of a decentralized marketplace where authors could publish and sell their content.

Image 1: An NFT contains metadata, how can we easily access it?
How to access your NFT? A Web2 approach using the best APIs
Guillaume Grandjean - 2022-12-23
Practical example

With an estimated market of more than 11 billion dollars, NFTs are becoming more and more mainstream and widely used. Many applications are developed around them. However, there are different ways to interact with them, some more complicated than others. In this article, we will explain the different ways to retrieve metadata from an NFT. We will detail the “Web 2” approach by comparing different services offering a programming interface (API) for NFTs on the Ethereum Blockchain. Then, we will present an actual example showing how to use these services with an Android and iOS application.

“ According to, there are more than ten thousand different cryptocurrencies.”
The different cryptocurrencies categories 
Leonardo Gomez Mariaca - 2022-11-15
Primary Concept

In our last article, we interested ourselves in the concrete application that Blockchain technologies could offer. We also evoked VeChain, a cryptocurrency notably used for asset traceability. Today, we are going to take the thought further, by looking at the different exciting cryptocurrencies on the market.

« The trust machine », The Economist, 2015.
Blockchain applications
Leonardo Gomez Mariaca - 2022-10-25
Primary Concept

In our previous article, we were interested in the notion of smart contracts and their concrete applications. Today, we will push the thinking a bit further and interest ourselves in the different uses and services that could result from the usage of blockchain technology.

Contract: Legally enforceable convention whereby one or many peoples have to give, do or not do something for someone else.
The smart contracts
Leonardo Gomez Mariaca - 2022-10-10
Primary Concept

In our previous article, we were interested in the security of a decentralized system. Today, we are going to look at one of the first concrete use cases of the blockchain with smart contracts.

If a currency was not secure, the system would collapse.
The security of the Blockchain
Leonardo Gomez Mariaca - 2022-08-01
Primary Concept

In the previous article, we looked at the impact of inflation on the cryptocurrency system. However, one question remains: what about security? In the internet age, where everything is computerized, couldn't a simple hacker get into my computer and steal all my money? Also, couldn't there be a global bug that would wipe out all of this virtual currency?

Since the COVID-19 crisis and the war in Ukraine, inflation is booming.
And what about inflation? 
Leonardo Gomez Mariaca - 2022-07-18
Primary Concept

In the previous article, we discussed the notion of halving, i.e. the fact that miners are rewarded for their work with bitcoins every 10 minutes or so. At the time, we made the following observation: rewarding miners with bitcoins, which have not been available until now, is the equivalent of creating money. And money creation means inflation. 

The blockchain is nothing more than a public series of transactions that mus be "mined", which means controlled and verified.
Blockchain and the idea of Bitcoin
Leonardo Gomez Mariaca - 2022-06-13
Primary Concept

In the last article, we discussed the crucial principle of decentralization on which the functioning of all crypto currencies is based. Here, we will go deeper into the subject around the concept of the blockchain, and in order to do so, we will have to talk about bitcoin. As we saw earlier, the security on which the whole principle of decentralization relies is to make the transaction information public, so that everyone can verify daily that the currency he or she receives is indeed real. In the example we used in the last article, we talked about a large whiteboard on which the transaction should be written down for everyone to see. If we transfer this board to the digital world, we discover the blockchain. Each bitcoin is traced, followed from owner to owner, and it is this information that is kept public to avoid counterfeiting. Of course, the owners are anonymized behind account numbers, but they are still identifiable. To draw a parallel to understand the revolution in the financial system that this implies, let us imagine that the banks published all their transactions on the Internet. Nowadays, this would be an impossible violation of banking secrecy.

The main principle of decentralisation
The decentralization
Leonardo Gomez Mariaca - 2022-06-12
Primary Concept

The first principle to understand and grasp the challenges posed by NFTs, as well as for cryptocurrencies, are decentralised. This is the idea that separates the notion of electronic money, which has long been used by everyone, and a cryptocurrency. Today, our system essentially revolves around banks: when you buy a product in a shop, the price of the product is debited from your account, while the money goes to the account of the seller. The banks have an authoritative role, as they validate the payment, control the smooth running of the transaction, and keep a record of it. This system is centralised around the banks, as there is clearly a form of hierarchy: the banks that handle the transfer of money, and below them, the customers.