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  • What is blockchain technology or DLT (Distributed Ledger Technology)?

    Blockchain is a technology used for the keeping and the transmission of information in a decentralized network, meaning without an entity that controls the system. Blockchain facilitates the transfer of data using consensus algorithms and cryptographic hashing functions. Basically blockchain is an open distributed ledger that can records interactions between 2 parties, efficiently and in a verifiable and permanent way. A blockchain network is tipically managed collectively by a peer to peer network of individuals. Invented in 2008, blockchain original purpose was to serve as a public ledger for the cryptocurrency Bitcoin. Blockchain allows the transfer of value while continually keeping track of any information sent and received. The main advantages revolve around decentralization, security, immutability, and transparency. Due to its characteristics, blockchain technologies have limitless potential applications, the most know one being crypto currencies.

  • What is Bitcoin?

    Bitcoin is the first digital asset ever created, and was the first network using blockchain technology. The unit of account of Bitcoin is a bitcoin (BTC), and alternative unit of account is satoshi (sat), 1 sat = 0.00000001 bitcoins. Bitcoin works as a decentralized digital currency operating on a network where participants can virtually access, buy, send and receive BTC, without the need of a single administrator. The innovation with Bitcoin is that users of this technology can exchange value with anyone else using the Bitcoin network, requiring only an internet connection. Indeed, Bitcoin is the first digital currency that solves the double spending problem, a major flaw of digital tokens, without the need of a trusted third party or central server. The Bitcoin ledger keeps track of every single transaction that has occurred on the network. The system works by continually verifying the authenticity of transactions by comparing the information between the different network nodes using a consensus algorithm. Transactions are verified using cryptography and recorded in a public distributed ledger called a blockchain. Throughout the years, Bitcoin success has grown and is now regularly subject to popular interest, mainly due to its high price volatility. Despite that, more and more individuals and businesses are accepting Bitcoin as a mean of payment.

  • What is Ethereum?

    Ethereum is an open software platform and foundation created in 2013 by Vitalik Buterin and first released in 2015. Using blockchain technology, Ethereum is an open source platform to be used in decentralized applications (Dapps). The protocol that was created using blockchain technology allows developers to build decentralized applications and use smart contract development, a smart contract being a digital contract that will execute itself under predefined conditions. The Ethereum foundation has issued a cryptocurrency called ether (ETH) which fuels the network. Miners, people maintaining the network, earn ETH, and it is used to pay for services and transaction fees by application developers. It is the second most popular digital asset by market capitalization. The simplicity and efficiency of the ether token has made it a standard for numerous application hence, most of tokens created using smart contracts are based on Ethereum tokens. Like Bitcoin, the validity of each ether is provided by a blockchain, which is a continuously growing list of records, called blocks, which are linked and secured using cryptography. However, the main difference between Bitcoin and Ethereum is that Ethereum network is programmable, meaning that developers can modify it to develop new kinds of applications.

  • What is Nimiq?

    Nimiq is a simple, secure and censorship-resistant payment protocol, native to the web. Being a browser-first blockchain, Nimiq makes paying as simple as browsing a website: no apps, no plugins, completely installation-free. Anyone with an up-to-date browser can join Nimiq's payment network directly, pay and accept payments without having to install software or rely on unnecessary middlemen. It works on all devices that come with a browser, from desktops to mobile phones. $NIM is the currency that is transacted within Nimiq as a store and transfer of value. Uncompromised decentralization, open source and a strong focus on usability are Nimiq’s commitments, bringing crypto and blockchain technology to where the user already is: online. As a blockchain and payment protocol native to the web, Nimiq is offering any form of payment, be it online, in a shop, or between friends, as long as the device is connected. Nimiq will transition to it's own new proof-of-stake algorithm "Albatross" soon. This original blockchain consensus algorithm is co-created by Nimiq and able to achieve sub-second transaction confirmations with peak performances of over 1000 transactions per second.

  • What is cryptocurrency?

    A cryptocurrency (or crypto currency) is a digital asset designed to work as a medium of exchange that uses strong cryptography to secure financial transactions, control the creation of additional units, and verify the transfer of assets. Cryptocurrencies use decentralized control as opposed to centralized digital currency and central banking systems. The decentralized control of each cryptocurrency works through distributed ledger technology, typically a blockchain, that serves as a public financial transaction database. Released in 2008, Bitcoin is considered to be the first decentralized crypto currency. The model of Bitcoin has since been used for thousands of other crypto currencies, they all are different but observe the characteristics of cypto currencies : - no need for a central authority, the network is maintained through distributed consensus - the ledger keep track of cryptocurrency units and their ownership - he system defines how and when to create new units - Cryptography is used to prove ownership - A transaction statement can only be issued by an intentity proving the current ownership of the concerned units Cryptocurrencies are a financial and monetary application using blockchain technology proposing an alternative way to organize financial exchanges between parties.

  • What is sharing economy?

    An economic system in which assets or services are shared between individuals, it represents a way to distribute goods services that differs from traditionnal corporation models. In a centralized corporate model the company is hiring staff to sell to customers, in sharing economy individuals tend to make other individuals use their posessions like cars or homes. Sharing economy works as a peer to peer network where users benefit from each other in exchange of compensation. We can observe two different kinds of sharing economy network organisation; a commercial business model model in which a company provides a service to be used by suppliers and customers and non profit initiative where goods and services are provided for free or for a low subscription fee.

  • What is a cryptoccurency wallet?

    A wallet is a virtual storage software where digital assets can be stored. It uses the blockchain of the digital assets supported to store, send and receive digital assets. Each wallet is unique and has its own private address which correspond to the ID of the user on a particular blockchain network. The public key is used to send or receive digital assets.

  • What is Magna Numeris

    Magna Numeris is a start-up company based in Paris, France that develops and operates softwares and digital products. The company is registered at 10 rue de Penthièvre, Paris, France. The first product released is this one, a P2P marketplace dedicated to crypto currency user for face to face transactions.

  • Who is responsible?

    Cartam is providing a service that allows users to connect and trade between them. Magna Numeris SAS and Cartam team are not responsible for any misuse of the app that will cause any loss of value or any problem related to users wallet's funds. Any blockchain transaction (technology used by the Cartam app) cannot be undone, and it is on the users to set up the transaction details correctly. Never communicate your private key, make sure you enter the right blockchain address and the right amount when a transaction is to be done.

  • What is Magna Numeris’s mission?

    Magna Numeris mission is to offer a new solution for the peer-to-peer economy, using blockchain technology. We intend to build and operate several technological products and create a strong community of users.

  • What is Magna Numeris’s vison?

    Magna Numeris vision is to become one of the few first blockchain mobile application that achieves mass adoption. We aim to build a major peer-to-peer platform in France and in Europe.

  • How does it work?

    User connects on the application, using Touch or Face ID to log in. He can then go on the map, click on another user's announcement to see the trade proposed. If he is interested in making the trade, he can contact the other user using the transaction assistant to complete the transaction. Once the transaction is processed, each user rates the transaction.

  • What can I do with my Cartam account ?

    My Cartam account allows me to browse the ads posted on the marketplace, to post ads of items I wish to sell and to interact with ads posted on the marketplace if I am interested into buying the product displayed. Cartam does not provide a blockchain wallet, to exchange crypto currency, you need to have a functional blockchain wallet of your own.

  • How can I contact other users? put in contact cryptocurrency users for face to face transactions using a message system. You need to create account to access this feature. Once your account is created you can contact another user by going on an ad posted by another user and type your message in the text box. He will receive a notification letting him know that someone contacted him about his offer an a chat will be created. You can anytime access your chats with others in your profile page.

  • How can I modify my account information ?

    On your profile page, you can click on the « edit profile » button that will lead you to the profile information page. You can here manage your account information.

  • How can I delete my account ?

    You can delete your account anytime by going on your profile page and click on the “Edit Profile” link. On your profile editing page, you can click on the « Delete account ?» link at the bottom left of the page.

  • What is the map?

    The map on represents the marketplace. You can allow to locate your position to center the map around your position and to display other user’s posts around you. You can also just browse the map as you like. If you want to know more about ad, you can click on the red and white pin that appears on the map to see what the ad is about and click on it to display all the information.

  • How can I post an item ?

    It’s easy and free. You need first to create a Cartam profile. The more information you enter in, the more trust you build. Once logged in, on your account page or on the website main page, click on the « post an ad » button (usually top right of the screen) that will lead you in the post creation process. Step 1 Enter post title Select a category for the item you wish to post Step 2 Select a price type, which cryptocurrency do you want to be paid with ? Select the amount in fiat currency equivalent at which you want to sell your item Select the fiat currency corresponding to your local currency You can upload pictures of the item you wih to sell Ad Description: You can enter more information about your item in the Ad Description text box. We encourage you to enter as many information as possible Tags: You can ad tags that will help your product to be found in search results Youtube Video Link: you can add a demonstration of your product in video by entering the video link. Step 3 Your name: Enter your username, it will be displayed on the Ad information. Mobile Number (optional): you can ad a mobile number to be contacted on your phone about your ad Country: Select the country in which you want to post an ad. As is made for face to face transactions, we recommend that users enter the country in which they live. If your country is not on the list yet, be sure it will be added to the platform eventually State (optional): You can if you want look for the state or region in which you want to post your ad. Address: enter the address at which you want to sell your item. No need to enter your complete address, you can enter just a town or a street name. Once you are satisfied with your ad details, you can click on the “Submit” button to post your ad on the map!

  • What information to put in my post ?

    The more information about the ad you are creating, the better. We advise you to precisely detail everything you can about the item you want to sell as well as a relevant title for your post. Don’t hesitate to review the information about your offer and make sure it’s accurate, once you feel ready, you can post your ad ! Posts that don’t respect the terms & conditions of use will not be validated.

  • How to use the filter options ?

    Search option is available on the homepage below the map or by clicking on search on the upper navigation bar. You can freely filter what you want to see on the map using several metrics. The search bar, where you can enter directly what you are looking for Ad type: select if you want buying or selling ads. Ad price: sort results by price using the price line or enter directly the price you want Country location: choose the country/countries in which ads are featured in Category: select the categories of items in which you are interested in. There is 13 categories. Once you have entered the information that you wanted, click on the “search” button, will browse the marketplace to display what you have searched for.

  • How can I buy an item ?

    If you find an offer interesting on the map or by searching into the posted ads, you can view more details about it. You can then review the offer’s details and you can proceed into contacting the seller. Send a private message to the user that posted the ad you are interested in Ask more information and decide a place, time and date to meet Meet and proceed to the transaction using a personal blockchain wallet with the agreed item and price Users can rate each other and leave comments

  • How can I make a transaction (wallet to wallet)? is made for face to face transactions where one user pays the other with cryptocurrency for an item that the other user wish to sold. In order to send cryptocurrency, you need to have a functional blockchain wallet, own crypto and start the transaction process: The buyer and the seller (Sender of cryptocurrency and Receiver of cryptocurrency) must have a valid blockchain wallet Each user must active/unlock its wallet The seller (receiver) provide the public wallet address of the desired cryptocurrency The buyer (sender) enter the seller (receiver) public address (or QR code scan) The buyer (sender) enter the desired amount required for the established transaction The buyer (sender) valid the transaction and send the required amount pre-established The seller (receiver) receive the funds on its wallet The seller (receiver) confirm the transaction

  • Why and how do I report/block another user ?

    We do care about our community of users. If you notice inappropriate messages or behavior from another users, you can go in the message system and use the « block user » button. This way, the user you blocked won’t be able to contact you. You can also contact us on to let us know about any issues you may encounter.

  • How to use Cartam safely ?

    Cartam marketplace supply its user with search tool, make sure you make good use of those tools to really find ads interesting for you. Make sure to check seller/buying profile. Comments and ratings are here for you to have more information about another user. Give the community feedback when something good or wrong happen, this way you help the Cartam community and help us to improve the platform.