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Celo is an open-source EVM-compatible blockchain with an ecosystem focused on providing access to decentralized finance (DeFi) via smartphones.
The platform created by Celo functions as a global cryptocurrency payment infrastructure for cellphone users. It is designed to help anyone who wants to run a business in the financial sector to make payments worldwide by phone number. Thus, this blockchain ecosystem aims to make cryptocurrency popular among smartphone users.
The world first learned about Celo in 2017. And in 2019, the developers managed to attract $30 million in investments from a number of companies, including Andreessen Horowitz and Polychain. The project was under development until May 2020 when the the Celo network and its stablecoin CUSD were launched. Over the following years, Celo developed its key features, such as the ability to create smart contracts and decentralized applications (dApps).
The Celo Foundation, a non-profit organization, is responsible for developing and maintaining the network.
Celo blockchain uses the PoS (Proof of Stake) consensus algorithm. Celo's consensus protocol is based on an implementation called Istanbul or IBFT (Istanbul Byzantine Fault Tolerance). This consensus algorithm allows negotiating validity of transactions even if one-third of the nodes are malicious, faulty, or offline.
Network validators are chosen by CELO token holders who cast a vote with their voting coins. Due to the technicalities of the algorithm, accounts do not vote for each validator separately, but instead vote for groups of validators. The maximum number of active validators is currently 110. The active set of validators is determined by a share validation process and is updated approximately every other day.
Nodes must first stake 10,000 CELO tokens to run a validator, which means that anyone who owns CELO can help run the network. Validators can suffer punishment for their bad behavior. There are two major cases when validators are charged. The first one is persistent downtime — a validator which is absent from 8640 consecutive BLS signatures will be slashed 100 CELO, have future rewards suppressed, and (most importantly in this case) will be ejected from the current group. The second case is double signing — a validator which produced BLS signatures for two distinct blocks at the same height and in the same consensus round but with different hashes will be slashed 9,000 CELO, have future rewards suppressed, and will be ejected from the current group.
The Celo network consists of a three-tier node structure: validators, full nodes, and clients. Therefore, not only validators can earn CELO, but also full-node holders who transfer data from the client to the validator for a fee paid by the transaction initiator.
Validators are responsible for transaction processing and blockchain formation, as well as creation of new tokens. They store a full copy of the blockchain. The minimum requirement to become a validator is 10,000 CELO.
Full nodes act as a bridge between validators and mobile wallets; they receive requests from clients and redirect transactions to validators. They store a partial copy of the blockchain.
Clients, or so-called light clients, are applications on users’ smartphones that do not perform mining or validate transactions. An example of such applications is a mobile wallet.
Celo's mobile-optimized blockchain automatically charges transaction fees and allows users to pay Gas fees using any ERC-20 token.
The flagship app built on Celo and the first dApp in the network ecosystem is the Celo Wallet, called Valora, developed directly by the blockchain team. This application allows a full disposal of CUSD and token transfers and payments for goods and services with stablecoins. The wallet is a smartphone application and is available in app stores for the most common smartphone operating systems.
While the Celo app is the platform's preferred way to send stablecoins, users can also send cUSD via WhatsApp. However, the recipient must still download and install the Celo wallet to receive cUSD. While Celo fees fluctuate depending on the demand for the network's services, currently most transfer fees are below $0.001.
CELO tokens can be stored on all multicurrency wallets compatible with ERC-20 format tokens (Metamask, TrustWallet, etc.).
By getting rid of cumbersome public keys and replacing them with cell phone numbers that most users are used to, the Celo team has greatly simplified user interaction. The cell phone number is linked to the wallet address, and the cryptographic hash of the phone number is stored on the blockchain.
After installing the wallet and connecting the mobile number, the user receives an SMS with a code. After the code is entered in the app, the system begins synchronizing the wallet with the mobile device. At the same time, phone numbers can be added or deleted from the wallet address list at any time.
An important feature of the Celo blockchain is the decentralized EigenTrust algorithm. This algorithm measures a user's online reputation in the same way that a normal credit rating measures financial reputation. EigenTrust was developed for Google in 2002 by Sep Kamvar, co-founder of Celo, and was previously used as a key component of the Google PageRank algorithm.
Celo is a proof-of-stake blockchain. On Celo, users can use their CELO tokens to vote/stake on a group of validators. This brings rewards to the voters and also helps protect the Celo network. Staking CELO tokens can be done through most current Celo wallets. To vote for a group of validators, users need to lock their CELO into a Locked Gold contract. If the voted validators group works well, the voter earns a certain amount of CELO every day. Otherwise, if the validators suffer a slashing penalty, the voter’s rewards are halved.
Voters can revoke their votes at any time. Thus, they can avoid a decrease in their earnings when the validators are performing poorly and vote for another group, which has zero or low slashing time in the past and low slashing value.
The economic model of Celo is based on three tokens.
CELO is a native coin with a fixed supply of 1,000,000,000 tokens and a floating rate. The token is used to pay fees, vote on community proposals, and mint stablecoins. During the launch of the network in May 2020, the developers pre-mined 60% (600 million) of the total supply. The remaining 40% must be mined by validators.
CELO tokens have the following utilities: participating in management decisions on the platform; maintaining stable currencies (initially, Celo dollars) on the platform and overvaluing reserves that maintain price stability; incentivising validators to secure and launch the network.
cUSD/cEUR are stablecoins pegged to the dollar and euro, respectively, with instant liquidity provided by Celo's internal dollar reserves.
Users can freely convert CELO into cUSD/cEUR and back, as well as transfer these tokens to any other user. In order to mint a stablecoin, the corresponding amount of CELO tokens must be frozen on the platform, which means that the CELO exchange rate is directly related to the demand for cUSD/cEUR stablecoins.
The stabilization algorithm ensures a stable coin exchange rate by providing a whole basket of cryptocurrencies and other assets, as well as oracles that provide market value data.
Currently, the team consists of 106 people. All team members have social media profiles and are completely open to the community. The team members come from many disciplines, including software development, blockchain technology, marketing, business, finance, and more.
Celo's three co-founders are Sep Kamvar, Rene Rainsberg, and Marek Olszewski.
Rene Reinsberg is responsible for the business. Most recently, Rene was an executive director of General Catalyst Partners. Previously, he was GoDaddy's vice president of emerging products. He co-founded Locu and served as CEO until Locu was acquired by GoDaddy in August 2013. Rene began his career in global capital markets at Morgan Stanley and has also worked at McKinsey, World Bank, and TechnoServe. He holds a finance degree from WHU, Germany and an MBA from MIT Sloan. Rene is an active consultant and investor in more than 50 companies.
Sep Kamvar is the inventor of the EigenTrust digital reputation system, which was once used by Google as part of its PageRank algorithm. Before joining Celo, he was a partner at Wildflower School and an assistant professor at MIT. Previously, he was a consulting professor at Stanford University and also worked as a lead personalization engineer at Google.
Marek Olszewski is an ambitious computer engineer with a PhD in computer science from MIT. He also worked at Microsoft Research, Google, and Sun Labs before founding the machine intelligence startup Locu. After the company was acquired by GoDaddy, he served as vice president of development at GoDaddy until he moved to Celo.
Celo was audited by OpenZeppelin in February 2021 and NCCgroup in April 2020.
There are also contract audit reports by Certora, security audit reports by Trailofbits and Teserakt, and economic audit reports by Prysm Group and Gauntlet, however, the report files were not provided by the Celo team.
Since the mainnet launch in 2020, Celo's network now supports more than 1,000 projects from builders, developers, and artists who create new apps and digital currencies. Celo partners include projects such as Blockchain.com, The Graph, Mysten Labs, and others.
At the moment, the Celo team is actively working on increased blockchain speed and greater decentralization. This will be achieved by growing the number of full nodes and moving to a batch offering of multi-signature validators, which will increase the size of the validator set. Also, Celo is going to integrate the Move virtual machine and implement ZK-rollups.
The Celo community has a strong background in zk-SNARKs as seen by the work on Plumo and Poof. That is why the team plans to continue to invest in zk-SNARK technology, from such areas as bridges, rollups, to compliance protocols.
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Last updated: Aug 22, 2023
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