Asset Anything that has value to a stakeholder. Block Data structure comprising a block header and block data. Blockchain Specific type of DLT. Database which is: distributed append-only organized in sequential blocks: chained together using cryptographic links whose content is made by consensus Blockchains are designed to be tamper resistant and to create final, definitive and immutable ledger records. Block data Data structure comprising zero or more transaction records or refe...

I discovered cryptocurrencies in 2017. First it was not even Bitcoin, but Bitcoin Cash. Then Ethereum and its merry flock of tokens. Then I caught the virus. The virus spread. I eventually went beyond cryptocurrencies and got interested by the technology itself: Blockchain. Cryptocurrencies remain my favorite use case. Therefore I deliberately expose myself to a significant amount of information and news related to cryptocurrencies. Decentralization has always been one of the most (if not THE) d...

Sapiens can cooperate in extremely flexible ways with countless numbers of strangers. That’s why Sapiens rule the world, whereas ants eat our leftovers and chimps are locked up in zoos and research laboratories." - Y.N.Harari, Sapiens: A brief History of Humankind. Humans rule the world because they can collaborate flexibly at scale. One way they found to cooperate is forming networks: A network of people or institutions is a large number of them that have a connection with each other and w...

The Ethernaut is a Web3/Solidity based wargame inspired from overthewire.org, played in the Ethereum Virtual Machine. Each level is a smart contract that needs to be 'hacked'. goto: Alien Codex Shop Level 19 - Denial Target This is a simple wallet that drips funds over time. You can withdraw the funds slowly by becoming a withdrawing partner. If you can deny the owner from withdrawing funds when they call withdraw() (whilst the contract still has funds) you will win this level. Contract...

The Ethernaut is a Web3/Solidity based wargame inspired from overthewire.org, played in the Ethereum Virtual Machine. Each level is a smart contract that needs to be 'hacked'. goto: Recovery MagicNumber Level 16 - Preservation Target A contract creator has built a very simple token factory contract. Anyone can create new tokens with ease. After deploying the first token contract, the creator sent 0.5 ether to obtain more tokens. They have since lost the contract address. This level will b...

The Ethernaut is a Web3/Solidity based wargame inspired from overthewire.org, played in the Ethereum Virtual Machine. Each level is a smart contract that needs to be 'hacked'. goto: Gatekeeper Two Naught Coin Level 13 - Gatekeeper One Target: make it past the gatekeeper. Contract pragma solidity ^0.5.0; import 'openzeppelin-solidity/contracts/math/SafeMath.sol'; contract GatekeeperOne { using SafeMath for uint256; address public entrant; modifier gateOne() { require(msg.sende...

The Ethernaut is a Web3/Solidity based wargame inspired from overthewire.org, played in the Ethereum Virtual Machine. Each level is a smart contract that needs to be 'hacked'. goto: Privacy Elevator Level 10 - Reentrancy Target: steal all funds from the contract. Contract pragma solidity ^0.5.0; import 'openzeppelin-solidity/contracts/math/SafeMath.sol'; contract Reentrance { using SafeMath for uint256; mapping(address => uint) public balances; function donate(address _to) pub...

The Ethernaut is a Web3/Solidity based wargame inspired from overthewire.org, played in the Ethereum Virtual Machine. Each level is a smart contract that needs to be 'hacked'. goto: Vault King Level 7 - Force Target: make the balance of the contract greater than zero. Contract pragma solidity ^0.5.0; contract Force {/* MEOW ? /\_/\ / ____/ o o \ /~____ =ø= / (______)__m_m) */} Solidity Concept: selfdestruct 3 methods exist to receive Ethers: Me...

The Ethernaut is a Web3/Solidity based wargame inspired from overthewire.org, played in the Ethereum Virtual Machine. Each level is a smart contract that needs to be 'hacked'. go to: Token Delegation Level 4 - Telephone Target: claim ownership of the contract. Contract pragma solidity ^0.5.0; contract Telephone { address public owner; constructor() public { owner = msg.sender; } function changeOwner(address _owner) public { if (tx.origin != msg.sender) { owner = _...

The Ethernaut is a Web3/Solidity based wargame inspired from overthewire.org, played in the Ethereum Virtual Machine. Each level is a smart contract that needs to be 'hacked'. goto: Fallout Coin Flip Level 1 - Fallback Target: claim ownership of the contract & reduce its balance to 0. Contract pragma solidity ^0.5.0; import 'openzeppelin-solidity/contracts/math/SafeMath.sol'; contract Fallback { using SafeMath for uint256; mapping(address => uint) public contributions; addr...

Introduction In the most famous blockchains protocols (e.g Bitcoin or Ethereum) addresses are partly obfuscated by the fact that addresses are pseudo anonymous: they aren't directly tied with an identity. However chain analysis can succeed in discovering the identity associated with a given address. We've seen that for instance CoinJoin offers a solution to break the link between sender and receiver. CoinJoin still provides limited privacy because it doesn't obfuscate the transaction amounts. L...

Introduction Backup your private key. Never share your private key. Not your keys, not your bitcoins. Send to: Paste public 0x... address Although, the use of jargon has been reduced to improve UX and onboard more users, the terms "private key, public key, public address, signatures" are still common. Users will also encounter mainstream definitions of blockchain and cryptocurrencies mixing the terms "database, cryptography, security, confidentiality". How does it all fit together? What is th...

Introduction “Where does a wise man hide a leaf? In the forest. But what does he do if there is no forest? He grows a forest to hide it in.” ― G K Chesterton, The Innocence of Father Brown "Mixing" technologies rely on obfuscation to hide sensitive information (identity, transaction data) and ultimately ensure privacy and anonymity. Obfuscation commonly takes various forms: adding noise to cover conversation, blend in a crowd, create copies or decoys, natural camouflage... In the context of blo...

"When you change the medium, the message changes" Said Bitcoin Evangelist Andreas M. Antonopoulos in this talk. The term "streaming" was coined when Internet superseded physical containers (CDs & VHS) as main 'container' for audiovisual content. Product/Industry Old medium Today Music CD, Vynils, tapes Streaming Video VHS, tapes Streaming News Newspapers, print outs, books, radio Blog posts, tweet, podcasts Behaviours regarding the consumption of music and video were condition...

Privacy matters It makes possible for us to develop as free-thinking, independent individuals. One common nonsense argument against the importance of privacy is: I have nothing to hide, so why should I care about my privacy? Following this logic we go on declaring: I having nothing to say, so why should I care about my freedom of speech? There is nowhere I want to move/travel to, so why should I care about my freedom of movement? I don't believe in any gods, so why should I care about freedom ...

Scott Adams Talent Stack Most of the time, excellence and greatness are understood as specific: "the fatest...", "the best x-player", "the best in x discipline...", "the expert in field x...". So the obvious way to become valuable is specialization. This requires a lot a discipline, time, patience and personal drive. Scott Adams Talent Stack offers a different path. It says that even if your skill level is mediocre, if the mix of skills is right, you can become unique and valuable too. This pat...

I actually introduced in my previous post what zero knowledge proofs are just for the sake of introducing this application I am very excited about: CODA. CODA uses zk-SNARKS to build a tiny, constant-size blockchain. So tiny that it could run natively in browsers! If you're still reading this after reading the very title of this post, I think I can also assume that you are familiar with the concepts of blockchain and zero knowledge proofs. CODA is a new cryptocurrency protocol built on a "succ...

In most of the situtations where you (Prover) make a statement and have to prove its authenticity to someone (Verifier), you'll actually have to disclose the actual value of the statement's argument. Examples Situation Statement Argument What is disclosed as a practical proof Voting, Driving, Buying alcohol... I am over 18 yo Age ID card: actual age, birthdate, name Execute a bank transfer or card transaction I have enough funds on my account Account balance Actual account value Mathem...

I don't believe that private blockchains will become global. They will be confined to national governmental use or to industry specific consortiums. I'll try to demonstrate my position by examining the architecture choice that different users may take through the lens of the following human motivations. Motivations Acquire (greed) – Desire to collect physical objects as well as immaterial ones like power, status, and influence Defend (fear) – Desire to protect ourselves and our property Bond (...

Common sense tells us that scarce things are valuable or costly. Scarce things such as precious metals or antiques are especially costly because they are hard to create for anyone. Nick Szabo calls this property of being costly to forge "unforgeable costliness". Unforgeable costliness provides value independently from 3rd parties. Monetary systems are based on objects that are naturally (precious metals) or artificially (fiat and accouting) unforgeably costly. However we can't really pay with me...

Upon reading the "Fate of Food" article in the Imagine 2030 report from Deutsche Bank Research, I starting reconsidering my opinions on the food industry current problems and potential solutions. I tend to feel bad when I indulge myself ordering a meal and I have always refused to make use of a meal-kit service such as HelloFresh. Indeed,besides food quality and costs considerations, isn't it non sense from an ecology, energy or sustainability point of view? More packaging, more transport costs,...

For a technical definition, read here. A non technical definition is: "a technology that enables digital exchanges of value between entities that don't trust each other without intermediary". Why does it matter? Internet: information network If you are reading this post, I can safely bet you know you what Internet is. So you should be able to wrap your head around the idea of what a network is: Internet being something often referred as THE NETWORK. One can be 'part of', 'on a', 'connected to'...

Asset Anything that has value to a stakeholder. Block Data structure comprising a block header and block data. Blockchain Specific type of DLT. Database which is: distributed append-only organized in sequential blocks: chained together using cryptographic links whose content is made by consensus Blockchains are designed to be tamper resistant and to create final, definitive and immutable ledger records. Block data Data structure comprising zero or more transaction records or refe...

This TED talk from Aaswath Raman really puzzled me and made so optimistic and hopeful for our planet's future. Issue The alarming starting point is the vicious circle of cooling we are currently stucked in: We cool: To live and sleep comfortably in places where the heat can become unbearable. To keep our food longer To operate data centers The warmer it gets, the more we need to cool. Back to --> 1: vicious feedback loop. Cooling energy counts to 17% of global electrical use and 8% o...

Kickstarter helps artists, musicians, filmmakers, designers, and other creators find the resources and support they need to make their ideas a reality. Potential future customers, 'backers', can contribute to a project to finance the development of a product. Sounds awesome. However, a fundamental problem for crowdfunding is how asymmetrical the risks faced by backers and founders are. After having invested, backers don't get a say on how their money will actually be spent. Worse: which guarante...

The Bayern LB is a german state-owned bank. Their research unit recently published a report titled Megatrend Digitalisierung. Highlights "an asset with a high stock to flow ratio (like gold) is said to be hard" "Historically, assets with the highest stock to flow ratio have always been always used as money, as it enabled the best value transfer over time" "Bitcoin was engineered to be harder than gold". eventually (better late than never)...they notice the strong correlation of Bitcoin's st...

WePower/Elering Nationwide Energy Experiment Hinsights from WePower website: WePower’s mission is to enable everyone to make a change towards a sustainable energy future through their energy purchasing decisions. WePower essentially tackles the limitations of the current instruments that exist in the market, especially Power Purchase Agreements (PPAs), which are too complex and expensive for corporate energy buyers. That's why WePower has built a next-generation renewable ...

The motivation to write these lines came from seeing both bad/good visualizations, both at work or in the medias. So here are some principles that should help build better visualizations or detect flaws in poorly designed visualizations. I'll start assuming you have some data (symbols, signs, bytes, characters….) that you interpreted to get some information out of it. You now want to communicate it and present it to others. One effective communication is often visual communication. Back to data,...

Block ads and access your data everywhere: self-hosted DNS+VPN+FTP+CLOUD server I used to rely on cloud services offered by 'powerful, centralized, privately-owned companies' to store and share data between my personal devices. Not happy with their valuing of privacy, I decided to host myself a server. It should fulfill the following requirements: [ ] 'network firewall' or 'DNS sinkhole' to block ads and trackers. [ ] file server (ftp) [ ] cloud server (http) [ ] store data on a separate ...