More on Web3 & Crypto
mbvissers.eth
3 years ago
Why does every smart contract seem to implement ERC165?
ERC165 (or EIP-165) is a standard utilized by various open-source smart contracts like Open Zeppelin or Aavegotchi.
What's it? You must implement? Why do we need it? I'll describe the standard and answer any queries.
What is ERC165
ERC165 detects and publishes smart contract interfaces. Meaning? It standardizes how interfaces are recognized, how to detect if they implement ERC165, and how a contract publishes the interfaces it implements. How does it work?
Why use ERC165? Sometimes it's useful to know which interfaces a contract implements, and which version.
Identifying interfaces
An interface function's selector. This verifies an ABI function. XORing all function selectors defines an interface in this standard. The following code demonstrates.
// SPDX-License-Identifier: UNLICENCED
pragma solidity >=0.8.0 <0.9.0;
interface Solidity101 {
function hello() external pure;
function world(int) external pure;
}
contract Selector {
function calculateSelector() public pure returns (bytes4) {
Solidity101 i;
return i.hello.selector ^ i.world.selector;
// Returns 0xc6be8b58
}
function getHelloSelector() public pure returns (bytes4) {
Solidity101 i;
return i.hello.selector;
// Returns 0x19ff1d21
}
function getWorldSelector() public pure returns (bytes4) {
Solidity101 i;
return i.world.selector;
// Returns 0xdf419679
}
}This code isn't necessary to understand function selectors and how an interface's selector can be determined from the functions it implements.
Run that sample in Remix to see how interface function modifications affect contract function output.
Contracts publish their implemented interfaces.
We can identify interfaces. Now we must disclose the interfaces we're implementing. First, import IERC165 like so.
pragma solidity ^0.4.20;
interface ERC165 {
/// @notice Query if a contract implements an interface
/// @param interfaceID The interface identifier, as specified in ERC-165
/// @dev Interface identification is specified in ERC-165.
/// @return `true` if the contract implements `interfaceID` and
/// `interfaceID` is not 0xffffffff, `false` otherwise
function supportsInterface(bytes4 interfaceID) external view returns (bool);
}We still need to build this interface in our smart contract. ERC721 from OpenZeppelin is a good example.
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC721/ERC721.sol)
pragma solidity ^0.8.0;
import "./IERC721.sol";
import "./extensions/IERC721Metadata.sol";
import "../../utils/introspection/ERC165.sol";
// ...
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
// ...
function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
return
interfaceId == type(IERC721).interfaceId ||
interfaceId == type(IERC721Metadata).interfaceId ||
super.supportsInterface(interfaceId);
}
// ...
}I deleted unnecessary code. The smart contract imports ERC165, IERC721 and IERC721Metadata. The is keyword at smart contract declaration implements all three.
Kind (interface).
Note that type(interface).interfaceId returns the same as the interface selector.
We override supportsInterface in the smart contract to return a boolean that checks if interfaceId is the same as one of the implemented contracts.
Super.supportsInterface() calls ERC165 code. Checks if interfaceId is IERC165.
function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
return interfaceId == type(IERC165).interfaceId;
}So, if we run supportsInterface with an interfaceId, our contract function returns true if it's implemented and false otherwise. True for IERC721, IERC721Metadata, andIERC165.
Conclusion
I hope this post has helped you understand and use ERC165 and why it's employed.
Have a great day, thanks for reading!
Vitalik
4 years ago
An approximate introduction to how zk-SNARKs are possible (part 2)
If tasked with the problem of coming up with a zk-SNARK protocol, many people would make their way to this point and then get stuck and give up. How can a verifier possibly check every single piece of the computation, without looking at each piece of the computation individually? But it turns out that there is a clever solution.
Polynomials
Polynomials are a special class of algebraic expressions of the form:
- x+5
- x^4
- x^3+3x^2+3x+1
- 628x^{271}+318x^{270}+530x^{269}+…+69x+381
i.e. they are a sum of any (finite!) number of terms of the form cx^k
There are many things that are fascinating about polynomials. But here we are going to zoom in on a particular one: polynomials are a single mathematical object that can contain an unbounded amount of information (think of them as a list of integers and this is obvious). The fourth example above contained 816 digits of tau, and one can easily imagine a polynomial that contains far more.
Furthermore, a single equation between polynomials can represent an unbounded number of equations between numbers. For example, consider the equation A(x)+ B(x) = C(x). If this equation is true, then it's also true that:
- A(0)+B(0)=C(0)
- A(1)+B(1)=C(1)
- A(2)+B(2)=C(2)
- A(3)+B(3)=C(3)
And so on for every possible coordinate. You can even construct polynomials to deliberately represent sets of numbers so you can check many equations all at once. For example, suppose that you wanted to check:
- 12+1=13
- 10+8=18
- 15+8=23
- 15+13=28
You can use a procedure called Lagrange interpolation to construct polynomials A(x) that give (12,10,15,15) as outputs at some specific set of coordinates (eg. (0,1,2,3)), B(x) the outputs (1,8,8,13) on thos same coordinates, and so forth. In fact, here are the polynomials:
- A(x)=-2x^3+\frac{19}{2}x^2-\frac{19}{2}x+12
- B(x)=2x^3-\frac{19}{2}x^2+\frac{29}{2}x+1
- C(x)=5x+13
Checking the equation A(x)+B(x)=C(x) with these polynomials checks all four above equations at the same time.
Comparing a polynomial to itself
You can even check relationships between a large number of adjacent evaluations of the same polynomial using a simple polynomial equation. This is slightly more advanced. Suppose that you want to check that, for a given polynomial F, F(x+2)=F(x)+F(x+1) with the integer range {0,1…89} (so if you also check F(0)=F(1)=1, then F(100) would be the 100th Fibonacci number)
As polynomials, F(x+2)-F(x+1)-F(x) would not be exactly zero, as it could give arbitrary answers outside the range x={0,1…98}. But we can do something clever. In general, there is a rule that if a polynomial P is zero across some set S=\{x_1,x_2…x_n\} then it can be expressed as P(x)=Z(x)*H(x), where Z(x)=(x-x_1)*(x-x_2)*…*(x-x_n) and H(x) is also a polynomial. In other words, any polynomial that equals zero across some set is a (polynomial) multiple of the simplest (lowest-degree) polynomial that equals zero across that same set.
Why is this the case? It is a nice corollary of polynomial long division: the factor theorem. We know that, when dividing P(x) by Z(x), we will get a quotient Q(x) and a remainder R(x) is strictly less than that of Z(x). Since we know that P is zero on all of S, it means that R has to be zero on all of S as well. So we can simply compute R(x) via polynomial interpolation, since it's a polynomial of degree at most n-1 and we know n values (the zeros at S). Interpolating a polynomial with all zeroes gives the zero polynomial, thus R(x)=0 and H(x)=Q(x).
Going back to our example, if we have a polynomial F that encodes Fibonacci numbers (so F(x+2)=F(x)+F(x+1) across x=\{0,1…98\}), then I can convince you that F actually satisfies this condition by proving that the polynomial P(x)=F(x+2)-F(x+1)-F(x) is zero over that range, by giving you the quotient:
H(x)=\frac{F(x+2)-F(x+1)-F(x)}{Z(x)}
Where Z(x) = (x-0)*(x-1)*…*(x-98).
You can calculate Z(x) yourself (ideally you would have it precomputed), check the equation, and if the check passes then F(x) satisfies the condition!
Now, step back and notice what we did here. We converted a 100-step-long computation into a single equation with polynomials. Of course, proving the N'th Fibonacci number is not an especially useful task, especially since Fibonacci numbers have a closed form. But you can use exactly the same basic technique, just with some extra polynomials and some more complicated equations, to encode arbitrary computations with an arbitrarily large number of steps.
see part 3
CoinTelegraph
4 years ago
2 NFT-based blockchain games that could soar in 2022
NFTs look ready to rule 2022, and the recent pivot toward NFT utility in P2E gaming could make blockchain gaming this year’s sector darling.
After the popularity of decentralized finance (DeFi) came the rise of nonfungible tokens (NFTs), and to the surprise of many, NFTs took the spotlight and now remain front and center with the highest volume in sales occurring at the start of January 2022.
While 2021 became the year of NFTs, GameFi applications did surpass DeFi in terms of user popularity. According to data from DappRadar, Bloomberg gathered:
Nearly 50% of active cryptocurrency wallets connected to decentralized applications in November were for playing games. The percentage of wallets linked to decentralized finance, or DeFi, dapps fell to 45% during the same period, after months of being the leading dapp use case.
Blockchain play-to-earn (P2E) game Axie infinity skyrocketed and kicked off a gaming craze that is expected to continue all throughout 2022. Crypto pundits and gaming advocates have high expectations for P2E blockchain-based games and there’s bound to be a few sleeping giants that will dominate the sector.
Let’s take a look at five blockchain games that could make waves in 2022.
DeFi Kingdoms
The inspiration for DeFi Kingdoms came from simple beginnings — a passion for investing that lured the developers to blockchain technology. DeFi Kingdoms was born as a visualization of liquidity pool investing where in-game ‘gardens’ represent literal and figurative token pairings and liquidity pool mining.
As shown in the game, investors have a portion of their LP share within a plot filled with blooming plants. By attaching the concept of growth to DeFi protocols within a play-and-earn model, DeFi Kingdoms puts a twist on “playing” a game.
Built on the Harmony Network, DeFi Kingdoms became the first project on the network to ever top the DappRadar charts. This could be attributed to an influx of individuals interested in both DeFi and blockchain games or it could be attributed to its recent in-game utility token JEWEL surging.
JEWEL is a utility token that allows users to purchase NFTs in-game buffs to increase a base-level stat. It is also used for liquidity mining to grant users the opportunity to make more JEWEL through staking.
JEWEL is also a governance token that gives holders a vote in the growth and evolution of the project. In the past four months, the token price surged from $1.23 to an all-time high of $22.52. At the time of writing, JEWEL is down by nearly 16%, trading at $19.51.
Surging approximately 1,487% from its humble start of $1.23 four months ago in September, JEWEL token price has increased roughly 165% this last month alone, according to data from CoinGecko.
Guild of Guardians
Guild of Guardians is one of the more anticipated blockchain games in 2022 and it is built on ImmutableX, the first layer-two solution built on Ethereum that focuses on NFTs. Aiming to provide more access, it will operate as a free-to-play mobile role-playing game, modeling the P2E mechanics.
Similar to blockchain games like Axie Infinity, Guild of Guardians in-game assets can be exchanged. The project seems to be of interest to many gamers and investors with its NFT founder sale and token launch generating nearly $10 million in volume.
Launching its in-game token in October of 2021, the Guild of Guardians (GOG) tokens are ERC-20 tokens known as ‘gems’ inside the game. Gems are what power key features in the game such as minting in-game NFTs and interacting with the marketplace, and are available to earn while playing.
For the last month, the Guild of Guardians token has performed rather steadily after spiking to its all-time high of $2.81 after its launch. Despite the token being down over 50% from its all-time high, at the time of writing, some members of the community are looking forward to the possibility of staking and liquidity pools, which are features that tend to help stabilize token prices.
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Gareth Willey
3 years ago
I've had these five apps on my phone for a long time.
TOP APPS
Who survives spring cleaning?
Relax. Notion is off-limits. This topic is popular.
(I wrote about it 2 years ago, before everyone else did.) So).
These apps are probably new to you. I hope you find a new phone app after reading this.
Outdooractive
ViewRanger is Google Maps for outdoor enthusiasts.
This app has been so important to me as a freedom-loving long-distance walker and hiker.
This app shows nearby trails and right-of-ways on top of an Open Street Map.
Helpful detail and data. Any route's distance,
You can download and follow tons of routes planned by app users.
This has helped me find new routes and places a fellow explorer has tried.
Free with non-intrusive ads. Years passed before I subscribed. Pro costs £2.23/month.
This app is for outdoor lovers.
Google Files
New phones come with bloatware. These rushed apps are frustrating.
We must replace these apps. 2017 was Google's year.
Files is a file manager. It's quick, innovative, and clean. They've given people what they want.
It's easy to organize files, clear space, and clear cache.
I recommend Gallery by Google as a gallery app alternative. It's quick and easy.
Trainline
App for trains, buses, and coaches.
I've used this app for years. It did the basics well when I first used it.
Since then, it's improved. It's constantly adding features to make traveling easier and less stressful.
Split-ticketing helps me save hundreds a year on train fares. This app is only available in the UK and Europe.
This service doesn't link to a third-party site. Their app handles everything.
Not all train and coach companies use this app. All the big names are there, though.
Here's more on the app.
Battlefield: Mobile
Play Store has 478,000 games. Few can turn my phone into a console.
Call of Duty Mobile and Asphalt 8/9 are examples.
Asphalt's loot boxes and ads make it unplayable. Call of Duty opens with a few ads. Close them to play without hassle.
This game uses all your phone's features to provide a high-quality, seamless experience. If my internet connection is good, I never experience lag or glitches.
The gameplay is energizing and intense, just like on consoles. Sometimes I'm too involved. I've thrown my phone in anger. I'm totally absorbed.
Customizability is my favorite. Since phones have limited screen space, we should only have the buttons we need, placed conveniently.
Size, opacity, and position are modifiable. Adjust audio, graphics, and textures. It's customizable.
This game has been on my phone for three years. It began well and has gotten better. When I think the creators can't do more, they do.
If you play, read my tips for winning a Battle Royale.
Lightroom
As a photographer, I believe your best camera is on you. The phone.
2017 was a big year for this app. I've tried many photo-editing apps since then. This always wins.
The app is dull. I've never seen better photo editing on a phone.
Adjusting settings and sliders doesn't damage or compress photos. It's detailed.
This is important for phone photos, which are lower quality than professional ones.
Some tools are behind a £4.49/month paywall. Adobe must charge a subscription fee instead of selling licenses. (I'm still bitter about Creative Cloud's price)
Snapseed is my pick. Lightroom is where I do basic editing before moving to Snapseed. Snapseed review:
These apps are great. They cover basic and complex editing needs while traveling.
Final Reflections
I hope you downloaded one of these. Share your favorite apps. These apps are scarce.
Jano le Roux
3 years ago
The Real Reason Adobe Just Paid $20 billion for Figma
Sketch or Figma?
Designers are pissed.
The beast ate the beauty.
Figma deserves $20B.
Do designers deserve Adobe?
Adobe devours new creative tools and spits them out with a slimy Adobe aftertaste.
Frame.io — $1.3B
Magento — $1.7B
Macromedia — $3.6B
Nothing compares to the risky $20B acquisition.
If they can't be beaten, buy them.
And then make them boring.
Adobe's everywhere.
Like that friend who dabbles in everything creatively, there's not enough time to master one thing.
Figma was Adobe's thigh-mounted battle axe.
a UX design instrument with a sizable free tier.
a UX design tool with a simple and quick user interface.
a tool for fluid collaboration in user experience design.
a web-based UX design tool that functions well.
a UX design tool with a singular goal of perfection.
UX design software that replaced Adobe XD.
Adobe XD could do many of Figma's things, but it didn't focus on the details. This is a major issue when working with detail-oriented professionals.
UX designers.
Design enthusiasts first used Figma. More professionals used it. Institutions taught it. Finally, major brands adopted Figma.
Adobe hated that.
Adobe dispatched a team of lawyers to resolve the Figma issue, as big companies do. Figma didn’t bite for months.
Oh no.
Figma resisted.
Figma helped designers leave Adobe. Figma couldn't replace Photoshop, but most designers used it to remove backgrounds.
Online background removal tools improved.
The Figma problem grew into a thorn, a knife, and a battle ax in Adobe's soft inner thigh.
Figma appeared to be going public. Adobe couldn’t allow that. It bought Figma for $20B during the IPO drought.
Adobe has a new issue—investors are upset.
The actual cause of investors' ire toward Adobe
Spoiler: The math just doesn’t add up.
According to Adobe's press release, Figma's annual recurring revenue (ARR) is $400M and growing rapidly.
The $20B valuation requires a 50X revenue multiple, which is unheard of.
Venture capitalists typically use:
10% to 29% growth per year: ARR multiplied by 1 to 5
30% to 99% growth per year: ARR multiplied by 6 to 10
100% to 400% growth per year: ARR multiplied by 10 to 20
Showing an investor a 50x multiple is like telling friends you saw a UFO. They'll think you're crazy.
Adobe's stock fell immediately after the acquisition because it didn't make sense to a number-cruncher.
Designers started a Tweet storm in the digital town hall where VCs and designers often meet.
Adobe acquired Workfront for $1.5 billion at the end of 2020. This purchase made sense for investors.
Many investors missed the fact that Adobe is acquiring Figma not only for its ARR but also for its brilliant collaboration tech.
Adobe could use Figmas web app technology to make more products web-based to compete with Canva.
Figma's high-profile clients could switch to Adobe's enterprise software.
However, questions arise:
Will Adobe make Figma boring?
Will Adobe tone down Figma to boost XD?
Would you ditch Adobe and Figma for Sketch?
Niharikaa Kaur Sodhi
3 years ago
The Only Paid Resources I Turn to as a Solopreneur
4 Pricey Tools That Are Valuable
I pay based on ROI (return on investment).
If a $20/month tool or $500 online course doubles my return, I'm in.
Investing helps me build wealth.
Canva Pro
I initially refused to pay.
My course content needed updating a few months ago. My Google Docs text looked cleaner and more professional in Canva.
I've used it to:
product cover pages
eBook covers
Product page infographics
See my Google Sheets vs. Canva product page graph.
Google Sheets vs Canva
Yesterday, I used it to make a LinkedIn video thumbnail. It took less than 5 minutes and improved my video.
In 30 hours, the video had 39,000 views.
Here's more.
HypeFury
Hypefury rocks!
It builds my brand as I sleep. What else?
Because I'm traveling this weekend, I planned tweets for 10 days. It took me 80 minutes.
So while I travel or am absent, my content mill keeps producing.
Also I like:
I can reach hundreds of people thanks to auto-DMs. I utilize it to advertise freebies; for instance, leave an emoji remark to receive my checklist. And they automatically receive a message in their DM.
Scheduled Retweets: By appearing in a different time zone, they give my tweet a second chance.
It helps me save time and expand my following, so that's my favorite part.
It’s also super neat:
Zoom Pro
My course involves weekly and monthly calls for alumni.
Google Meet isn't great for group calls. The interface isn't great.
Zoom Pro is expensive, and the monthly payments suck, but it's necessary.
It gives my students a smooth experience.
Previously, we'd do 40-minute meetings and then reconvene.
Zoom's free edition limits group calls to 40 minutes.
This wouldn't be a good online course if I paid hundreds of dollars.
So I felt obligated to help.
YouTube Premium
My laptop has an ad blocker.
I bought an iPad recently.
When you're self-employed and work from home, the line between the two blurs. My bed is only 5 steps away!
When I read or watched videos on my laptop, I'd slide into work mode. Only option was to view on phone, which is awkward.
YouTube premium handles it. No more advertisements and I can listen on the move.
3 Expensive Tools That Aren't Valuable
Marketing strategies are sometimes aimed to make you feel you need 38474 cool features when you don’t.
Certain tools are useless.
I found it useless.
Depending on your needs. As a writer and creator, I get no return.
They could for other jobs.
Shield Analytics
It tracks LinkedIn stats, like:
follower growth
trend chart for impressions
Engagement, views, and comment stats for posts
and much more.
Middle-tier creator costs $12/month.
I got a 25% off coupon but canceled my free trial before writing this. It's not worth the discount.
Why?
LinkedIn provides free analytics. See:
Not thorough and won't show top posts.
I don't need to see my top posts because I love experimenting with writing.
Slack Premium
Slack was my classroom. Slack provided me a premium trial during the prior cohort.
I skipped it.
Sure, voice notes are better than a big paragraph. I didn't require pro features.
Marketing methods sometimes make you think you need 38474 amazing features. Don’t fall for it.
Calendly Pro
This may be worth it if you get many calls.
I avoid calls. During my 9-5, I had too many pointless calls.
I don't need:
ability to schedule calls for 15, 30, or 60 minutes: I just distribute each link separately.
I have a Gumroad consultation page with a payment option.
follow-up emails: I hardly ever make calls, so
I just use one calendar, therefore I link to various calendars.
I'll admit, the integrations are cool. Not for me.
If you're a coach or consultant, the features may be helpful. Or book meetings.
Conclusion
Investing is spending to make money.
Use my technique — put money in tools that help you make money. This separates it from being an investment instead of an expense.
Try free versions of these tools before buying them since everyone else is.