More on Technology

Jano le Roux
3 years ago
Apple Quietly Introduces A Revolutionary Savings Account That Kills Banks
Would you abandon your bank for Apple?
Banks are struggling.
not as a result of inflation
not due to the economic downturn.
not due to the conflict in Ukraine.
But because they’re underestimating Apple.
Slowly but surely, Apple is looking more like a bank.
An easy new savings account like Apple
Apple has a new savings account.
Apple says Apple Card users may set up and manage savings straight in Wallet.
No more charges
Colorfully high yields
With no minimum balance
No minimal down payments
Most consumer-facing banks will have to match Apple's offer or suffer disruption.
Users may set it up from their iPhones without traveling to a bank or filling out paperwork.
It’s built into the iPhone in your pocket.
So now more waiting for slow approval processes.
Once the savings account is set up, Apple will automatically transfer all future Daily Cash into it. Users may also add these cash to an Apple Cash card in their Apple Wallet app and adjust where Daily Cash is paid at any time.
Apple Pay and Apple Wallet VP Jennifer Bailey:
Savings enables Apple Card users to grow their Daily Cash rewards over time, while also saving for the future.
Bailey says Savings adds value to Apple Card's Daily Cash benefit and offers another easy-to-use tool to help people lead healthier financial lives.
Transfer money from a linked bank account or Apple Cash to a Savings account. Users can withdraw monies to a connected bank account or Apple Cash card without costs.
Once set up, Apple Card customers can track their earnings via Wallet's Savings dashboard. This dashboard shows their account balance and interest.
This product targets younger people as the easiest way to start a savings account on the iPhone.
Why would a Gen Z account holder travel to the bank if their iPhone could be their bank?
Using this concept, Apple will transform the way we think about banking by 2030.
Two other nightmares keep bankers awake at night
Apple revealed two new features in early 2022 that banks and payment gateways hated.
Tap to Pay with Apple
Late Apple Pay
They startled the industry.
Tap To Pay converts iPhones into mobile POS card readers. Apple Pay Later is pushing the BNPL business in a consumer-friendly direction, hopefully ending dodgy lending practices.
Tap to Pay with Apple
iPhone POS
Millions of US merchants, from tiny shops to huge establishments, will be able to accept Apple Pay, contactless credit and debit cards, and other digital wallets with a tap.
No hardware or payment terminal is needed.
Revolutionary!
Stripe has previously launched this feature.
Tap to Pay on iPhone will provide companies with a secure, private, and quick option to take contactless payments and unleash new checkout experiences, said Bailey.
Apple's solution is ingenious. Brilliant!
Bailey says that payment platforms, app developers, and payment networks are making it easier than ever for businesses of all sizes to accept contactless payments and thrive.
I admire that Apple is offering this up to third-party services instead of closing off other functionalities.
Slow POS terminals, farewell.
Late Apple Pay
Pay Apple later.
Apple Pay Later enables US consumers split Apple Pay purchases into four equal payments over six weeks with no interest or fees.
The Apple ecosystem integration makes this BNPL scheme unique. Nonstick. No dumb forms.
Frictionless.
Just double-tap the button.
Apple Pay Later was designed with users' financial well-being in mind. Apple makes it easy to use, track, and pay back Apple Pay Later from Wallet.
Apple Pay Later can be signed up in Wallet or when using Apple Pay. Apple Pay Later can be used online or in an app that takes Apple Pay and leverages the Mastercard network.
Apple Pay Order Tracking helps consumers access detailed receipts and order tracking in Wallet for Apple Pay purchases at participating stores.
Bad BNPL suppliers, goodbye.
Most bankers will be caught in Apple's eye playing mini golf in high-rise offices.
The big problem:
Banks still think about features and big numbers just like other smartphone makers did not too long ago.
Apple thinks about effortlessness, seamlessness, and frictionlessness that just work through integrated hardware and software.
Let me know what you think Apple’s next power moves in the banking industry could be.

Nikhil Vemu
3 years ago
7 Mac Tips You Never Knew You Needed
Unleash the power of the Option key ⌥
#1 Open a link in the Private tab first.
Previously, if I needed to open a Safari link in a private window, I would:
copied the URL with the right click command,
choose File > New Private Window to open a private window, and
clicked return after pasting the URL.
I've found a more straightforward way.
Right-clicking a link shows this, right?
Hold option (⌥) for:
Click Open Link in New Private Window while holding.
Finished!
#2. Instead of searching for specific characters, try this
You may use unicode for business or school. Most people Google them when they need them.
That is lengthy!
You can type some special characters just by pressing ⌥ and a key.
For instance
• ⌥+2 -> ™ (Trademark)
• ⌥+0 -> ° (Degree)
• ⌥+G -> © (Copyright)
• ⌥+= -> ≠ (Not equal to)
• ⌥+< -> ≤ (Less than or equal to)
• ⌥+> -> ≥ (Greater then or equal to)
• ⌥+/ -> ÷ (Different symbol for division)#3 Activate Do Not Disturb silently.
Do Not Disturb when sharing my screen is awkward for me (because people may think Im trying to hide some secret notifications).
Here's another method.
Hold ⌥ and click on Time (at the extreme right on the menu-bar).
Now, DND is activated (secretly!). To turn it off, do it again.
Note: This works only for DND focus.#4. Resize a window starting from its center
Although this is rarely useful, it is still a hidden trick.
When you resize a window, the opposite edge or corner is used as the pivot, right?
However, if you want to resize it with its center as the pivot, hold while doing so.
#5. Yes, Cut-Paste is available on Macs as well (though it is slightly different).
I call it copy-move rather than cut-paste. This is how it works.
Carry it out.
Choose a file (by clicking on it), then copy it (⌘+C).
Go to a new location on your Mac. Do you use ⌘+V to paste it? However, to move it, press ⌘+⌥+V.
This removes the file from its original location and copies it here. And it works exactly like cut-and-paste on Windows.
#6. Instantly expand all folders
Set your Mac's folders to List view.
Assume you have one folder with multiple subfolders, each of which contains multiple files. And you wanted to look at every single file that was over there.
How would you do?
You're used to clicking the ⌄ glyph near the folder and each subfolder to expand them all, right? Instead, hold down ⌥ while clicking ⌄ on the parent folder.
This is what happens next.
Everything expands.
View/Copy a file's path as an added bonus
If you want to see the path of a file in Finder, select it and hold ⌥, and you'll see it at the bottom for a moment.
To copy its path, right-click on the folder and hold down ⌥ to see this
Click on Copy <"folder name"> as Pathname to do it.
#7 "Save As"
I was irritated by the lack of "Save As" in Pages when I first got a Mac (after 15 years of being a Windows guy).
It was necessary for me to save the file as a new file, in a different location, with a different name, or both.
Unfortunately, I couldn't do it on a Mac.
However, I recently discovered that it appears when you hold ⌥ when in the File menu.
Yay!
Colin Faife
3 years ago
The brand-new USB Rubber Ducky is much riskier than before.
The brand-new USB Rubber Ducky is much riskier than before.
With its own programming language, the well-liked hacking tool may now pwn you.
With a vengeance, the USB Rubber Ducky is back.
This year's Def Con hacking conference saw the release of a new version of the well-liked hacking tool, and its author, Darren Kitchen, was on hand to explain it. We put a few of the new features to the test and discovered that the most recent version is riskier than ever.
WHAT IS IT?
The USB Rubber Ducky seems to the untrained eye to be an ordinary USB flash drive. However, when you connect it to a computer, the computer recognizes it as a USB keyboard and will accept keystroke commands from the device exactly like a person would type them in.
Kitchen explained to me, "It takes use of the trust model built in, where computers have been taught to trust a human, in that anything it types is trusted to the same degree as the user is trusted. And a computer is aware that clicks and keystrokes are how people generally connect with it.
Over ten years ago, the first Rubber Ducky was published, quickly becoming a hacker favorite (it was even featured in a Mr. Robot scene). Since then, there have been a number of small upgrades, but the most recent Rubber Ducky takes a giant step ahead with a number of new features that significantly increase its flexibility and capability.
WHERE IS ITS USE?
The options are nearly unlimited with the proper strategy.
The Rubber Ducky has already been used to launch attacks including making a phony Windows pop-up window to collect a user's login information or tricking Chrome into sending all saved passwords to an attacker's web server. However, these attacks lacked the adaptability to operate across platforms and had to be specifically designed for particular operating systems and software versions.
The nuances of DuckyScript 3.0 are described in a new manual.
The most recent Rubber Ducky seeks to get around these restrictions. The DuckyScript programming language, which is used to construct the commands that the Rubber Ducky will enter into a target machine, receives a significant improvement with it. DuckyScript 3.0 is a feature-rich language that allows users to write functions, store variables, and apply logic flow controls, in contrast to earlier versions that were primarily limited to scripting keystroke sequences (i.e., if this... then that).
This implies that, for instance, the new Ducky can check to see if it is hooked into a Windows or Mac computer and then conditionally run code specific to each one, or it can disable itself if it has been attached to the incorrect target. In order to provide a more human effect, it can also generate pseudorandom numbers and utilize them to add a configurable delay between keystrokes.
The ability to steal data from a target computer by encoding it in binary code and transferring it through the signals intended to instruct a keyboard when the CapsLock or NumLock LEDs should light up is perhaps its most astounding feature. By using this technique, a hacker may plug it in for a brief period of time, excuse themselves by saying, "Sorry, I think that USB drive is faulty," and then take it away with all the credentials stored on it.
HOW SERIOUS IS THE RISK?
In other words, it may be a significant one, but because physical device access is required, the majority of people aren't at risk of being a target.
The 500 or so new Rubber Duckies that Hak5 brought to Def Con, according to Kitchen, were his company's most popular item at the convention, and they were all gone on the first day. It's safe to suppose that hundreds of hackers already possess one, and demand is likely to persist for some time.
Additionally, it has an online development toolkit that can be used to create attack payloads, compile them, and then load them onto the target device. A "payload hub" part of the website makes it simple for hackers to share what they've generated, and the Hak5 Discord is also busy with conversation and helpful advice. This makes it simple for users of the product to connect with a larger community.
It's too expensive for most individuals to distribute in volume, so unless your favorite cafe is renowned for being a hangout among vulnerable targets, it's doubtful that someone will leave a few of them there. To that end, if you intend to plug in a USB device that you discovered outside in a public area, pause to consider your decision.
WOULD IT WORK FOR ME?
Although the device is quite straightforward to use, there are a few things that could cause you trouble if you have no prior expertise writing or debugging code. For a while, during testing on a Mac, I was unable to get the Ducky to press the F4 key to activate the launchpad, but after forcing it to identify itself using an alternative Apple keyboard device ID, the problem was resolved.
From there, I was able to create a script that, when the Ducky was plugged in, would instantly run Chrome, open a new browser tab, and then immediately close it once more without requiring any action from the laptop user. Not bad for only a few hours of testing, and something that could be readily changed to perform duties other than reading technology news.
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Tim Denning
3 years ago
Elon Musk’s Rich Life Is a Nightmare
I'm sure you haven't read about Elon's other side.
Elon divorced badly.
Nobody's surprised.
Imagine you're a parent. Someone isn't home year-round. What's next?
That’s what happened to YOLO Elon.
He can do anything. He can intervene in wars, shoot his mouth off, bang anyone he wants, avoid tax, make cool tech, buy anything his ego desires, and live anywhere exotic.
Few know his billionaire backstory. I'll tell you so you don't worship his lifestyle. It’s a cult.
Only his career succeeds. His life is a nightmare otherwise.
Psychopaths' schedule
Elon has said he works 120-hour weeks.
As he told the reporter about his job, he choked up, which was unusual for him.
His crazy workload and lack of sleep forced him to scold innocent Wall Street analysts. Later, he apologized.
In the same interview, he admits he hadn't taken more than a week off since 2001, when he was bedridden with malaria. Elon stays home after a near-death experience.
He's rarely outside.
Elon says he sometimes works 3 or 4 days straight.
He admits his crazy work schedule has cost him time with his kids and friends.
Elon's a slave
Elon's birthday description made him emotional.
Elon worked his entire birthday.
"No friends, nothing," he said, stuttering.
His brother's wedding in Catalonia was 48 hours after his birthday. That meant flying there from Tesla's factory prison.
He arrived two hours before the big moment, barely enough time to eat and change, let alone see his brother.
Elon had to leave after the bouquet was tossed to a crowd of billionaire lovers. He missed his brother's first dance with his wife.
Shocking.
He went straight to Tesla's prison.
The looming health crisis
Elon was asked if overworking affected his health.
Not great. Friends are worried.
Now you know why Elon tweets dumb things. Working so hard has probably caused him mental health issues.
Mental illness removed my reality filter. You do stupid things because you're tired.
Astronauts pelted Elon
Elon's overwork isn't the first time his life has made him emotional.
When asked about Neil Armstrong and Gene Cernan criticizing his SpaceX missions, he got emotional. Elon's heroes.
They're why he started the company, and they mocked his work. In another interview, we see how Elon’s business obsession has knifed him in the heart.
Once you have a company, you must feed, nurse, and care for it, even if it destroys you.
"Yep," Elon says, tearing up.
In the same interview, he's asked how Tesla survived the 2008 recession. Elon stopped the interview because he was crying. When Tesla and SpaceX filed for bankruptcy in 2008, he nearly had a nervous breakdown. He called them his "children."
All the time, he's risking everything.
Jack Raines explains best:
Too much money makes you a slave to your net worth.
Elon's emotions are admirable. It's one of the few times he seems human, not like an alien Cyborg.
Stop idealizing Elon's lifestyle
Building a side business that becomes a billion-dollar unicorn startup is a nightmare.
"Billionaire" means financially wealthy but otherwise broke. A rich life includes more than business and money.
This post is a summary. Read full article here

Julie Plavnik
3 years ago
How to Become a Crypto Broker [Complying and Making Money]
Three options exist. The third one is the quickest and most fruitful.
You've mastered crypto trading and want to become a broker.
So you may wonder: Where to begin?
If so, keep reading.
Today I'll compare three different approaches to becoming a cryptocurrency trader.
What are cryptocurrency brokers, and how do they vary from stockbrokers?
A stockbroker implements clients' market orders (retail or institutional ones).
Brokerage firms are regulated, insured, and subject to regulatory monitoring.
Stockbrokers are required between buyers and sellers. They can't trade without a broker. To trade, a trader must open a broker account and deposit money. When a trader shops, he tells his broker what orders to place.
Crypto brokerage is trade intermediation with cryptocurrency.
In crypto trading, however, brokers are optional.
Crypto exchanges offer direct transactions. Open an exchange account (no broker needed) and make a deposit.
Question:
Since crypto allows DIY trading, why use a broker?
Let's compare cryptocurrency exchanges vs. brokers.
Broker versus cryptocurrency exchange
Most existing crypto exchanges are basically brokers.
Examine their primary services:
connecting purchasers and suppliers
having custody of clients' money (with the exception of decentralized cryptocurrency exchanges),
clearance of transactions.
Brokerage is comparable, don't you think?
There are exceptions. I mean a few large crypto exchanges that follow the stock exchange paradigm. They outsource brokerage, custody, and clearing operations. Classic exchange setups are rare in today's bitcoin industry.
Back to our favorite “standard” crypto exchanges. All-in-one exchanges and brokers. And usually, they operate under a broker or a broker-dealer license, save for the exchanges registered somewhere in a free-trade offshore paradise. Those don’t bother with any licensing.
What’s the sense of having two brokers at a time?
Better liquidity and trading convenience.
The crypto business is compartmentalized.
We have CEXs, DEXs, hybrid exchanges, and semi-exchanges (those that aggregate liquidity but do not execute orders on their sides). All have unique regulations and act as sovereign states.
There are about 18k coins and hundreds of blockchain protocols, most of which are heterogeneous (i.e., different in design and not interoperable).
A trader must register many accounts on different exchanges, deposit funds, and manage them all concurrently to access global crypto liquidity.
It’s extremely inconvenient.
Crypto liquidity fragmentation is the largest obstacle and bottleneck blocking crypto from mass adoption.
Crypto brokers help clients solve this challenge by providing one-gate access to deep and diverse crypto liquidity from numerous exchanges and suppliers. Professionals and institutions need it.
Another killer feature of a brokerage may be allowing clients to trade crypto with fiat funds exclusively, without fiat/crypto conversion. It is essential for professional and institutional traders.
Who may work as a cryptocurrency broker?
Apparently, not anyone. Brokerage requires high-powered specialists because it involves other people's money.
Here's the essentials:
excellent knowledge, skills, and years of trading experience
high-quality, quick, and secure infrastructure
highly developed team
outstanding trading capital
High-ROI network: long-standing, trustworthy connections with customers, exchanges, liquidity providers, payment gates, and similar entities
outstanding marketing and commercial development skills.
What about a license for a cryptocurrency broker? Is it necessary?
Complex question.
If you plan to play in white-glove jurisdictions, you may need a license. For example, in the US, as a “money transmitter” or as a CASSP (crypto asset secondary services provider) in Australia.
Even in these jurisdictions, there are no clear, holistic crypto brokerage and licensing policies.
Your lawyer will help you decide if your crypto brokerage needs a license.
Getting a license isn't quick. Two years of patience are needed.
How can you turn into a cryptocurrency broker?
Finally, we got there! 🎉
Three actionable ways exist:
To kickstart a regulated stand-alone crypto broker
To get a crypto broker franchise, and
To become a liquidity network broker.
Let's examine each.
1. Opening a regulated cryptocurrency broker
It's difficult. Especially If you're targeting first-world users.
You must comply with many regulatory, technical, financial, HR, and reporting obligations to keep your organization running. Some are mentioned above.
The licensing process depends on the products you want to offer (spots or derivatives) and the geographic areas you plan to service. There are no general rules for that.
In an overgeneralized way, here are the boxes you will have to check:
capital availability (usually a large amount of capital c is required)
You will have to move some of your team members to the nation providing the license in order to establish an office presence there.
the core team with the necessary professional training (especially applies to CEO, Head of Trading, Assistant to Head of Trading, etc.)
insurance
infrastructure that is trustworthy and secure
adopted proper AML/KYC/financial monitoring policies, etc.
Assuming you passed, what's next?
I bet it won’t be mind-blowing for you that the license is just a part of the deal. It won't attract clients or revenue.
To bring in high-dollar clientele, you must be a killer marketer and seller. It's not easy to convince people to give you money.
You'll need to be a great business developer to form successful, long-term agreements with exchanges (ideally for no fees), liquidity providers, banks, payment gates, etc. Persuade clients.
It's a tough job, isn't it?
I expect a Quora-type question here:
Can I start an unlicensed crypto broker?
Well, there is always a workaround with crypto!
You can register your broker in a free-trade zone like Seychelles to avoid US and other markets with strong watchdogs.
This is neither wise nor sustainable.
First, such experiments are illegal.
Second, you'll have trouble attracting clients and strategic partners.
A license equals trust. That’s it.
Even a pseudo-license from Mauritius matters.
Here are this method's benefits and downsides.
Cons first.
As you navigate this difficult and expensive legal process, you run the risk of missing out on business prospects. It's quite simple to become excellent compliance yet unable to work. Because your competitors are already courting potential customers while you are focusing all of your effort on paperwork.
Only God knows how long it will take you to pass the break-even point when everything with the license has been completed.
It is a money-burning business, especially in the beginning when the majority of your expenses will go toward marketing, sales, and maintaining license requirements. Make sure you have the fortitude and resources necessary to face such a difficult challenge.
Pros
It may eventually develop into a tool for making money. Because big guys who are professionals at trading require a white-glove regulated brokerage. You have every possibility if you work hard in the areas of sales, marketing, business development, and wealth. Simply put, everything must align.
Launching a regulated crypto broker is analogous to launching a crypto exchange. It's ROUGH. Sure you can take it?
2. Franchise for Crypto Broker (Crypto Sub-Brokerage)
A broker franchise is easier and faster than becoming a regulated crypto broker. Not a traditional brokerage.
A broker franchisee, often termed a sub-broker, joins with a broker (a franchisor) to bring them new clients. Sub-brokers market a broker's products and services to clients.
Sub-brokers are the middlemen between a broker and an investor.
Why is sub-brokering easier?
less demanding qualifications and legal complexity. All you need to do is keep a few certificates on hand (each time depends on the jurisdiction).
No significant investment is required
there is no demand that you be a trading member of an exchange, etc.
As a sub-broker, you can do identical duties without as many rights and certifications.
What about the crypto broker franchise?
Sub-brokers aren't common in crypto.
In most existing examples (PayBito, PCEX, etc.), franchises are offered by crypto exchanges, not brokers. Though we remember that crypto exchanges are, in fact, brokers, do we?
Similarly:
For a commission, a franchiser crypto broker receives new leads from a crypto sub-broker.
See above for why enrolling is easy.
Finding clients is difficult. Most crypto traders prefer to buy-sell on their own or through brokers over sub-broker franchises.
3. Broker of the Crypto Trading Network (or a Network Broker)
It's the greatest approach to execute crypto brokerage, based on effort/return.
Network broker isn't an established word. I wrote it for clarity.
Remember how we called crypto liquidity fragmentation the current crypto finance paradigm's main bottleneck?
Where there's a challenge, there's progress.
Several well-funded projects are aiming to fix crypto liquidity fragmentation. Instead of launching another crypto exchange with siloed trading, the greatest minds create trading networks that aggregate crypto liquidity from desynchronized sources and enable quick, safe, and affordable cross-blockchain transactions. Each project offers a distinct option for users.
Crypto liquidity implies:
One-account access to cryptocurrency liquidity pooled from network participants' exchanges and other liquidity sources
compiled price feeds
Cross-chain transactions that are quick and inexpensive, even for HFTs
link between participants of all kinds, and
interoperability among diverse blockchains
Fast, diversified, and cheap global crypto trading from one account.
How does a trading network help cryptocurrency brokers?
I’ll explain it, taking Yellow Network as an example.
Yellow provides decentralized Layer-3 peer-to-peer trading.
trade across chains globally with real-time settlement and
Between cryptocurrency exchanges, brokers, trading companies, and other sorts of network members, there is communication and the exchange of financial information.
Have you ever heard about ECN (electronic communication network)? If not, it's an automated system that automatically matches buy and sell orders. Yellow is a decentralized digital asset ECN.
Brokers can:
Start trading right now without having to meet stringent requirements; all you need to do is integrate with Yellow Protocol and successfully complete some KYC verification.
Access global aggregated crypto liquidity through a single point.
B2B (Broker to Broker) liquidity channels that provide peer liquidity from other brokers. Orders from the other broker will appear in the order book of a broker who is peering with another broker on the market. It will enable a broker to broaden his offer and raise the total amount of liquidity that is available to his clients.
Select a custodian or use non-custodial practices.
Comparing network crypto brokerage to other types:
A licensed stand-alone brokerage business is much more difficult and time-consuming to launch than network brokerage, and
Network brokerage, in contrast to crypto sub-brokerage, is scalable, independent, and offers limitless possibilities for revenue generation.
Yellow Network Whitepaper. has more details on how to start a brokerage business and what rewards you'll obtain.
Final thoughts
There are three ways to become a cryptocurrency broker, including the non-conventional liquidity network brokerage. The last option appears time/cost-effective.
Crypto brokerage isn't crowded yet. Act quickly to find your right place in this market.
Choose the way that works for you best and see you in crypto trading.
Discover Web3 & DeFi with Yellow Network!
Yellow, powered by Openware, is developing a cross-chain P2P liquidity aggregator to unite the crypto sector and provide global remittance services that aid people.
Join the Yellow Community and plunge into this decade's biggest product-oriented crypto project.
Observe Yellow Twitter
Enroll in Yellow Telegram
Visit Yellow Discord.
On Hacker Noon, look us up.
Yellow Network will expose development, technology, developer tools, crypto brokerage nodes software, and community liquidity mining.

Vitalik
4 years ago
An approximate introduction to how zk-SNARKs are possible (part 1)
You can make a proof for the statement "I know a secret number such that if you take the word ‘cow', add the number to the end, and SHA256 hash it 100 million times, the output starts with 0x57d00485aa". The verifier can verify the proof far more quickly than it would take for them to run 100 million hashes themselves, and the proof would also not reveal what the secret number is.
In the context of blockchains, this has 2 very powerful applications: Perhaps the most powerful cryptographic technology to come out of the last decade is general-purpose succinct zero knowledge proofs, usually called zk-SNARKs ("zero knowledge succinct arguments of knowledge"). A zk-SNARK allows you to generate a proof that some computation has some particular output, in such a way that the proof can be verified extremely quickly even if the underlying computation takes a very long time to run. The "ZK" part adds an additional feature: the proof can keep some of the inputs to the computation hidden.
You can make a proof for the statement "I know a secret number such that if you take the word ‘cow', add the number to the end, and SHA256 hash it 100 million times, the output starts with 0x57d00485aa". The verifier can verify the proof far more quickly than it would take for them to run 100 million hashes themselves, and the proof would also not reveal what the secret number is.
In the context of blockchains, this has two very powerful applications:
- Scalability: if a block takes a long time to verify, one person can verify it and generate a proof, and everyone else can just quickly verify the proof instead
- Privacy: you can prove that you have the right to transfer some asset (you received it, and you didn't already transfer it) without revealing the link to which asset you received. This ensures security without unduly leaking information about who is transacting with whom to the public.
But zk-SNARKs are quite complex; indeed, as recently as in 2014-17 they were still frequently called "moon math". The good news is that since then, the protocols have become simpler and our understanding of them has become much better. This post will try to explain how ZK-SNARKs work, in a way that should be understandable to someone with a medium level of understanding of mathematics.
Why ZK-SNARKs "should" be hard
Let us take the example that we started with: we have a number (we can encode "cow" followed by the secret input as an integer), we take the SHA256 hash of that number, then we do that again another 99,999,999 times, we get the output, and we check what its starting digits are. This is a huge computation.
A "succinct" proof is one where both the size of the proof and the time required to verify it grow much more slowly than the computation to be verified. If we want a "succinct" proof, we cannot require the verifier to do some work per round of hashing (because then the verification time would be proportional to the computation). Instead, the verifier must somehow check the whole computation without peeking into each individual piece of the computation.
One natural technique is random sampling: how about we just have the verifier peek into the computation in 500 different places, check that those parts are correct, and if all 500 checks pass then assume that the rest of the computation must with high probability be fine, too?
Such a procedure could even be turned into a non-interactive proof using the Fiat-Shamir heuristic: the prover computes a Merkle root of the computation, uses the Merkle root to pseudorandomly choose 500 indices, and provides the 500 corresponding Merkle branches of the data. The key idea is that the prover does not know which branches they will need to reveal until they have already "committed to" the data. If a malicious prover tries to fudge the data after learning which indices are going to be checked, that would change the Merkle root, which would result in a new set of random indices, which would require fudging the data again... trapping the malicious prover in an endless cycle.
But unfortunately there is a fatal flaw in naively applying random sampling to spot-check a computation in this way: computation is inherently fragile. If a malicious prover flips one bit somewhere in the middle of a computation, they can make it give a completely different result, and a random sampling verifier would almost never find out.
It only takes one deliberately inserted error, that a random check would almost never catch, to make a computation give a completely incorrect result.
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? There is a clever solution.
see part 2
