More on Marketing

Francesca Furchtgott
3 years ago
Giving customers what they want or betraying the values of the brand?
A J.Crew collaboration for fashion label Eveliina Vintage is not a paradox; it is a solution.
Eveliina Vintage's capsule collection debuted yesterday at J.Crew. This J.Crew partnership stopped me in my tracks.
Eveliina Vintage sells vintage goods. Eeva Musacchia founded the shop in Finland in the 1970s. It's recognized for its one-of-a-kind slip dresses from the 1930s and 1940s.
I wondered why a vintage brand would partner with a mass shop. Fast fashion against vintage shopping? Will Eveliina Vintages customers be turned off?
But Eveliina Vintages customers don't care about sustainability. They want Eveliina's Instagram look. Eveliina Vintage collaborated with J.Crew to give customers what they wanted: more Eveliina at a lower price.
Vintage: A Fashion Option That Is Eco-Conscious
Secondhand shopping is a trendy response to quick fashion. J.Crew releases hundreds of styles annually. Waste and environmental damage have been criticized. A pair of jeans requires 1,800 gallons of water. J.Crew's limited-time deals promote more purchases. J.Crew items are likely among those Americans wear 7 times before discarding.
Consumers and designers have emphasized sustainability in recent years. Stella McCartney and Eileen Fisher are popular eco-friendly brands. They've also flocked to ThredUp and similar sites.
Gap, Levis, and Allbirds have listened to consumer requests. They promote recycling, ethical sourcing, and secondhand shopping.
Secondhand shoppers feel good about reusing and recycling clothing that might have ended up in a landfill.
Eco-conscious fashionistas shop vintage. These shoppers enjoy the thrill of the hunt (that limited-edition Chanel bag!) and showing off a unique piece (nobody will have my look!). They also reduce their environmental impact.
Is Eveliina Vintage capitalizing on an aesthetic or is it a sustainable brand?
Eveliina Vintage emphasizes environmental responsibility. Vogue's Amanda Musacchia emphasized sustainability. Amanda, founder Eeva's daughter, is a company leader.
But Eveliina's press message doesn't address sustainability, unlike Instagram. Scarcity and fame rule.
Eveliina Vintages Instagram has see-through dresses and lace-trimmed slip dresses. Celebrities and influencers are often photographed in Eveliina's apparel, which has 53,000+ followers. Vogue appreciates Eveliina's style. Multiple publications discuss Alexa Chung's Eveliina dress.
Eveliina Vintage markets its one-of-a-kind goods. It teases future content, encouraging visitors to return. Scarcity drives demand and raises clothing prices. One dress is $1,600+, but most are $500-$1,000.
The catch: Eveliina can't monetize its expanding popularity due to exorbitant prices and limited quantity. Why?
Most people struggle to pay for their clothing. But Eveliina Vintage lacks those more affordable entry-level products, in contrast to other luxury labels that sell accessories or perfume.
Many people have trouble fitting into their clothing. The bodies of most women in the past were different from those for which vintage clothing was designed. Each Eveliina dress's specific measurements are mentioned alongside it. Be careful, you can fall in love with an ill-fitting dress.
No matter how many people can afford it and fit into it, there is only one item to sell. To get the item before someone else does, those people must be on the Eveliina Vintage website as soon as it becomes available.
A Way for Eveliina Vintage to Make Money (and Expand) with J.Crew Its following
Eveliina Vintages' cooperation with J.Crew makes commercial sense.
This partnership spreads Eveliina's style. Slightly better pricing The $390 outfits have multicolored slips and gauzy cotton gowns. Sizes range from 00 to 24, which is wider than vintage racks.
Eveliina Vintage customers like the combination. Excited comments flood the brand's Instagram launch post. Nobody is mocking the 50-year-old vintage brand's fast-fashion partnership.
Vintage may be a sustainable fashion trend, but that's not why Eveliina's clients love the brand. They only care about the old look.
And that is a tale as old as fashion.
Guillaume Dumortier
2 years ago
Mastering the Art of Rhetoric: A Guide to Rhetorical Devices in Successful Headlines and Titles
Unleash the power of persuasion and captivate your audience with compelling headlines.
As the old adage goes, "You never get a second chance to make a first impression."
In the world of content creation and social ads, headlines and titles play a critical role in making that first impression.
A well-crafted headline can make the difference between an article being read or ignored, a video being clicked on or bypassed, or a product being purchased or passed over.
To make an impact with your headlines, mastering the art of rhetoric is essential. In this post, we'll explore various rhetorical devices and techniques that can help you create headlines that captivate your audience and drive engagement.
tl;dr : Headline Magician will help you craft the ultimate headline titles powered by rhetoric devices
Example with a high-end luxury organic zero-waste skincare brand
✍️ The Power of Alliteration
Alliteration is the repetition of the same consonant sound at the beginning of words in close proximity. This rhetorical device lends itself well to headlines, as it creates a memorable, rhythmic quality that can catch a reader's attention.
By using alliteration, you can make your headlines more engaging and easier to remember.
Examples:
"Crafting Compelling Content: A Comprehensive Course"
"Mastering the Art of Memorable Marketing"
🔁 The Appeal of Anaphora
Anaphora is the repetition of a word or phrase at the beginning of successive clauses. This rhetorical device emphasizes a particular idea or theme, making it more memorable and persuasive.
In headlines, anaphora can be used to create a sense of unity and coherence, which can draw readers in and pique their interest.
Examples:
"Create, Curate, Captivate: Your Guide to Social Media Success"
"Innovation, Inspiration, and Insight: The Future of AI"
🔄 The Intrigue of Inversion
Inversion is a rhetorical device where the normal order of words is reversed, often to create an emphasis or achieve a specific effect.
In headlines, inversion can generate curiosity and surprise, compelling readers to explore further.
Examples:
"Beneath the Surface: A Deep Dive into Ocean Conservation"
"Beyond the Stars: The Quest for Extraterrestrial Life"
⚖️ The Persuasive Power of Parallelism
Parallelism is a rhetorical device that involves using similar grammatical structures or patterns to create a sense of balance and symmetry.
In headlines, parallelism can make your message more memorable and impactful, as it creates a pleasing rhythm and flow that can resonate with readers.
Examples:
"Eat Well, Live Well, Be Well: The Ultimate Guide to Wellness"
"Learn, Lead, and Launch: A Blueprint for Entrepreneurial Success"
⏭️ The Emphasis of Ellipsis
Ellipsis is the omission of words, typically indicated by three periods (...), which suggests that there is more to the story.
In headlines, ellipses can create a sense of mystery and intrigue, enticing readers to click and discover what lies behind the headline.
Examples:
"The Secret to Success... Revealed"
"Unlocking the Power of Your Mind... A Step-by-Step Guide"
🎭 The Drama of Hyperbole
Hyperbole is a rhetorical device that involves exaggeration for emphasis or effect.
In headlines, hyperbole can grab the reader's attention by making bold, provocative claims that stand out from the competition. Be cautious with hyperbole, however, as overuse or excessive exaggeration can damage your credibility.
Examples:
"The Ultimate Guide to Mastering Any Skill in Record Time"
"Discover the Revolutionary Technique That Will Transform Your Life"
❓The Curiosity of Questions
Posing questions in your headlines can be an effective way to pique the reader's curiosity and encourage engagement.
Questions compel the reader to seek answers, making them more likely to click on your content. Additionally, questions can create a sense of connection between the content creator and the audience, fostering a sense of dialogue and discussion.
Examples:
"Are You Making These Common Mistakes in Your Marketing Strategy?"
"What's the Secret to Unlocking Your Creative Potential?"
💥 The Impact of Imperatives
Imperatives are commands or instructions that urge the reader to take action. By using imperatives in your headlines, you can create a sense of urgency and importance, making your content more compelling and actionable.
Examples:
"Master Your Time Management Skills Today"
"Transform Your Business with These Innovative Strategies"
💢 The Emotion of Exclamations
Exclamations are powerful rhetorical devices that can evoke strong emotions and convey a sense of excitement or urgency.
Including exclamations in your headlines can make them more attention-grabbing and shareable, increasing the chances of your content being read and circulated.
Examples:
"Unlock Your True Potential: Find Your Passion and Thrive!"
"Experience the Adventure of a Lifetime: Travel the World on a Budget!"
🎀 The Effectiveness of Euphemisms
Euphemisms are polite or indirect expressions used in place of harsher, more direct language.
In headlines, euphemisms can make your message more appealing and relatable, helping to soften potentially controversial or sensitive topics.
Examples:
"Navigating the Challenges of Modern Parenting"
"Redefining Success in a Fast-Paced World"
⚡Antithesis: The Power of Opposites
Antithesis involves placing two opposite words side-by-side, emphasizing their contrasts. This device can create a sense of tension and intrigue in headlines.
Examples:
"Once a day. Every day"
"Soft on skin. Kill germs"
"Mega power. Mini size."
To utilize antithesis, identify two opposing concepts related to your content and present them in a balanced manner.
🎨 Scesis Onomaton: The Art of Verbless Copy
Scesis onomaton is a rhetorical device that involves writing verbless copy, which quickens the pace and adds emphasis.
Example:
"7 days. 7 dollars. Full access."
To use scesis onomaton, remove verbs and focus on the essential elements of your headline.
🌟 Polyptoton: The Charm of Shared Roots
Polyptoton is the repeated use of words that share the same root, bewitching words into memorable phrases.
Examples:
"Real bread isn't made in factories. It's baked in bakeries"
"Lose your knack for losing things."
To employ polyptoton, identify words with shared roots that are relevant to your content.
✨ Asyndeton: The Elegance of Omission
Asyndeton involves the intentional omission of conjunctions, adding crispness, conviction, and elegance to your headlines.
Examples:
"You, Me, Sushi?"
"All the latte art, none of the environmental impact."
To use asyndeton, eliminate conjunctions and focus on the core message of your headline.
🔮 Tricolon: The Magic of Threes
Tricolon is a rhetorical device that uses the power of three, creating memorable and impactful headlines.
Examples:
"Show it, say it, send it"
"Eat Well, Live Well, Be Well."
To use tricolon, craft a headline with three key elements that emphasize your content's main message.
🔔 Epistrophe: The Chime of Repetition
Epistrophe involves the repetition of words or phrases at the end of successive clauses, adding a chime to your headlines.
Examples:
"Catch it. Bin it. Kill it."
"Joint friendly. Climate friendly. Family friendly."
To employ epistrophe, repeat a key phrase or word at the end of each clause.

Michael Salim
3 years ago
300 Signups, 1 Landing Page, 0 Products
I placed a link on HackerNews and got 300 signups in a week. This post explains what happened.
Product Concept
The product is DbSchemaLibrary. A library of Database Schema.
I'm not sure where this idea originated from. Very fast. Build fast, fail fast, test many ideas, and one will be a hit. I tried it. Let's try it anyway, even though it'll probably fail. I finished The Lean Startup book and wanted to use it.
Database job bores me. Important! I get drowsy working on it. Someone must do it. I remember this happening once. I needed examples at the time. Something similar to Recall (my other project) that I can copy — or at least use as a reference.
Frequently googled. Many tabs open. The results were useless. I raised my hand and agreed to construct the database myself.
It resurfaced. I decided to do something.
Due Diligence
Lean Startup emphasizes validated learning. Everything the startup does should result in learning. I may build something nobody wants otherwise. That's what happened to Recall.
So, I wrote a business plan document. This happens before I code. What am I solving? What is my proposed solution? What is the leap of faith between the problem and solution? Who would be my target audience?
My note:
In my previous project, I did the opposite!
I wrote my expectations after reading the book's advice.
“Failure is a prerequisite to learning. The problem with the notion of shipping a product and then seeing what happens is that you are guaranteed to succeed — at seeing what happens.” — The Lean Startup book
These are successful metrics. If I don't reach them, I'll drop the idea and try another. I didn't understand numbers then. Below are guesses. But it’s a start!
I then wrote the project's What and Why. I'll use this everywhere. Before, I wrote a different pitch each time. I thought certain words would be better. I felt the audience might want something unusual.
Occasionally, this works. I'm unsure if it's a good idea. No stats, just my writing-time opinion. Writing every time is time-consuming and sometimes hazardous. Having a copy saved me duplication.
I can measure and learn from performance.
Last, I identified communities that might demand the product. This became an exercise in creativity.
The MVP
So now it’s time to build.
A MVP can test my assumptions. Business may learn from it. Not low-quality. We should learn from the tiniest thing.
I like the example of how Dropbox did theirs. They assumed that if the product works, people will utilize it. How can this be tested without a quality product? They made a movie demonstrating the software's functionality. Who knows how much functionality existed?
So I tested my biggest assumption. Users want schema references. How can I test if users want to reference another schema? I'd love this. Recall taught me that wanting something doesn't mean others do.
I made an email-collection landing page. Describe it briefly. Reference library. Each email sender wants a reference. They're interested in the product. Few other reasons exist.
Header and footer were skipped. No name or logo. DbSchemaLibrary is a name I thought of after the fact. 5-minute logo. I expected a flop. Recall has no users after months of labor. What could happen to a 2-day project?
I didn't compromise learning validation. How many visitors sign up? To draw a conclusion, I must track these results.
Posting Time
Now that the job is done, gauge interest. The next morning, I posted on all my channels. I didn't want to be spammy, therefore it required more time.
I made sure each channel had at least one fan of this product. I also answer people's inquiries in the channel.
My list stinks. Several channels wouldn't work. The product's target market isn't there. Posting there would waste our time. This taught me to create marketing channels depending on my persona.
Statistics! What actually happened
My favorite part! 23 channels received the link.
I stopped posting to Discord despite its high conversion rate. I eliminated some channels because they didn't fit. According to the numbers, some users like it. Most users think it's spam.
I was skeptical. And 12 people viewed it.
I didn't expect much attention on a startup subreddit. I'll likely examine Reddit further in the future. As I have enough info, I didn't post much. Time for the next validated learning
No comment. The post had few views, therefore the numbers are low.
The targeted people come next.
I'm a Toptal freelancer. There's a member-only Slack channel. Most people can't use this marketing channel, but you should! It's not as spectacular as discord's 27% conversion rate. But I think the users here are better.
I don’t really have a following anywhere so this isn’t something I can leverage.
The best yet. 10% is converted. With more data, I expect to attain a 10% conversion rate from other channels. Stable number.
This number required some work. Did you know that people use many different clients to read HN?
Unknowns
Untrackable views and signups abound. 1136 views and 135 signups are untraceable. It's 11%. I bet much of that came from Hackernews.
Overall Statistics
The 7-day signup-to-visit ratio was 17%. (Hourly data points)
First-day percentages were lower, which is noteworthy. Initially, it was little above 10%. The HN post started getting views then.
When traffic drops, the number reaches just around 20%. More individuals are interested in the connection. hn.algolia.com sent 2 visitors. This means people are searching and finding my post.
Interesting discoveries
1. HN post struggled till the US woke up.
11am UTC. After an hour, it lost popularity. It seemed over. 7 signups converted 13%. Not amazing, but I would've thought ahead.
After 4pm UTC, traffic grew again. 4pm UTC is 9am PDT. US awakened. 10am PDT saw 512 views.
2. The product was highlighted in a newsletter.
I found Revue references when gathering data. Newsletter platform. Someone posted the newsletter link. 37 views and 3 registrations.
3. HN numbers are extremely reliable
I don't have a time-lapse graph (yet). The statistics were constant all day.
2717 views later 272 new users, or 10.1%
With 293 signups at 2856 views, 10.25%
At 306 signups at 2965 views, 10.32%
Learnings
1. My initial estimations were wildly inaccurate
I wrote 30% conversion. Reading some articles, looks like 10% is a good number to aim for.
2. Paying attention to what matters rather than vain metrics
The Lean Startup discourages vanity metrics. Feel-good metrics that don't measure growth or traction. Considering the proportion instead of the total visitors made me realize there was something here.
What’s next?
There are lots of work to do. Data aggregation, display, website development, marketing, legal issues. Fun! It's satisfying to solve an issue rather than investigate its cause.
In the meantime, I’ve already written the first project update in another post. Continue reading it if you’d like to know more about the project itself! Shifting from Quantity to Quality — DbSchemaLibrary
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Michelle Teheux
3 years ago
Get Real, All You Grateful Laid-Off LinkedIn Users
WTF is wrong with you people?
When I was laid off as editor of my town's daily newspaper, I went silent on social media. I knew it was coming and had been quietly removing personal items each day, but the pain was intense.
I posted a day later. I didn't bad-mouth GateHouse Media but expressed my sadness at leaving the newspaper industry, pride in my accomplishments, and hope for success in another industry.
Normal job-loss response.
What do you recognize as abnormal?
The bullshit I’ve been reading from laid-off folks on LinkedIn.
If you're there, you know. Many Twitter or Facebook/Meta employees recently lost their jobs.
Well, many of them did not “lose their job,” actually. They were “impacted by the layoffs” at their former employer. I keep seeing that phrase.
Why don’t they want to actually say it? Why the euphemism?
Many are excited about the opportunities ahead. The jobless deny being sad.
They're ecstatic! They have big plans.
Hope so. Sincerely! Being laid off stinks, especially if, like me, your skills are obsolete. It's worse if, like me, you're too old to start a new career. Ageism exists despite denials.
Nowadays, professionalism seems to demand psychotic levels of fake optimism.
Why? Life is unpredictable. That's indisputable. You shouldn't constantly complain or cry in public, but you also shouldn't pretend everything's great.
It makes you look psychotic, not positive. It's like saying at work:
“I was impacted by the death of my spouse of 20 years this week, and many of you have reached out to me, expressing your sympathy. However, I’m choosing to remember the amazing things we shared. I feel confident that there is another marriage out there for me, and after taking a quiet weekend trip to reset myself, I’ll be out there looking for the next great marital adventure! #staypositive #available #opentolove
Also:
“Now looking for our next #dreamhome after our entire neighborhood was demolished by a wildfire last night. We feel so lucky to have lived near so many amazing and inspirational neighbors, all of whom we will miss as we go on our next housing adventure. The best house for us is yet to come! If you have a great neighborhood you’d recommend, please feel free to reach out and touch base with us! #newhouse #newneighborhood #newlife
Admit it. That’s creepy.
The constant optimism makes me feel sick to my stomach.
Viscerally.
I hate fakes.
Imagine a fake wood grain desk. Wouldn't it be better if the designer accepted that it's plastic and went with that?
Real is better but not always nice. When something isn't nice, you don't have to go into detail, but you also shouldn't pretend it's great.
How to announce your job loss to the world.
Do not pretend to be happy, but don't cry and drink vodka all afternoon.
Say you loved your job, and that you're looking for new opportunities.
Yes, if you'll miss your coworkers. Otherwise, don't badmouth. No bridge-burning!
Please specify the job you want. You may want to pivot.
Alternatively, try this.
You could always flame out.
If you've pushed yourself too far into toxic positivity, you may be ready to burn it all down. If so, make it worthwhile by writing something like this:
Well, I was shitcanned by the losers at #Acme today. That bitch Linda in HR threw me under the bus just because she saw that one of my “friends” tagged me in some beach pics on social media after I called in sick with Covid. The good thing is I will no longer have to watch my ass around that #asspincher Ron in accounting, but I’m sad that I will no longer have a cushy job with high pay or access to the primo office supplies I’ve been sneaking home for the last five years. (Those gel pens were the best!) I am going to be taking some time off to enjoy my unemployment and hammer down shots of Jägermeister but in about five months I’ll be looking for anything easy with high pay and great benefits. Reach out if you can help! #officesupplies #unemploymentrocks #drinkinglikeagirlboss #acmesucks
It beats the fake positivity.

VIP Graphics
3 years ago
Leaked pitch deck for Metas' new influencer-focused live-streaming service
As part of Meta's endeavor to establish an interactive live-streaming platform, the company is testing with influencers.
The NPE (new product experimentation team) has been testing Super since late 2020.
Bloomberg defined Super as a Cameo-inspired FaceTime-like gadget in 2020. The tool has evolved into a Twitch-like live streaming application.
Less than 100 creators have utilized Super: Creators can request access on Meta's website. Super isn't an Instagram, Facebook, or Meta extension.
“It’s a standalone project,” the spokesperson said about Super. “Right now, it’s web only. They have been testing it very quietly for about two years. The end goal [of NPE projects] is ultimately creating the next standalone project that could be part of the Meta family of products.” The spokesperson said the outreach this week was part of a drive to get more creators to test Super.
A 2021 pitch deck from Super reveals the inner workings of Meta.
The deck gathered feedback on possible sponsorship models, with mockups of brand deals & features. Meta reportedly paid creators $200 to $3,000 to test Super for 30 minutes.
Meta's pitch deck for Super live streaming was leaked.
What were the slides in the pitch deck for Metas Super?
Embed not supported: see full deck & article here →
View examples of Meta's pitch deck for Super:
Product Slides, first
The pitch deck begins with Super's mission:
Super is a Facebook-incubated platform which helps content creators connect with their fans digitally, and for super fans to meet and support their favorite creators. In the spirit of Late Night talk shows, we feature creators (“Superstars”), who are guests at a live, hosted conversation moderated by a Host.
This slide (and most of the deck) is text-heavy, with few icons, bullets, and illustrations to break up the content. Super's online app status (which requires no download or installation) might be used as a callout (rather than paragraph-form).
Meta's Super platform focuses on brand sponsorships and native placements, as shown in the slide above.
One of our theses is the idea that creators should benefit monetarily from their Super experiences, and we believe that offering a menu of different monetization strategies will enable the right experience for each creator. Our current focus is exploring sponsorship opportunities for creators, to better understand what types of sponsor placements will facilitate the best experience for all Super customers (viewers, creators, and advertisers).
Colorful mockups help bring Metas vision for Super to life.
2. Slide Features
Super's pitch deck focuses on the platform's features. The deck covers pre-show, pre-roll, and post-event for a Sponsored Experience.
Pre-show: active 30 minutes before the show's start
Pre-roll: Play a 15-minute commercial for the sponsor before the event (auto-plays once)
Meet and Greet: This event can have a branding, such as Meet & Greet presented by [Snickers]
Super Selfies: Makers and followers get a digital souvenir to post on social media.
Post-Event: Possibility to draw viewers' attention to sponsored content/links during the after-show
Almost every screen displays the Sponsor logo, link, and/or branded background. Viewers can watch sponsor video while waiting for the event to start.
Slide 3: Business Model
Meta's presentation for Super is incomplete without numbers. Super's first slide outlines the creator, sponsor, and Super's obligations. Super does not charge creators any fees or commissions on sponsorship earnings.
How to make a great pitch deck
We hope you can use the Super pitch deck to improve your business. Bestpitchdeck.com/super-meta is a bookmarkable link.
You can also use one of our expert-designed templates to generate a pitch deck.
Our team has helped close $100M+ in agreements and funding for premier companies and VC firms. Use our presentation templates, one-pagers, or financial models to launch your pitch.
Every pitch must be audience-specific. Our team has prepared pitch decks for various sectors and fundraising phases.
Pitch Deck Software VIP.graphics produced a popular SaaS & Software Pitch Deck based on decks that closed millions in transactions & investments for orgs of all sizes, from high-growth startups to Fortune 100 enterprises. This easy-to-customize PowerPoint template includes ready-made features and key slides for your software firm.
Accelerator Pitch Deck The Accelerator Pitch Deck template is for early-stage founders seeking funding from pitch contests, accelerators, incubators, angels, or VC companies. Winning a pitch contest or getting into a top accelerator demands a strategic investor pitch.
Pitch Deck Template Series Startup and founder pitch deck template: Workable, smart slides. This pitch deck template is for companies, entrepreneurs, and founders raising seed or Series A finance.
M&A Pitch Deck Perfect Pitch Deck is a template for later-stage enterprises engaging more sophisticated conversations like M&A, late-stage investment (Series C+), or partnerships & funding. Our team prepared this presentation to help creators confidently pitch to investment banks, PE firms, and hedge funds (and vice versa).
Browse our growing variety of industry-specific pitch decks.

Vitalik
3 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
