Quick links (How to make your own NFT contract):

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William Entriken

William Entriken

Mission: Verify seller claims & authenticity for most things you buy

Philadelphia USA / 中国上海

Updated 2023-05-23

Lead author of ERC-721 standard

NFT drops

Art collaborations:


For sale 1/1

The Birth of an Idea

For sale 1/1

All Kindsa Media

For sale 1/1

Golden Landscape

For sale 1/1 0.1 ETH

Ella's Dreams

For sale 1/1

On the road to El Chalten



Su Squares

About 6,500 left to mint

Advisory and vulnerability research

I am the lead author of ERC-721, the document that started NFTs as we know them, and its vision.


My present/past clients include: Arianee, EY, Light.art, Origins NFT, Lucid Sight (MLB Champions), Airbus A³, Dream Syndicate (Rawlings NFT), a checkout processor in the sports/events industry, TreasureDAO, Aleph Crypto Fund, defendant in an investor lawsuit, TRON DAO, a hedge fund.

Code reviews

Some typical design and code review work I have done includes:

Advisory services

I promote intellectual property and stop fraud using blockchain. This standardizes the sale of physical assets on the Ethereum blockchain.

Publicly available to answer your questions each week during NFT/Web3 Community Service Hour and day in and day out on questions websites.

Please see more about advisory services.

ERC-721 lead author since 2018

Privacy Log

I perform technical research of smart contracts and websites. This includes work with the FBI and Apple. Usually I publish these on Privacy Log, and sometimes these publications are live zero-days if the vendor failed to take corrective action. (Of course, I never post zero-days against advisory clients.)

Recent zero-days:

Monthly updates since 2008

Press coverage

Self portraits for media

Speaking events, policy work

I attend events to give workshops and inspire people to act, invite me to your event.

This work was sponsored in part by Ethereum Foundation.

Full product cycles

Here are some products I brought from idea to market. Includes commercial successes, open sourced that you can copy.

19 Questions is a machine learning game that asks you questions about the world.

open source bayesian statistics

Nineteen Eighty-Five is a modern printing of the classic George Orwell book. Orwell’s protagonist battles with his own incriminating #searchhistory, the prying eye of the Social Justice Warriors watching him through his smart device

open source Amazon KDP

SEPTA OTP is my fork of Philadelphia rail schedules which the transit authority has incorporated. It also documents late trains, which you can use to excuse work lateness.

open source patent

Who's the Impostor (谁是卧底) is party word game for 3–12 players. Ranked in top 100 charts for MX, CN, RU.


Light.art NFT drop is a series of NFTs published by high-profile professional photographers. Sold out for 100 Ether in hours.

open source

Echo lets you hear yourself and native speakers to improve pronunciation. This helps with language practice, speech pathology and accent reduction.

open source iOS

23andMe privacy kit by GenoBank anonymizes your DNA collection using physical shuffling and end-to-end encryption.

open source packaging design Ethereum Rinkeby

Formant Analyzer helped my wife improve vowel pronunciation (born in China living in USA) and is useful for speech pathologists.

open source iOS

Su Squares is the first NFT using the ERC-721 standard. This ushered in an era of new applications and enormous media coverage.

open source Ethereum Mainnet

Scribe Academy is one of several online training program launched through Pacific Medical Training and accredited through American Medical Association.

Anasquare is a word puzzle published nationally in GAMES magazine.

open source

System Bus Radio implements an AM radio on computers and phones that do not have radio transmitting hardware. Unclassified implementation of TEMPEST data exfiltration.

open source



My sizes

  • 39L/40L suit
  • 33 slack / 33 inseam
  • 15 1/2 - 34/35 shirt

Best marathon time: 9h : 55m