Bram Cohen

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Lore & Background

Bram Cohen grew up on the Upper West Side of Manhattan, New York City, as the son of a teacher and computer scientist. He claims he learned the BASIC programming language at the age of 5 on his family's Timex Sinclair computer. Cohen passed the American Invitational Mathematics Examination to qualify for the United States of America Mathematical Olympiad while he attended Stuyvesant High School in New York City. He graduated from Stuyvesant in 1993, and attended SUNY Buffalo. He later dropped out of college to work for several dot-com companies throughout the mid-to-late 1990s, the last being MojoNation, an ambitious but ill-fated project he worked on with Jim McCoy. MojoNation allowed people to break up confidential files into encrypted chunks and distribute those pieces on computers also running the software. If someone wanted to download a copy of this encrypted file, they would have to download it simultaneously from many computers. This concept, Cohen thought, was perfect for a file-sharing program, since programs like KaZaA take a long time to download a large file because the file is (usually) coming from one source (or peer). In April 2001, Cohen quit MojoNation and began work on BitTorrent. Cohen unveiled his ideas at the first CodeCon conference, which he and his roommate Len Sassaman created as a showcase event for novel technology projects after becoming disillusioned with the state of then-current technology conferences. Cohen wrote the first BitTorrent client implementation in Python. In the summer of 2002, Cohen collected free pornography to lure beta testers to use the program. In May 2005, Cohen released a trackerless beta version of BitTorrent. Cohen has claimed he has never violated copyright law using his software. In late 2003, Cohen worked for a short time at Valve, working on Steam, their digital distribution system introduced for Half-Life 2. By 2004, he had left Valve and formed BitTorrent, Inc., with his brother Ross Cohen and business partner Ashwin Navin. In 2012, he announced a beta version of BitTorrent Live for TV broadcasting through the Internet. Cohen left BitTorrent, Inc., in a day-to-day capacity to co-found Chia Network in the fall of 2017. Chia Network is a company founded by Cohen in 2017 that has implemented a proof-of-space-time cryptocurrency called Chia (XCH). Chia is intended to avoid the waste of energy involved in proof-of-work-based cryptocurrencies such as Bitcoin, and the vulnerability to state actors of proof-of-stake systems. Chia Network has raised seed money from investors including Andreessen Horowitz. The use of storage media (hard disks and solid-state drives) as the cryptocurrency's mining medium has raised concerns over potential price surges and shortage of high-capacity storage devices, as well as radically reducing the lifetime of drives. As of 2008, Cohen lived in the San Francisco Bay Area of the United States, with his wife Jenna and their three children. The couple divorced in 2022. Cohen says that he has Asperger syndrome based on a self diagnosis. Cohen's hobbies include original origami and juggling up to five balls, but his main interest is in recreational mathematics. Cohen maintains a blog where he frequently discusses trust metrics with software developer Raph Levien, as well as money systems, games of skill, and other math-related topics. He is also an assembly puzzle enthusiast. He has designed several puzzles including some in conjunction with Oskar van Deventer including several gear-based puzzles such as Gear Shift and a multiple Rubik's Cube variant called Bram's Fortress. Some of Cohen's puzzle designs are available for 3-D printing via Shapeways.

Reader's Guide

Bram Cohen's significance lies in his creation of the BitTorrent protocol, which revolutionized file sharing by enabling efficient distribution of large files through peer-to-peer networking. The protocol's design, allowing downloads from many sources simultaneously, sped up download time, especially for users with faster download than upload speeds. Thus, the more popular a file is, the faster a user will be able to download it, since many people will be downloading it at the same time, and these people will also be uploading the data to other users. BitTorrent gained its fame for its ability to quickly share large music and movie files online. Since the early releases, many other programs have implemented the BitTorrent protocol. Cohen's later work on Chia cryptocurrency introduced a novel proof-of-space-time consensus algorithm, aiming to reduce energy consumption compared to Bitcoin while avoiding centralization risks of proof-of-stake systems. His contributions to peer-to-peer technology and cryptocurrency have had lasting impacts on internet infrastructure and digital economics. Cohen's outspoken views on the obsolescence of traditional media business models and his involvement in conferences like CodeCon further shaped the tech community's approach to decentralized systems. Despite controversies over copyright infringement, Cohen maintained he never violated copyright law using his software.

Did You Know?

• Cohen claims he learned the BASIC programming language at age 5 on his family's Timex Sinclair computer.
• In the summer of 2002, Cohen collected free pornography to lure beta testers to use BitTorrent.
• Cohen worked for a short time at Valve in late 2003, working on Steam for Half-Life 2.
• Cohen has designed several gear-based puzzles with Oskar van Deventer, including Gear Shift and a multiple Rubik's Cube variant called Bram's Fortress.
• Cohen says he has Asperger syndrome based on a self diagnosis.

Early Life and the Seeds of an Idea

His relationship with code began almost immediately; he claims he learned the BASIC programming language at the age of 5 on his family's Timex Sinclair computer. That early fluency carried him through Stuyvesant High School, where he passed the American Invitational Mathematics Examination to qualify for the United States of America Mathematical Olympiad. He graduated from Stuyvesant in 1993, and attended SUNY Buffalo. He later dropped out of college to work for several dot-com companies throughout the mid-to-late 1990s, the last being MojoNation, an ambitious but ill-fated project he worked on with Jim McCoy. MojoNation allowed people to break up confidential files into encrypted chunks and distribute those pieces on computers also running the software. If someone wanted to download a copy of this encrypted file, they would have to download it simultaneously from many computers. This concept, Cohen thought, was perfect for a file-sharing program, since programs like KaZaA take a long time to download a large file because the file is (usually) coming from one source (or peer). That realization became the blueprint for everything that followed.

Building BitTorrent and Shaping a New Internet

In April 2001, Cohen quit MojoNation and began work on BitTorrent. He first presented the concept at CodeCon, a showcase conference he and roommate Len Sassaman created out of frustration with the state of then-current technology conferences. Cohen wrote the first BitTorrent client implementation in Python. In the summer of 2002, Cohen collected free pornography to lure beta testers to use the program. In May 2005, Cohen released a trackerless beta version of BitTorrent. Cohen has claimed he has never violated copyright law using his software. Regardless, he is outspoken in his belief that the traditional media business model is doomed to becoming outmoded, despite RIAA's and MPAA's legal and technical tactics, such as digital rights management. In late 2003, Cohen worked for a short time at Valve, working on Steam, their digital distribution system introduced for Half-Life 2. By 2004, he had left Valve and formed BitTorrent, Inc., with his brother Ross Cohen and business partner Ashwin Navin. In 2012, he announced a beta version of BitTorrent Live for TV broadcasting through the Internet. By mid-2005, BitTorrent, Inc., was funded by venture capitalist David Chao from Doll Capital Management, and in late 2005 Cohen and Navin made a deal with the MPAA to remove links to illegal content on the official BitTorrent website. The deal was with the seven largest studios in the United States. The agreement means the site will comply with procedures outlined in the Digital Millennium Copyright Act.

Chia and the Proof-of-Space-Time Vision

Cohen left BitTorrent, Inc., in a day-to-day capacity to co-found Chia Network in the fall of 2017. Chia Network is a company founded by Cohen in 2017 that has implemented a proof-of-space-time cryptocurrency called Chia (XCH). Chia is intended to avoid the waste of energy involved in proof-of-work-based cryptocurrencies such as Bitcoin, and the vulnerability to state actors of proof-of-stake systems. The model attracted seed investment from investors including Andreessen Horowitz. Yet the approach also drew criticism. The use of storage media (hard disks and solid-state drives) as the cryptocurrency's mining medium has raised concerns over potential price surges and shortage of high-capacity storage devices, as well as radically reducing the lifetime of drives.

The Puzzle Maker and the Private Life

Beyond the protocol that reshaped file distribution, Cohen has always been drawn to the playful side of mathematics and mechanics. He describes his main intellectual passion as recreational mathematics, a thread that runs through his blog—where he and software developer Raph Levien discuss trust metrics, money systems, games of skill, and other math-related topics—and into his hands-on work as an assembly puzzle enthusiast. Collaborating with fellow puzzle maker Oskar van Deventer, he has created gear-based contraptions such as Gear Shift and a multiple Rubik's Cube variant called Bram's Fortress, several of which are available for 3-D printing through Shapeways. His other pastimes include original origami and juggling up to five balls. Cohen has said that he has Asperger syndrome based on a self diagnosis. As of 2008, Cohen lived in the San Francisco Bay Area of the United States, with his wife Jenna and their three children. The couple divorced in 2022.