Adam Back is a cryptographer and one of the original members of the cypherpunk movement. He’s known as the CEO of Blockstream and as the inventor of the Proof of Work protocol Hashcash, which was cited in the Bitcoin whitepaper.
Personal history
Adam Back was born in London, United Kingdom, in 1970. He showed an early interest in computers, teaching himself the basic programming language. He went on to achieve a Ph.D. in computer science with a focus on distributed systems from the University of Exeter.
During his studies, he became interested in the academic disciplines later associated with the cypherpunk movement, including PGP encryption and electronic cash. Following graduation, he worked as a cryptography consultant.
Achievements in cryptography
Adam Back is known as a cypherpunk, one of the cryptographers and computer scientists who worked on early digital asset research in the 1990s and 2000s alongside renowned peers such as Hal Finney, David Chaum, and Satoshi Nakamoto.
In 1997, Back invented a system called Hashcash, which was based on the Proof of Work (PoW) concept that had previously been proposed by Moni Naor and Cynthia Dwork in 1993. In Hashcash, PoW is used to protect against email spam and denial-of-service (DOS) attacks by requiring a minimum amount of computational work to send an email.
Back was also the first to propose a system called “non-interactive forward secrecy” that could be used to secure emails.
Relationship with and candidacy for Satoshi Nakamoto
Adam Back is one of the first people known to have been contacted by the mysterious creator of Bitcoin, Satoshi Nakamoto. He has also been positioned as a potential candidate for Satoshi's real-life identity, although he has strenuously denied this.
In 2008, Satoshi Nakamoto published the Bitcoin whitepaper, which cites Adam Back’s Hashcash as the inspiration for Bitcoin’s Proof of Work system. Over the years, as interest in Satoshi's identity grew, Back disclosed that he had corresponded with the Bitcoin creator via email, but for many years, he declined to publish the emails.
In 2020, a YouTuber released a video alleging that Back is Satoshi, citing the lack of willingness to publish the emails, along with analysis of posting behaviors on the Bitcointalk forum as circumstantial evidence. The video came amid the controversy surrounding the Bitcoin block size wars, in which Back had been involved, advocating against the Bitcoin Cash hard fork.
Also in 2020, Australian computer scientist Craig Wright dropped a lawsuit against Back. Wright brought the lawsuit after Back refuted Wright’s claim to the identity of Satoshi Nakamoto. In 2024, a UK court ruled that Wright was in contempt of court for his persistent and false attempts to claim the identity of Satoshi.
As part of the legal case against Wright, Back released the 2008 emails between himself and Satoshi Nakamoto for the first time. In the emails, Back and Satoshi discuss the Bitcoin whitepaper, and Back refers Satoshi to the work of Wei Dei, another prominent cryptographer, and cypherpunk. The sequence of five emails ends on January 10, 2009, when Satoshi informs Back that Bitcoin has been launched.
Unfortunately, the emails leave no clues as to the true identity of Satoshi Nakamoto, although their publication appears to cement Back’s claim that he is not Satoshi.
Blockstream
Adam Back is the founder and CEO of Blockstream, a blockchain development company focused on building solutions based on the Bitcoin infrastructure. Blockstream was founded in Canada in 2014 and gained early backing from high-profile investors, including Reid Hoffman, the founder of LinkedIn. During a Series B funding round in 2021, Blockstream was valued at $3.2 billion.
The company’s flagship development is the Liquid Network, which was prototyped in 2015 and officially launched in 2018. The Liquid Network is a Layer 2 Bitcoin sidechain that enables enhanced functionality, including fast, confidential transactions. It supports several applications, and Blockstream offers the protocol to be deployed as a standalone federated sidechain solution.
Blockstream also provides several other services relating to Bitcoin. These include mining co-location services, enabling companies to house their mining equipment in Blockstream’s data centers, and a system that allows the receipt of BTC payments via satellite.
Adam Back essentials
- Adam Back is a cryptographer and one of the original cypherpunks,
- He is known for inventing Hashcash, the first iteration of proof of work, and for being the CEO of Blockstream, a firm offering blockchain development services focused on Bitcoin.
- Back had an early exchange of emails with Satoshi Nakamoto and has been proposed as a candidate for Satoshi; however, the publication of the emails in 2024 appears to prove otherwise.