Adam Back

Adam Back (born July 1970) is a British cryptographer and cypherpunk, and the CEO of Blockstream, a blockchain technology company.

Adam Back is the creator of Hashcash, a proof-of-work system that was used as an early spam control measure on Usenet groups and is also credited with being the first to propose using proof-of-work as a means of combating spam emails. In more recent years, he has been involved with Blockstream, a company that is working on developing technology to support the Bitcoin network.

Adam Back is a computer scientist and entrepreneur who is best known for his work on Bitcoin. He is the CEO of Blockstream, a company that is working to make Bitcoin more accessible and user friendly. Adam is also a co-founder of the Bitcoin Foundation, and he has been involved with Bitcoin since its early days.


Back was born in London, England, in July 1970. His first computer was a Sinclair ZX81. He taught himself Basic, and spent his time reverse engineering video games, finding decryption keys in software packages. He completed his A levels in advanced mathematics, physics and economics.

He has a computer science PhD in distributed systems from the University of Exeter. During his PhD, Back worked with compilers to make use of parallel computers in a semi-automated way. He became interested in pgp encryption, electronic cash and remailers. He spent two thirds of his time working with encryption. After graduation, Adam spent his career as a consultant in start ups and larger companies in applied cryptography, writing cryptographic libraries, designing, reviewing and breaking other people's cryptographic protocols.

Back is a pioneer of early digital asset research similarly as Wei Dai, David Chaum, and Hal Finney. In 1997, Back invented Hashcash. A similar system is used in bitcoin.

He also implemented credlib, a library that implements the credential systems of Stefan Brands and David Chaum.

He was the first to describe the “non-interactive forward secrecy” security property for email and to observe that any identity based encryption scheme can be used to provide non-interactive forward secrecy.

He is also known for promoting the use of ultra-compact code with his 2-line and 3-line RSA in Perl signature file and non-exportable T-shirts to protest cryptography export regulations.

Back was one of the first two people to receive an email from Satoshi Nakamoto. In 2016, the Financial Times cited Back as a potential Nakamoto candidate, along with Nick Szabo and Hal Finney. 

Back has promoted the use of satellites and mesh networks to broadcast and receive bitcoin transactions, as a backup for the traditional internet.

On 3 October 2016, Back was appointed as CEO of Blockstream. Since then he has introduced products such as the Liquid sidechain, Blockstream Mining Notes, mining colocation services, the Jade hardware wallet, and the Core Lightning implementation.


Adam Back envisions a future where digital assets and cryptography play a central role in transforming the way we exchange value and secure our digital transactions. With a background in computer science and a deep understanding of distributed systems, Back has dedicated his career to advancing the field of applied cryptography. His vision encompasses the development and implementation of innovative cryptographic protocols and technologies that enable secure and efficient digital transactions.

Back recognizes the importance of resilience and decentralization in the digital ecosystem. He has championed the use of satellite and mesh networks to enhance the robustness of transmitting and receiving Bitcoin transactions, offering an alternative to traditional internet connectivity. As the CEO of Blockstream, Back continues to drive innovation by introducing products such as the Liquid sidechain, Blockstream Mining Notes, and the Core Lightning implementation, all aimed at further advancing the capabilities and scalability of blockchain technology.

Through his pioneering work, Back envisions a future where digital assets, cryptography, and decentralized systems empower individuals and organizations, providing secure and efficient means of conducting transactions and reshaping the global financial landscape.

Recognition and Awards
One of Back's notable accomplishments is the invention of Hashcash in 1997. This innovative system introduced the concept of proof-of-work, which later became a fundamental component of Bitcoin and other cryptocurrencies. Hashcash provided a practical solution for mitigating email spam and denial-of-service attacks by requiring computational effort to validate and process messages. This pioneering work laid the groundwork for the development of decentralized, secure digital currencies. Back's expertise in cryptography led him to develop and implement various cryptographic protocols. He implemented credlib, a library that incorporated the credential systems of renowned cryptographers Stefan Brands and David Chaum. This implementation contributed to the advancement of secure and privacy-preserving digital credential systems. Furthermore, Back's contributions extend to the exploration of encryption schemes and security properties. He was the first to describe the concept of "non-interactive forward secrecy," a security property crucial for protecting email communications. Back also highlighted the versatility of identity-based encryption schemes in providing non-interactive forward secrecy, expanding the possibilities for secure and private communication channels. Aside from his technical contributions, Back has actively advocated for the accessibility and freedom of cryptography. He famously promoted the use of ultra-compact code, exemplified by his 2-line and 3-line RSA in Perl signature file, demonstrating the efficiency and practicality of cryptographic algorithms. Additionally, he actively protested against cryptography export regulations by creating non-exportable T-shirts, drawing attention to the need for international collaboration and the importance of cryptographic technologies. In recent years, Back's involvement as the CEO of Blockstream has further solidified his impact on the digital asset space. Under his leadership, Blockstream has introduced innovative products such as the Liquid sidechain, offering enhanced scalability and privacy features for blockchain networks. Additionally, he has spearheaded initiatives related to mining colocation services, the Jade hardware wallet, and the Core Lightning implementation, all contributing to the growth and development of blockchain technology.

Adam Back
cryptographer, cypherpunk, technology entrepreneur, security architect
Known for
Blockstream (CEO), Hash cash (proof-of-work algorithm)
Cited (Bitcoin Whitepaper, Satoshi Nakamoto), Liquid sidechain, Blockstream Mining Notes, mining colocation services, the Jade hardware wallet, Core Lightning implementation (developer)
PhD (Computer Science, University of Exeter)
Social Media
Fri Mar 01 2024

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