Colin Percival

delta compression and the introduction of memory-hard functions, he is also known for developing the Tarsnap

Commonwealth Scholarship to the University of Oxford.^[1]

delta compression algorithm. This new algorithm, called bsdiff, became the new focus of his doctoral research, and later a widely used standard, and his freebsd-update became a part of FreeBSD.^[4] In 2004 he contributed portsnap, which uses bsdiff to distribute snapshots of the FreeBSD ports tree

visiting researcher.^[9] He went on to serve as the FreeBSD Security Officer, from August 2005 to May 2012. He was also elected to the FreeBSD Core Team, for the 2010–2012 term.^[10]

Amazon EC2 platform, and he increased these efforts. Building disk images himself, debugging kernel crashes, and coordinating with people at both Amazon and FreeBSD, he eventually overcame the technical obstacles, and Amazon announced official support for FreeBSD on EC2 in November 2012.^[11] Percival has continued to support FreeBSD on EC2, and in 2019 he was recognized as an AWS Community Hero for his work and enthusiasm.^[12]

REST APIs.^[13] The same year, while working to add passphrase protection to Tarsnap keys, he became dissatisfied with existing key derivation functions. Drawing on his experience in distributed computing, Percival modeled an attacker using specialized hardware to massively parallelize a brute-force search for the passphrase. He concluded that the key derivation functions in use were vulnerable to such an attack, and sought to make these attacks cost-prohibitive by designing an algorithm that must use an amount of memory nearly proportional to its run time. He defined memory-hard functions in these terms, and presented scrypt as a specific example, which he used as the key derivation function for Tarsnap. Memory-hard functions have since become an active area of research in cryptography, and scrypt is used as the basis of proof of work in Litecoin^[14] and some other cryptocurrencies

Type-I diabetes.^[17]