Clifford Cocks | |
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![]() Clifford Cocks at the Royal Society admissions day in London, July 2015 | |
Born | Clifford Christopher Cocks 28 December 1950 [1] Prestbury, Cheshire, England, United Kingdom |
Nationality | British |
Education | Manchester Grammar School |
Alma mater | University of Cambridge (BA) |
Known for | |
Scientific career | |
Fields | Cryptography |
Institutions |
Clifford Christopher Cocks CB FRS [2] (born 28 December 1950) is a British mathematician and cryptographer. In the early 1970s, while working at the United Kingdom Government Communications Headquarters (GCHQ), he developed an early public-key cryptography (PKC) system. This pre-dated commercial offerings, but due to the classified nature of Cocks' work, it did not become widely known until 1997 when the work was declassified.
As his work was not available for public review until 1997, it had no impact on numerous commercial initiatives relating to Internet security that had been commercially developed and that were well established by 1997. His work was technically aligned with the Diffie–Hellman key exchange and elements of the RSA algorithm, these well known systems were independently developed and commercialized. [3] [4]
Cocks was educated at Manchester Grammar School and went on to study the Mathematical Tripos as an undergraduate at King's College, Cambridge. He continued as a PhD student at the University of Oxford, where he specialised in number theory under Bryan Birch, but left academia without finishing his doctorate. [5]
Cocks left Oxford to join Communications-Electronics Security Group (CESG), an arm of GCHQ, in September 1973. Soon after, Nick Patterson told Cocks about James H. Ellis' non-secret encryption, [5] [6] [7] an idea which had been published in 1969 but never successfully implemented. Several people had attempted creating the required one-way functions, but Cocks, with his background in number theory, decided to use prime factorization, [8] and did not even write it down at the time. With this insight, he quickly developed what later became known as the RSA encryption algorithm. [9] [10]
GCHQ was not able to find a way to use the algorithm, and treated it as classified information. The scheme was also passed to the NSA. [8] With a military focus, financial considerations, and low computing power, the power of public-key cryptography was unrealised in both organisations: [5]
I judged it most important for military use. In a fluid military situation you may meet unforeseen threats or opportunities. ... if you can share your key rapidly and electronically, you have a major advantage over your opponent. Only at the end of the evolution from Berners-Lee [in 1989] designing an open internet architecture for CERN, its adaptation and adoption for the Arpanet ... did public key cryptography realise its full potential. -Ralph Benjamin [8]
In 1977, the algorithm was independently invented and published by Rivest, Shamir and Adleman, who named it after their initials. There is no evidence of a hint or leak, conscious or unconscious, and Cocks has dismissed the idea. [8] The British achievement remained secret until 1997. [11]
In 1987, the GCHQ had plans to release the work, but Peter Wright's Spycatcher MI5 memoir caused them to delay revealing the research by ten years. [12] 24 years after its discovery, on 18 December 1997, Cocks revealed the GCHQ history of public-key research in a public talk. James Ellis had died on 25 November 1997, a month before the public announcement was made.
In 2001, Cocks developed one of the first secure identity-based encryption (IBE) schemes, based on assumptions about quadratic residues in composite groups. The Cocks IBE scheme is not widely used in practice due to its high degree of ciphertext expansion. However, it is currently one of the few IBE schemes which do not use bilinear pairings, and rely for security on more well-studied mathematical problems.
In 1968, Cocks won a silver medal at the 10th International Mathematical Olympiad. [13]
Cocks held the post of Chief Mathematician at GCHQ. He established the Heilbronn Institute for Mathematical Research at the University of Bristol. [14]
Cocks was made a Companion of the Order of the Bath in 2008 (the citation describes him as "Counsellor, Foreign and Commonwealth Office"). [15] He was awarded an honorary degree from the University of Bristol in 2008, [16] and an honorary Doctor of Science from the University of Birmingham in 2015. [17]
With James Ellis and Malcolm Williamson, Cocks was honoured for his part in the development of public-key cryptography by the Institute of Electrical and Electronics Engineers (IEEE) [18] in 2010 and by induction into the Cryptologic Hall of Honor in 2021.
Cocks was elected a Fellow of the Royal Society (FRS) in 2015. [19] His certificate of election reads:
Clifford Cocks is distinguished for his work in cryptography. He was the first to devise a practicable implementation of public key cryptography, and more recently a practicable scheme for identity based public key encryption. Such achievements have been fundamental in ensuring the security of the world's electronic communications, security that we now take for granted. [20]
Cryptanalysis refers to the process of analyzing information systems in order to understand hidden aspects of the systems. Cryptanalysis is used to breach cryptographic security systems and gain access to the contents of encrypted messages, even if the cryptographic key is unknown.
In cryptography, key size or key length refers to the number of bits in a key used by a cryptographic algorithm.
Diffie–Hellman (DH) key exchange is a mathematical method of securely exchanging cryptographic keys over a public channel and was one of the first public-key protocols as conceived by Ralph Merkle and named after Whitfield Diffie and Martin Hellman. DH is one of the earliest practical examples of public key exchange implemented within the field of cryptography. Published in 1976 by Diffie and Hellman, this is the earliest publicly known work that proposed the idea of a private key and a corresponding public key.
In cryptography, encryption is the process of transforming information in a way that, ideally, only authorized parties can decode. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Despite its goal, encryption does not itself prevent interference but denies the intelligible content to a would-be interceptor.
Public-key cryptography, or asymmetric cryptography, is the field of cryptographic systems that use pairs of related keys. Each key pair consists of a public key and a corresponding private key. Key pairs are generated with cryptographic algorithms based on mathematical problems termed one-way functions. Security of public-key cryptography depends on keeping the private key secret; the public key can be openly distributed without compromising security.
RSA (Rivest–Shamir–Adleman) is a public-key cryptosystem, one of the oldest widely used for secure data transmission. The initialism "RSA" comes from the surnames of Ron Rivest, Adi Shamir and Leonard Adleman, who publicly described the algorithm in 1977. An equivalent system was developed secretly in 1973 at Government Communications Headquarters (GCHQ), the British signals intelligence agency, by the English mathematician Clifford Cocks. That system was declassified in 1997.
A key in cryptography is a piece of information, usually a string of numbers or letters that are stored in a file, which, when processed through a cryptographic algorithm, can encode or decode cryptographic data. Based on the used method, the key can be different sizes and varieties, but in all cases, the strength of the encryption relies on the security of the key being maintained. A key's security strength is dependent on its algorithm, the size of the key, the generation of the key, and the process of key exchange.
Adi Shamir is an Israeli cryptographer and inventor. He is a co-inventor of the Rivest–Shamir–Adleman (RSA) algorithm, a co-inventor of the Feige–Fiat–Shamir identification scheme, one of the inventors of differential cryptanalysis and has made numerous contributions to the fields of cryptography and computer science.
Articles related to cryptography include:
Identity-based encryption (IBE), is an important primitive of identity-based cryptography. As such it is a type of public-key encryption in which the public key of a user is some unique information about the identity of the user. This means that a sender who has access to the public parameters of the system can encrypt a message using e.g. the text-value of the receiver's name or email address as a key. The receiver obtains its decryption key from a central authority, which needs to be trusted as it generates secret keys for every user.
Cryptography, the use of codes and ciphers to protect secrets, began thousands of years ago. Until recent decades, it has been the story of what might be called classical cryptography — that is, of methods of encryption that use pen and paper, or perhaps simple mechanical aids. In the early 20th century, the invention of complex mechanical and electromechanical machines, such as the Enigma rotor machine, provided more sophisticated and efficient means of encryption; and the subsequent introduction of electronics and computing has allowed elaborate schemes of still greater complexity, most of which are entirely unsuited to pen and paper.
James Henry Ellis was a British engineer and cryptographer. Born in Australia but raised and educated in Britain, Ellis joined GCHQ in 1952. He worked on a number of cryptographic projects, but is credited with some of the original thinking that developed into the field of Public Key Cryptography (PKC).
Malcolm John Williamson was a British mathematician and cryptographer. In 1974 he developed what is now known as Diffie–Hellman key exchange. He was then working at GCHQ and was therefore unable to publicise his research as his work was classified. Martin Hellman, who independently developed the key exchange at the same time, received credit for the discovery until Williamson's research was declassified by the British government in 1997.
Dan Boneh is an Israeli–American professor in applied cryptography and computer security at Stanford University.
In cryptography, PKCS #1 is the first of a family of standards called Public-Key Cryptography Standards (PKCS), published by RSA Laboratories. It provides the basic definitions of and recommendations for implementing the RSA algorithm for public-key cryptography. It defines the mathematical properties of public and private keys, primitive operations for encryption and signatures, secure cryptographic schemes, and related ASN.1 syntax representations.
Cryptography, or cryptology, is the practice and study of techniques for secure communication in the presence of adversarial behavior. More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages. Modern cryptography exists at the intersection of the disciplines of mathematics, computer science, information security, electrical engineering, digital signal processing, physics, and others. Core concepts related to information security are also central to cryptography. Practical applications of cryptography include electronic commerce, chip-based payment cards, digital currencies, computer passwords, and military communications.
The following outline is provided as an overview of and topical guide to cryptography:
Identity-based cryptography is a type of public-key cryptography in which a publicly known string representing an individual or organization is used as a public key. The public string could include an email address, domain name, or a physical IP address.
Bullrun is a clandestine, highly classified program to crack encryption of online communications and data, which is run by the United States National Security Agency (NSA). The British Government Communications Headquarters (GCHQ) has a similar program codenamed Edgehill. According to the Bullrun classification guide published by The Guardian, the program uses multiple methods including computer network exploitation, interdiction, industry relationships, collaboration with other intelligence community entities, and advanced mathematical techniques.