Editing GCHQ (section)

===CESG===
In October 1969, CESD was merged into GCHQ and becoming '''Communications-Electronic Security Group''' ('''CESG''').<ref name="natarchhistory"/>

In 1977 CESG relocated from Eastcote to Cheltenham.<ref name="natarchhistory"/>

CESG continued as the UK National Technical Authority for [[information assurance]], including [[cryptography]]. CESG did not manufacture security equipment, but worked with industry to ensure the availability of suitable products and services, while GCHQ itself funded research into such areas, for example to the [[Centre for Quantum Computation]] at [[Oxford University]] and the [[Heilbronn Institute for Mathematical Research]] at the [[University of Bristol]].<ref>{{cite web|url=http://www.maths.bristol.ac.uk/research/heilbronn_institute/|title=Heilbronn Institute for Mathematical Research|publisher=[[University of Bristol]]|access-date=30 August 2008|archive-date=22 February 2014|archive-url=https://web.archive.org/web/20140222145451/http://www.maths.bristol.ac.uk/research/heilbronn_institute/|url-status=live}}</ref>

In the 21st century, CESG ran a number of assurance schemes such as CHECK, [[CESG Listed Adviser Scheme|CLAS]], [[Commercial Product Assurance]] (CPA) and CESG Assisted Products Service (CAPS).<ref>{{cite web|url = https://www.cesg.gov.uk/servicecatalogue/Pages/index.aspx|access-date = 17 August 2015|title = CESG Service Catalogue|archive-url = https://web.archive.org/web/20150820011137/http://www.cesg.gov.uk/servicecatalogue/Pages/index.aspx|archive-date = 20 August 2015|url-status = dead}}</ref>

====Public key encryption====
In 1970 the concept for [[public-key encryption]] ([[public key infrastructure]]) was developed and proven by GCHQ's [[James H. Ellis]]. Ellis lacked the [[number theory]] skills required to build a workable system. In 1974 GCHQ mathematician [[Clifford Cocks]] had developed a workable public key cryptography algorithm and a workable PKI system. Cocks's system was not available in the public domain until it was [[declassified]] in 1997.<ref>{{cite web |last=Singh |first=Simon |author-link=Simon Singh |title=Unsung Heroes of Cryptography |url=http://simonsingh.net/media/articles/maths-and-science/unsung-heroes-of-cryptography/ |url-status=live |archive-url=https://web.archive.org/web/20141205012040/http://simonsingh.net/media/articles/maths-and-science/unsung-heroes-of-cryptography/ |archive-date=5 December 2014 |access-date=13 June 2012}} (Originally published in ''[[The Sunday Telegraph]]'')</ref><ref>{{Cite web |title=James Ellis |url=https://www.gchq.gov.uk/person/james-ellis |access-date=2023-11-17 |website=www.gchq.gov.uk |language=en}}</ref>

By 1997 broader public key cryptography commercial technologies had  been independently developed and had become well established, in areas such as [[email security]], [[digital signature]]s, and [[Transport Layer Security|TLS]] (a fundamental [[TCP/IP]] security component) etc.<ref>{{Cite web |title=Introduction to PKI |url=https://www.ncsc.gov.uk/collection/in-house-public-key-infrastructure/introduction-to-public-key-infrastructure |access-date=2023-11-16 |website=www.ncsc.gov.uk |language=en}}</ref> Most notably in 1977 the [[RSA (cryptosystem)|RSA]] algorithm had been developed (equivalent to Cocks's system) and by 1997 was extremely well established.<ref>{{Cite web |title=Prehistory of Public Key Cryptography |url=https://www.cs.columbia.edu/~smb/nsam-160/ |access-date=2023-11-16 |website=www.cs.columbia.edu}}</ref>