Cryptography Reference
In-Depth Information
The Secret Development of PKC
Now that we have learned about the pioneering efforts of DiQe, Hellman, and
Merkle in establishing PKC, it is time to remind ourselves that there is always
activity behind the shroud of government agencies involved in cryptology. It
is now
public
knowledge that the notion of PKC had already been discovered
years earlier by British cryptographers, but not
o
E
cially
released until relatively
recently. In December of 1997, five papers, [58], [76], [77], [281], [292], were
released by the Communications-Electronics Security Group (CESG), which is
the technical authority on oQcial cryptographic applications for the British
Government Communications Headquarters (GCHQ), whose duty is to ensure
information security for their government.
Public-key methodologies were first discovered by the CESG in the early
1970s. We begin by talking about the author of two of the aforementioned
papers, who may be seen as the prime motivator. James H. Ellis (1924-1997)
was born in Australia, but his parents returned to London when he was still a
baby. After graduating from the University of London, he was employed at the
Post OQce Research Station at Dollis Hill, whose cryptography section moved to
join the (newly formed) CESG in GCHQ in 1965. There Ellis became a leading
figure in British cryptography. The British government asked Ellis to investigate
the key-distribution problem since management of large amounts of key material
needed for secure communication was problematic for the military. In January
of 1970, Ellis established the fundamental ideas behind public-key cryptography
in [76]. He called his method
nonsecret encryption
(NSE). Hence, the discovery
of the idea of public-key cryptography predated DiQe, Hellman, and Merkle by
more than a half dozen years. In [77], published (internally) in CESG in 1987,
Ellis describes the history of NSE. In this paper, he says: “The task of writing
this paper has devolved to me because NSE was my idea and I can therefore
describe their developments from personal experience.” Also, in this paper Ellis
cites the 1944 publication [282] (by an unknown author for Bell Laboratories),
which he describes as an ingenious idea for secure conversation over a telephone.
This was his inspiration for NSE. Ellis states, in the aforementioned paper, that
this is how the idea was born, that secure communication was possible if the
recipient took part in the encryption process. At the end of his paper Ellis
concludes that the DiQe-Hellman idea “was the start of public awareness on
this type of cryptography and subsequent rediscovery of the NSE techniques I
have described.” Shortly after his death in 1997, GCHQ/CESG released the five
publications cited above. According to a spokesman for the British government,
the release of the papers was a “pan-governmental drive for openness” by their
Labour party.
Another author of one of the aforementioned papers is the second on the
scene. Clifford Cocks joined CESG in September of 1973, where he became
acquainted with Ellis's ideas for NSE. He naturally moved to the idea of a one-
way function since he had studied number theory at the University of Cambridge
as a student. Cocks claimed that it took him only a half hour to invent the notion
in [58], dated November 20, 1973, wherein he essentially describes what we now
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