The National Cipher Challenge is an annual

cryptographic Cryptography, or cryptology (from "hidden, secret"; and ''graphein'', "to write", or '' -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adversarial behavior. More gen ...

competition organised by the

University of Southampton The University of Southampton (abbreviated as ''Soton'' in post-nominal letters) is a public university, public research university in Southampton, England. Southampton is a founding member of the Russell Group of research-intensive universit ...

School of Mathematics. Competitors attempt to break

cryptograms A cryptogram is a type of puzzle that consists of a short piece of encryption, encrypted text. Generally the cipher used to encrypt the text is simple enough that the cryptogram can be solved by hand. Substitution ciphers where each letter is ...

published on the competition website. In the 2017, more than 7,500 students took part in the competition. Participants must be in full-time school level education in order to qualify for prizes.

Format

The competition is organised into eight to ten challenges, which are further subdivided into parts A and B. The part A challenge consists of a comparatively simpler cryptogram, and usually provides some useful information to assist in the solving of part B. Part B is usually more complex. In later challenges the cryptograms become harder to break. In the past, part A cryptograms have been encrypted with the

Caesar cipher In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code, or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in t ...

, the

Affine cipher The affine cipher is a type of monoalphabetic substitution cipher, where each letter in an alphabet is mapped to its numeric equivalent, encrypted using a simple mathematical function, and converted back to a letter. The formula used means that ea ...

, the Keyword cipher, the

Transposition cipher In cryptography, a transposition cipher (also known as a permutation cipher) is a method of encryption which scrambles the positions of characters (''transposition'') without changing the characters themselves. Transposition ciphers reorder units ...

, the

Vigenère cipher The Vigenère cipher () is a method of encryption, encrypting alphabetic text where each letter of the plaintext is encoded with a different Caesar cipher, whose increment is determined by the corresponding letter of another text, the key (crypt ...

and the 2x2

Hill cipher In classical cryptography, the Hill cipher is a polygraphic substitution cipher based on linear algebra. Invented by Lester S. Hill in 1929, it was the first polygraphic cipher in which it was practical (though barely) to operate on more than t ...

. The part B challenges are intended to be harder. These begin with relatively simple

substitution ciphers In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key; the "units" may be single letters (the most common), pairs of letters, tri ...

, including the Bacon cipher and

Polybius square The Polybius square, also known as the Polybius checkerboard, is a device invented by the ancient Greeks Cleoxenus and Democleitus, and made famous by the historian and scholar Polybius. The device is used for fractionating plaintext characters s ...

, before moving on to

transposition cipher In cryptography, a transposition cipher (also known as a permutation cipher) is a method of encryption which scrambles the positions of characters (''transposition'') without changing the characters themselves. Transposition ciphers reorder units ...

Playfair cipher The Playfair cipher or Playfair square or Wheatstone–Playfair cipher is a manual symmetric encryption technique and was the first literal digram substitution cipher. The scheme was invented in 1854 by Charles Wheatstone, but bears the name of ...

s and polyalphabetic ciphers such as the

, the

Autokey cipher An autokey cipher (also known as the autoclave cipher) is a cipher that incorporates the message (the plaintext) into the key. The key is generated from the message in some automated fashion, sometimes by selecting certain letters from the text o ...

and the

Alberti cipher The Alberti cipher, created in 1467 by Italian architect Leon Battista Alberti, was one of the first polyalphabetic ciphers. In the opening pages of his treatise ' he explained how his conversation with the papal secretary Leonardo Dati about a r ...

. In the later stages of the competition, the

ADFGVX cipher In cryptography, the ADFGVX cipher was a manually applied field cipher used by the Imperial German Army during World War I. It was used to transmit messages secretly using wireless telegraphy. ADFGVX was in fact an extension of an earlier cipher c ...

, the Solitaire cipher, the Double Playfair cipher, the

, the

Book cipher A book cipher is a cipher in which each word or letter in the plaintext of a message is replaced by some code that locates it in another text, the key. A simple version of such a cipher would use a specific book as the key, and would replace ea ...

and versions of the

Enigma Enigma may refer to: *Riddle, someone or something that is mysterious or puzzling Biology *ENIGMA, a class of gene in the LIM domain Computing and technology * Enigma (company), a New York–based data-technology startup *Enigma machine, a famil ...

and

Fialka In cryptography, Fialka (M-125) is the name of a Cold War-era Soviet cipher machine. A rotor machine, the device uses 10 rotors, each with 30 contacts along with mechanical pins to control stepping. It also makes use of a punched card mechanism. ...

cipher machines have all been used. The 2009 challenge ended with a Jefferson Disk cipher, the 2012 challenge ended with the ADFGVX Cipher, the 2014 with the

Playfair Cipher The Playfair cipher or Playfair square or Wheatstone–Playfair cipher is a manual symmetric encryption technique and was the first literal digram substitution cipher. The scheme was invented in 1854 by Charles Wheatstone, but bears the name of ...

, and the most recent challenge ended with a sectioned Cadenus transposition.

Prizes

£25 cash prizes are awarded to eight random entrants who submit a correct solution for each part A of the challenge. Leaderboards for the part B challenges are also compiled, based on how accurate solutions are and how quickly the entrant broke the cipher. Prizes are awarded to the top three entrants at the end of the challenge. In the 2009/10 challenge, the sponsors provided several prizes: IBM provided iPod Touches to each member of the team winning the Team Prize, Trinity College provided a cash prize of £700, and GCHQ provided a cash prize of £1000. In previous years prizes such as an IBM Thinkpad laptop have been awarded. After the challenge the winners of the top prizes and other randomly selected entrants are invited to a day held at

Bletchley Park Bletchley Park is an English country house and Bletchley Park estate, estate in Bletchley, Milton Keynes (Buckinghamshire), that became the principal centre of Allies of World War II, Allied World War II cryptography, code-breaking during the S ...

consisting of lectures (with subjects such as the Semantic Web,

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

cryptography and

computer programming Computer programming or coding is the composition of sequences of instructions, called computer program, programs, that computers can follow to perform tasks. It involves designing and implementing algorithms, step-by-step specifications of proc ...

) and the prize-giving ceremony. Current sponsors of the competition include

GCHQ Government Communications Headquarters (GCHQ) is an intelligence and security organisation responsible for providing signals intelligence (SIGINT) and information assurance (IA) to the government and armed forces of the United Kingdom. Primar ...

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

British Computer Society image:Maurice Vincent Wilkes 1980 (3).jpg, Sir Maurice Wilkes served as the first President of BCS in 1957. The British Computer Society (BCS), branded BCS, The Chartered Institute for IT, since 2009, is a professional body and a learned ...

Trinity College, Cambridge Trinity College is a Colleges of the University of Cambridge, constituent college of the University of Cambridge. Founded in 1546 by King Henry VIII, Trinity is one of the largest Cambridge colleges, with the largest financial endowment of any ...

Cambridge University Press Cambridge University Press was the university press of the University of Cambridge. Granted a letters patent by King Henry VIII in 1534, it was the oldest university press in the world. Cambridge University Press merged with Cambridge Assessme ...

Winton Capital Management Winton Group (including Winton Capital Management) is a British investment management firm founded by David Harding. In the United States, Winton Group is registered with the Securities and Exchange Commission as an investment advisor and with th ...

and

EPSRC The Engineering and Physical Sciences Research Council (EPSRC) is a British Research Council that provides government funding for grants to undertake research and postgraduate degrees in engineering and the physical sciences, mainly to univers ...

References

External links

The official challenge website

The website of the 2016/17 challenge
(slightly broken)
The website of the 2015/16 challenge
The websites for the challenges earlier than this are no longer available. {{Mathematics in the United Kingdom Computer security in the United Kingdom Cryptography contests Mathematics education in the United Kingdom Secondary schools in the United Kingdom University of Southampton