Bletchley Park is mainly remembered for breaking messages enciphered on the German Enigma cypher machine, but its greatest cryptographic achievement may have been the breaking of the German on-line teleprinter Lorenz cipher ( known at GC & CS as Tunny ).

However, this cipher is not a machine cipher and as such is not readily suitable for telecommunications.

Close-up of the rotors in a Fialka cipher machine

In 1929 the Polish mathematician Marian Rejewski, who would solve the German Enigma cipher machine in December 1932, began studying actuarial statistics at Göttingen.

An Enigma machine is any of a family of related electro-mechanical rotor cipher machines used for the encryption and decryption of secret messages.

* Mercury ( cipher machine ), a British cipher machine from the 1950s

* M4 ( cipher ), a variant of the Enigma machine

Much of the German cipher traffic was encrypted on the Enigma machine.

The exception was the Italian Navy which, early in 1941, started using a version of the Hagelin rotor-based cipher machine called the C-38.

In the Pacific theater, the Japanese cipher machine dubbed " Purple " by the Americans, was used for highest-level Japanese diplomatic traffic.

It produced a polyalphabetic substitution cipher, but unlike the Enigma machines, it was not a rotor machine, being built around electrical stepping switches.

In the film, a World War II German submarine is boarded in 1942 by disguised United States Navy submariners seeking to capture her Enigma cipher machine.

The first capture of a Naval Enigma machine and associated cipher keys from a U-boat were made on May 9, 1941 by HMS Bulldog of Britain's Royal Navy, commanded by Captain Joe Baker-Cresswell.

** A German Lorenz cipher machine operator sends a 4, 000-character message twice, allowing British mathematician Bill Tutte to decipher the machine's coding mechanism.

The Cipher Bureau breaks the German Enigma cipher and overcomes the ever-growing structural and operating complexities of the evolving Enigma machine | Enigma with plugboard, the main German cipher device during World War II.

The Japanese Navy did not cooperate with the Army in cipher machine development, continuing to the war.

In any case, the Japanese Navy had planned to develop their first cipher machine for the following London Naval Treaty.

In 1928, the chief designer Kazuo Tanabe ( 田辺一雄 ) and Navy Commander, Genichiro Kakimoto ( 柿本権一郎 ) developed a prototype of Red, Ō-bun taipuraita-shiki angō-ki ( 欧文タイプライタ暗号機 ) (" Roman-typewriter cipher machine ").

The prototype used the same principle as the Kryha cipher machine, having a plug-board, and was used by the Japanese Navy and Ministry of Foreign Affairs at negotiations for the London Naval Treaty in 1930.

Even if a symmetric cipher is currently unbreakable by exploiting structural weaknesses in its algorithm, it is possible to run through the entire space of keys in what is known as a brute force attack.

Widely used since, it has been criticized by its inventor, as Gibson himself would later describe it as an " evocative and essentially meaningless " buzzword that could serve as a cipher for all of his " cybernetic musings ".

MediaCrypt AG is now offering a successor to IDEA and focuses on its new cipher ( official release on May 2005 ) IDEA NXT, which was previously called FOX.

As noted in " Have His Carcase ", he communicated at that time with British Intelligence using the Playfair cipher and became proficient in its use.

It is derived from the Vernam cipher, named after Gilbert Vernam, one of its inventors.

The Rail Fence cipher is a form of transposition cipher that gets its name from the way in which it is encoded.

For a stream cipher to be secure, its keystream must have a large period and it must be impossible to recover the cipher's key or internal state from the keystream.

In cryptanalysis and computer security, a dictionary attack is a technique for defeating a cipher or authentication mechanism by trying to determine its decryption key or passphrase by searching likely possibilities.

For example, suppose that a bank uses a stream cipher to hide its financial information, and a user sends an encrypted message containing, say, "< tt > TRANSFER $ 0000100. 00 TO ACCOUNT # 199 </ tt >.

The Advanced Encryption Standard ( AES ), the block cipher ratified as a standard by National Institute of Standards and Technology of the United States ( NIST ), was chosen using a process markedly more open and transparent than its predecessor, the aging Data Encryption Standard ( DES ).

In cryptography, RC5 is a block cipher notable for its simplicity.

In 2001, NIST revised its list of approved modes of operation by including AES as a block cipher and adding CTR mode in SP800-38A, Recommendation for Block Cipher Modes of Operation.

Despite its invention by Wheatstone, it became known as the Playfair cipher after Lord Playfair, who heavily promoted its use.

The initial analysis done by the NSA in 1953 did not absolutely conclude that it was a hand cipher, but its placement in a hollowed out 5c coin implied it could be broken by pencil and paper.

The VIC cipher remained unbroken until more information about its structure was available.

Specifically, Michael Luby and Charles Rackoff analyzed the Feistel cipher construction, and proved that if the round function is a cryptographically secure pseudorandom function, with K < sub > i </ sub > used as the seed, then 3 rounds is sufficient to make the block cipher a pseudorandom permutation, while 4 rounds is sufficient to make it a " strong " pseudorandom permutation ( which means that it remains pseudorandom even to an adversary who gets oracle access to its inverse permutation ).

For example, MISTY1 is a Feistel cipher using a three-round Feistel network in its round function, Skipjack is a modified Feistel cipher using a Feistel network in its G permutation, and Threefish ( part of Skein ) is a non-Feistel block cipher that uses a Feistel-like MIX function.

AES is available in many different encryption packages, and is the first publicly accessible and open cipher approved by the National Security Agency ( NSA ) for top secret information when used in an NSA approved cryptographic module ( see Security of AES, below ).

There are many theories about how the word " cipher " may have come to mean " encoding ":

A month later Igor Gouzenko, a cipher clerk in Ottawa, took political asylum in Canada and gave the Royal Canadian Mounted Police many agent names ; Philby could do nothing about this.

Leet may also be considered a substitution cipher, although many dialects or linguistic varieties exist in different online communities.

The Vigenère () cipher has been reinvented many times.

Like many autokey ciphers it used the plaintext to encrypt itself ; however, since there was no additional key, it is no easier for the intended recipient to read the message than anyone else who knows that the cipher is being used.

Polyalphabetic substitution cipher designers seem to have concentrated on obscuring the choice of a few such alphabets ( repeating as needed ), not on the increased security possible by using many and never repeating any.

The ' ultimate ' cipher of this type would be one in which such a ' long ' key could be generated from a simple pattern ( ideally automatically ), producing a cipher in which there are so many substitution alphabets that frequency counting and statistical attacks would be effectively impossible.

* Site with cipher machine images, many of rotor machines

Since Dee is well-known to have been a spy for Elizabeth I's court, there are many modern interpretations of his Angelic manuscripts as cryptographic documents-most likely polyalphabetic ciphers-designed to disguise political messages ( see for instance, Langford This aspect of the manuscripts is not of major concern to Enochian magicians, but there is no doubt that Dee's knowledge of mathematics and sophisticated cipher systems contributed extensively to his magical system.

The notes also include the Pigpen cipher, devised by the Freemasons, and it may not be coincidental that the abbreviation AVM seen in Latin letters on the Kensington stone also appears ( for AUM ) on many Masonic gravestones ; Wolter and Nielsen in their 2005 book even suggested a connection with the Knights Templar.

The MD-MITM has been used for cryptanalysis of among many, the GOST block cipher, where it has been shown that a 3D-MITM has significantly reduced the time complexity for an attack on it.

Also, many hash functions ( including SHA-1 and SHA-2 ) are built by using a special-purpose block cipher in a Davies-Meyer or other construction.

There have been many attempts to break the remaining cipher ( s ).

This means that the cipher can in many cases be identified as a transposition by the close similarity of its letter statistics with the letter frequencies of the underlying language.

Because both ciphers classically employed novels as part of their key material, many sources confuse the book cipher and the running key cipher.

Essentially all ciphers remained vulnerable to the cryptanalytic technique of frequency analysis until the development of the polyalphabetic cipher, and many remained so thereafter.

The vetting process for a new cipher design standard usually takes many years and includes exhaustive testing of large quantities of ciphertext for any statistical departure from random noise.

Nonetheless poor cipher usage or reliance on home-grown proprietary algorithms that have not been subject to thorough scrutiny has resulted in many computer-age encryption systems that are still subject to ciphertext-only attack.

* In an effort to avoid simple relationships between the cipher key and the subkeys, to resist such forms of cryptanalysis as related-key attacks and slide attacks, many modern ciphers use much more elaborate key schedules, algorithms that use a one-way function to generate an " expanded key " from which subkeys are drawn.

A cipher is a means of concealing a message, where letters of the message are substituted or transposed for other letters, letter pairs, and sometimes for many letters.

Here the cipher is one of many hidden messages tucked away in paintings and photos of historic events or people.