In cryptography , a rotor machine is an electro-mechanical stream cipher device used for encrypting and decrypting messages. Rotor machines were the cryptographic state-of-the-art for much of the 20th century; they were in widespread use from the 1920s to the 1970s. The most famous example is the German Enigma machine , the output of which was deciphered by the Allies during World War II, producing intelligence code-named Ultra .
81-529: The Lorenz SZ40 , SZ42a and SZ42b were German rotor stream cipher machines used by the German Army during World War II . They were developed by C. Lorenz AG in Berlin . The model name SZ was derived from Schlüssel-Zusatz , meaning cipher attachment . The instruments implemented a Vernam stream cipher . British cryptanalysts , who referred to encrypted German teleprinter traffic as Fish , dubbed
162-465: A depth , the veteran cryptanalyst Brigadier John Tiltman in the Research Section teased out the two plaintexts and hence the keystream . But even almost 4,000 characters of key was not enough for the team to figure out how the stream was being generated; it was just too complex and seemingly random. After three months, the Research Section handed the task to mathematician Bill Tutte . He applied
243-399: A plaintext letter in the cipher: if this is not the case, deciphering the message is more difficult. For many years, cryptographers attempted to hide the telltale frequencies by using several different substitutions for common letters, but this technique was unable to fully hide patterns in the substitutions for plaintext letters. Such schemes were being widely broken by the 16th century. In
324-497: A "depth", which could be utilised by a cryptanalyst. As was normal telegraphy practice, messages of any length were keyed into a teleprinter with a paper tape perforator. The typical sequence of operations would be that the sending operator would punch up the message, make contact with the receiving operator, use the EIN / AUS switch on the SZ machine to connect it into the circuit, and then run
405-565: 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. Enigma, and the rotor machines generally, were just what was needed since they were seriously polyalphabetic, using a different substitution alphabet for each letter of plaintext, and automatic, requiring no extraordinary abilities from their users. Their messages were, generally, much harder to break than any previous ciphers. It
486-459: A different substitution for every letter, but this usually meant a very long key, which was a problem in several ways. A long key takes longer to convey (securely) to the parties who need it, and so mistakes are more likely in key distribution. Also, many users do not have the patience to carry out lengthy, letter-perfect evolutions, and certainly not under time pressure or battlefield stress. The 'ultimate' cipher of this type would be one in which such
567-427: A fresh new secret key for each session/conversation (forward secrecy). When used with asymmetric ciphers for key transfer, pseudorandom key generators are nearly always used to generate the symmetric cipher session keys. However, lack of randomness in those generators or in their initialization vectors is disastrous and has led to cryptanalytic breaks in the past. Therefore, it is essential that an implementation use
648-615: A garden shed in Southend-on-Sea . It was found to be the World War II military version, was refurbished and in May 2016 installed next to the SZ42 machine in the museum's "Tunny" gallery. Rotor machine The primary component of a rotor machine is a set of rotors , also termed wheels or drums , which are rotating disks with an array of electrical contacts on either side. The wiring between
729-463: A handful of different alphabets could be used; anything more complex would be impractical. However, using only a few alphabets left the ciphers vulnerable to attack. The invention of rotor machines mechanised polyalphabetic encryption, providing a practical way to use a much larger number of alphabets. The earliest cryptanalytic technique was frequency analysis , in which letter patterns unique to every language could be used to discover information about
810-691: A machine that could be attached to any teleprinter. The first machine was referred to as the SZ40 (old type) which had ten rotors with fixed cams. It was recognised that the security of this machine was not great. The definitive SZ40 had twelve rotors with movable cams. The rightmost five rotors were called Spaltencäsar but named the Chi wheels by Bill Tutte . The leftmost five were named Springcäsar , Psi wheels to Tutte. The middle two Vorgeleger rotors were called Mu or motor wheels by Tutte. The five data bits of each ITA2 -coded telegraph character were processed first by
891-425: A message does not guarantee that it will remain unchanged while encrypted. Hence, often a message authentication code is added to a ciphertext to ensure that changes to the ciphertext will be noted by the receiver. Message authentication codes can be constructed from an AEAD cipher (e.g. AES-GCM ). However, symmetric ciphers cannot be used for non-repudiation purposes except by involving additional parties. See
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#1732905261118972-407: A message of some 4,000 characters was transmitted from Athens to Vienna . However, the message was not received correctly at the other end. The receiving operator then sent an uncoded request back to the sender asking for the message to be retransmitted. This let the codebreakers know what was happening. The sender then retransmitted the message but, critically, did not change the key settings from
1053-486: A message to have the same secret key. All early cryptographic systems required either the sender or the recipient to somehow receive a copy of that secret key over a physically secure channel. Nearly all modern cryptographic systems still use symmetric-key algorithms internally to encrypt the bulk of the messages, but they eliminate the need for a physically secure channel by using Diffie–Hellman key exchange or some other public-key protocol to securely come to agreement on
1134-614: A number of bits and encrypt them in a single unit, padding the plaintext to achieve a multiple of the block size. The Advanced Encryption Standard (AES) algorithm, approved by NIST in December 2001, uses 128-bit blocks. Examples of popular symmetric-key algorithms include Twofish , Serpent , AES (Rijndael), Camellia , Salsa20 , ChaCha20 , Blowfish , CAST5 , Kuznyechik , RC4 , DES , 3DES , Skipjack , Safer , and IDEA . Symmetric ciphers are commonly used to achieve other cryptographic primitives than just encryption. Encrypting
1215-408: A raised (active) or lowered (inactive) position. In the raised position they generated a '1' which reversed the value of a bit, in the lowered position they generated a '0' which left the bit unchanged. The number of cams on each wheel equalled the number of impulses needed to cause them to complete a full rotation. These numbers are all co-prime with each other, giving the longest possible time before
1296-418: A reciprocal cipher, a mathematical involution on each typed-in letter. Instead of designing two kinds of machines, one for encrypting and one for decrypting, all the machines can be identical and can be set up (keyed) the same way. Examples of reciprocal ciphers include: The majority of all modern ciphers can be classified as either a stream cipher , most of which use a reciprocal XOR cipher combiner, or
1377-405: A source of high entropy for its initialization. A reciprocal cipher is a cipher where, just as one enters the plaintext into the cryptography system to get the ciphertext , one could enter the ciphertext into the same place in the system to get the plaintext. A reciprocal cipher is also sometimes referred as self-reciprocal cipher . Practically all mechanical cipher machines implement
1458-512: A standard Lorenz teleprinter. It had a metal base 19 in × 15.5 in (48 cm × 39 cm) and was 17 in (43 cm) high. The teleprinter characters consisted of five data bits (or "impulses"), encoded in the International Telegraphy Alphabet No. 2 (ITA2) . The machine generated a stream of pseudorandom characters. These formed the key that was combined with the plaintext input characters to form
1539-488: A technique that he had been taught in his cryptographic training, of writing out the key by hand and looking for repetitions. Tutte did this with the original teleprinter 5-bit International Telegraph Alphabet No. 2 (ITA2) (which was a development of the Baudot code (ITA1) ), which led him to his initial breakthrough of recognising a 41-bit repetition. Over the following two months up to January 1942, Tutte and colleagues worked out
1620-451: A transmitting and a receiving teleprinter at each end. For enciphering and deciphering to work, the transmitting and receiving machines had to be set up identically. There were two components to this; setting the patterns of cams on the wheels and rotating the wheels for the start of enciphering a message. The cam settings were changed less frequently before summer 1944. The ψ wheel cams were initially only changed quarterly, but later monthly,
1701-517: Is inspired by Enigma, but makes use of 40-point rotors, allowing letters, numbers and some punctuation; each rotor contains 509 parts. A software implementation of a rotor machine was used in the crypt command that was part of early UNIX operating systems. It was among the first software programs to run afoul of U.S. export regulations which classified cryptographic implementations as munitions. Symmetric-key algorithm Symmetric-key algorithms are algorithms for cryptography that use
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#17329052611181782-418: Is one of the main drawbacks of symmetric -key encryption, in comparison to public-key encryption (also known as asymmetric-key encryption). However, symmetric-key encryption algorithms are usually better for bulk encryption. With exception of the one-time pad they have a smaller key size, which means less storage space and faster transmission. Due to this, asymmetric-key encryption is often used to exchange
1863-417: Is straightforward to create a machine for performing simple substitution. In an electrical system with 26 switches attached to 26 light bulbs, any one of the switches will illuminate one of the bulbs. If each switch is operated by a key on a typewriter , and the bulbs are labelled with letters, then such a system can be used for encryption by choosing the wiring between the keys and the bulb: for example, typing
1944-790: The Battle of the Atlantic . During World War II (WWII), both the Germans and Allies developed additional rotor machines. The Germans used the Lorenz SZ 40/42 and Siemens and Halske T52 machines to encipher teleprinter traffic which used the Baudot code ; this traffic was known as Fish to the Allies. The Allies developed the Typex (British) and the SIGABA (American). During the War
2025-797: The Deutsches Museum , a museum of science and technology in Munich. Two further Lorenz machines are displayed at both Bletchley Park and The National Museum of Computing in the United Kingdom. Another example is on display at the National Cryptologic Museum in Maryland, the United States. John Whetter and John Pether, volunteers with The National Museum of Computing, bought a Lorenz teleprinter on eBay for £9.50 that had been retrieved from
2106-679: The German Army began to use a different variant around 1928. The Enigma (in several variants) was the rotor machine that Scherbius's company and its successor, Heimsoth & Reinke, supplied to the German military and to such agencies as the Nazi party security organization, the SD . The Poles broke the German Army Enigma beginning in December 1932, not long after it had been put into service. On July 25, 1939, just five weeks before Hitler's invasion of Poland,
2187-636: The ISO/IEC 13888-2 standard . Another application is to build hash functions from block ciphers. See one-way compression function for descriptions of several such methods. Many modern block ciphers are based on a construction proposed by Horst Feistel . Feistel's construction makes it possible to build invertible functions from other functions that are themselves not invertible. Symmetric ciphers have historically been susceptible to known-plaintext attacks , chosen-plaintext attacks , differential cryptanalysis and linear cryptanalysis . Careful construction of
2268-523: The Latin alphabet ) before the key repeats, and yet it still only requires you to communicate a key of two letters/numbers to set things up. If a key of 676 length is not long enough, another rotor can be added, resulting in a period 17,576 letters long. In order to be as easy to decipher as encipher, some rotor machines, most notably the Enigma machine , embodied a symmetric-key algorithm , i.e., encrypting twice with
2349-829: The Polish General Staff 's Cipher Bureau shared its Enigma-decryption methods and equipment with the French and British as the Poles' contribution to the common defense against Nazi Germany. Dilly Knox had already broken Spanish Nationalist messages on a commercial Enigma machine in 1937 during the Spanish Civil War . A few months later, using the Polish techniques, the British began reading Enigma ciphers in collaboration with Polish Cipher Bureau cryptologists who had escaped Poland, overrun by
2430-595: The Swiss began development on an Enigma improvement which became the NEMA machine which was put into service after World War II. There was even a Japanese developed variant of the Enigma in which the rotors sat horizontally; it was apparently never put into service. The Japanese PURPLE machine was not a rotor machine, being built around electrical stepping switches , but was conceptually similar. Rotor machines continued to be used even in
2511-502: The US Army 's SIS promptly demonstrated a flaw in the system that allowed the ciphers from it, and from any machine with similar design features, to be cracked with enough work. Another early rotor machine inventor was Dutchman Hugo Koch , who filed a patent on a rotor machine in 1919. At about the same time in Sweden , Arvid Gerhard Damm invented and patented another rotor design. However,
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2592-399: The ciphertext , which provide clues about the length of the key. Once this is known, the message essentially becomes a series of messages, each as long as the length of the key, to which normal frequency analysis can be applied. Charles Babbage , Friedrich Kasiski , and William F. Friedman are among those who did most to develop these techniques. Cipher designers tried to get users to use
2673-422: The χ wheels were changed monthly but the motor wheel patterns were changed daily. From 1 August 1944, all wheel patterns were changed daily. Initially the wheel settings for a message were sent to the receiving end by means of a 12-letter indicator sent un-enciphered, the letters being associated with wheel positions in a book. In October 1942, this was changed to the use of a book of single-use settings in what
2754-523: The 1920s four men in different countries invented rotor cipher machines to produce a key stream to act instead of a tape. The 1940 Lorenz SZ40/42 was one of these. The logical functioning of the Tunny system was worked out well before the Bletchley Park cryptanalysts saw one of the machines—which only happened in 1945, as Germany was surrendering to the Allies. The SZ machine served as an in-line attachment to
2835-471: The 1920s. He sold a small number of machines to the US Navy in 1931. In Hebern's machines the rotors could be opened up and the wiring changed in a few minutes, so a single mass-produced system could be sold to a number of users who would then produce their own rotor keying. Decryption consisted of taking out the rotor(s) and turning them around to reverse the circuitry. Unknown to Hebern, William F. Friedman of
2916-564: The Enigma .) Scherbius joined forces with a mechanical engineer named Ritter and formed Chiffriermaschinen AG in Berlin before demonstrating Enigma to the public in Bern in 1923, and then in 1924 at the World Postal Congress in Stockholm . In 1927 Scherbius bought Koch's patents, and in 1928 they added a plugboard , essentially a non-rotating manually rewireable fourth rotor, on the front of
2997-498: The Germans, to reach Paris . The Poles continued breaking German Army Enigma—along with Luftwaffe Enigma traffic—until work at Station PC Bruno in France was shut down by the German invasion of May–June 1940. The British continued breaking Enigma and, assisted eventually by the United States, extended the work to German Naval Enigma traffic (which the Poles had been reading before the war), most especially to and from U-boats during
3078-517: The Robinsons, so speeding up the process of finding the Lorenz χ pin wheel settings. Since Colossus generated the putative keys electronically, it only had to read one tape. It did so with an optical reader which, at 5,000 characters per second, was driven much faster than the Robinsons' and meant that the tape travelled at almost 30 miles per hour (48 km/h). This, and the clocking of the electronics from
3159-706: The SZ42B in June 1944. Radioteletype (RTTY) rather than land-line circuits was used for this traffic. These audio frequency shift keying non- Morse (NoMo) messages were picked up by Britain's Y-stations at Knockholt in Kent, its outstation at Higher Wincombe in Wiltshire, and at Denmark Hill in south London, and forwarded to the Government Code and Cypher School at Bletchley Park (BP). Some were deciphered using hand methods before
3240-515: The ciphertext output characters. The combination was by means of the XOR (or modulo 2 addition) process. The key stream consisted of two component parts that were XOR-ed together. These were generated by two sets of five wheels which rotated together. The Bletchley Park cryptanalyst Bill Tutte called these the χ (" chi ") wheels, and the ψ (" psi ") wheels. Each wheel had a series of cams (or "pins") around their circumference. These cams could be set in
3321-449: The complete logical structure of the cipher machine. This remarkable piece of reverse engineering was later described as "one of the greatest intellectual feats of World War II". After this cracking of Tunny, a special team of code breakers was set up under Ralph Tester , most initially transferred from Alan Turing 's Hut 8 . The team became known as the Testery . It performed the bulk of
Lorenz cipher - Misplaced Pages Continue
3402-507: The computer age. The KL-7 (ADONIS), an encryption machine with 8 rotors, was widely used by the U.S. and its allies from the 1950s until the 1980s. The last Canadian message encrypted with a KL-7 was sent on June 30, 1983. The Soviet Union and its allies used a 10-rotor machine called Fialka well into the 1970s. A unique rotor machine called the Cryptograph was constructed in 2002 by Netherlands -based Tatjana van Vark. This unusual device
3483-412: The contacts implements a fixed substitution of letters, replacing them in some complex fashion. On its own, this would offer little security; however, before or after encrypting each letter, the rotors advance positions, changing the substitution. By this means, a rotor machine produces a complex polyalphabetic substitution cipher, which changes with every key press. In classical cryptography , one of
3564-496: The course of a single plaintext. The idea is simple and effective, but proved more difficult to use than might have been expected. Many ciphers were only partial implementations of Alberti's, and so were easier to break than they might have been (e.g. the Vigenère cipher ). Not until the 1840s (Babbage) was any technique known which could reliably break any of the polyalphabetic ciphers. His technique also looked for repeating patterns in
3645-482: The earliest encryption methods was the simple substitution cipher , where letters in a message were systematically replaced using some secret scheme. Monoalphabetic substitution ciphers used only a single replacement scheme — sometimes termed an "alphabet"; this could be easily broken, for example, by using frequency analysis . Somewhat more secure were schemes involving multiple alphabets, polyalphabetic ciphers . Because such schemes were implemented by hand, only
3726-409: The essential reciprocity that allows the same machine with the same settings to be used for both encryption and decryption. Vernam's idea was to use conventional telegraphy practice with a paper tape of the plaintext combined with a paper tape of the key. Each key tape would have been unique (a one-time tape ), but generating and distributing such tapes presented considerable practical difficulties. In
3807-454: The five chi wheels and then further processed by the five psi wheels. The cams on the wheels reversed the value of a bit if in the raised position, but left it unchanged if in the lowered position. Gilbert Vernam was an AT&T Bell Labs research engineer who, in 1917, invented a cipher system that used the Boolean "exclusive or" (XOR) function, symbolised by ⊕. This is represented by
3888-437: The following " truth table ", where 1 represents "true" and 0 represents "false". Other names for this function are: Not equal (NEQ), modulo 2 addition (without 'carry') and modulo 2 subtraction (without 'borrow'). Vernam's cipher is a symmetric-key algorithm , i.e. the same key is used both to encipher plaintext to produce the ciphertext and to decipher ciphertext to yield the original plaintext: and: This produces
3969-527: The front-line troops to capture the documents, technology and personnel of the various German signal intelligence organizations before these secrets could be destroyed, looted, or captured by the Soviets. They were called the Target Intelligence Committee : TICOM. From captured German cryptographers Drs Huttenhain and Fricke they learnt of the development of the SZ40 and SZ42 a/b. The design was for
4050-432: The functions for each round can greatly reduce the chances of a successful attack. It is also possible to increase the key length or the rounds in the encryption process to better protect against attack. This, however, tends to increase the processing power and decrease the speed at which the process runs due to the amount of operations the system needs to do. Most modern symmetric-key algorithms appear to be resistant to
4131-428: The keyboard increments the rotor position and get a new substitution, implementing a polyalphabetic substitution cipher. Depending on the size of the rotor, this may, or may not, be more secure than hand ciphers. If the rotor has only 26 positions on it, one for each letter, then all messages will have a (repeating) key 26 letters long. Although the key itself (mostly hidden in the wiring of the rotor) might not be known,
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#17329052611184212-417: The letter A would make the bulb labelled Q light up. However, the wiring is fixed, providing little security. Rotor machines change the interconnecting wiring with each key stroke. The wiring is placed inside a rotor, and then rotated with a gear every time a letter is pressed. So while pressing A the first time might generate a Q , the next time it might generate a J . Every letter pressed on
4293-725: The machine and its traffic Tunny (meaning tunafish) and deduced its logical structure three years before they saw such a machine. The SZ machines were in-line attachments to standard teleprinters . An experimental link using SZ40 machines was started in June 1941. The enhanced SZ42 machines were brought into substantial use from mid-1942 onwards for high-level communications between the German High Command in Wünsdorf close to Berlin, and Army Commands throughout occupied Europe. The more advanced SZ42A came into routine use in February 1943 and
4374-638: The machine by January 1942 without ever having seen a Lorenz machine, a feat made possible thanks to mistakes made by German operators. Tunny traffic was known by Y Station operators used to listening to Morse code transmission as "new music". Its interception was originally concentrated at the Foreign Office Y Station operated by the Metropolitan Police at Denmark Hill in Camberwell , London. But due to lack of resources at this time (around 1941), it
4455-429: The machine. After the death of Scherbius in 1929, Willi Korn was in charge of further technical development of Enigma. As with other early rotor machine efforts, Scherbius had limited commercial success. However, the German armed forces, responding in part to revelations that their codes had been broken during World War I, adopted the Enigma to secure their communications. The Reichsmarine adopted Enigma in 1926, and
4536-457: The methods for attacking these types of ciphers don't need that information. So while such a single rotor machine is certainly easy to use, it is no more secure than any other partial polyalphabetic cipher system. But this is easy to correct. Simply stack more rotors next to each other, and gear them together. After the first rotor spins "all the way", make the rotor beside it spin one position. Now you would have to type 26 × 26 = 676 letters (for
4617-501: The mid-15th century, a new technique was invented by Alberti , now known generally as polyalphabetic ciphers , which recognised the virtue of using more than a single substitution alphabet; he also invented a simple technique for "creating" a multitude of substitution patterns for use in a message. Two parties exchanged a small amount of information (referred to as the key ) and used it to create many substitution alphabets, and so many different substitutions for each plaintext letter over
4698-406: The optically read paper tape sprocket holes, completely eliminated the Robinsons' synchronisation problems. Bletchley Park management, which had been sceptical of Flowers's ability to make a workable device, immediately began pressuring him to construct another. After the end of the war, Colossus machines were dismantled on the orders of Winston Churchill, but GCHQ retained two of them. By the end of
4779-447: The original "HQIBPEXEZMUG". This was a forbidden practice; using a different key for every different message is critical to any stream cipher's security. This would not have mattered had the two messages been identical, however the second time the operator made a number of small alterations to the message, such as using abbreviations, making the second message somewhat shorter. From these two related ciphertexts, known to cryptanalysts as
4860-494: The pattern repeated. This is the product of the number of positions of the wheels. For the set of χ wheels it was 41 × 31 × 29 × 26 × 23 = 22,041,682 and for the ψ wheels it was 43 × 47 × 51 × 53 × 59 = 322,303,017. The number of different ways that all twelve wheels could be set was 1.603 × 10 i.e. 16 billion billion. The set of five χ wheels all moved on one position after each character had been enciphered. The five ψ wheels, however, advanced intermittently. Their movement
4941-596: The pin wheel settings were found by the Testery, the Tunny machine was set up and run so that the messages could be printed. A family of machines known as " Robinsons " were built for the Newmanry. These used two paper tapes , along with logic circuitry, to find the settings of the χ pin wheels of the Lorenz machine. The Robinsons had major problems keeping the two paper tapes synchronized and were relatively slow, reading only 2,000 characters per second. The most important machine
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#17329052611185022-541: The plaintext and so were autoclaves . The key stream generated by the SZ machines thus had a χ component and a ψ component. Symbolically, the key that was combined with the plaintext for enciphering and with the ciphertext for deciphering, can be represented as follows. However to indicate that the ψ component often did not change from character to character, the term extended psi was used, symbolised as: Ψ' . So enciphering can be shown symbolically as: and deciphering as: Each "Tunny" link had four SZ machines with
5103-610: The process was partially automated, first with Robinson machines and then with the Colossus computers . The deciphered Lorenz messages made one of the most significant contributions to British Ultra military intelligence and to Allied victory in Europe, due to the high-level strategic nature of the information that was gained from Lorenz decrypts. After the Second World War, a group of British and US cryptanalysts entered Germany with
5184-467: The rotor machine was ultimately made famous by Arthur Scherbius , who filed a rotor machine patent in 1918. Scherbius later went on to design and market the Enigma machine . The most widely known rotor cipher device is the German Enigma machine used during World War II, of which there were a number of variants. The standard Enigma model, Enigma I, used three rotors. At the end of the stack of rotors
5265-401: The same cryptographic keys for both the encryption of plaintext and the decryption of ciphertext . The keys may be identical, or there may be a simple transformation to go between the two keys. The keys, in practice, represent a shared secret between two or more parties that can be used to maintain a private information link. The requirement that both parties have access to the secret key
5346-438: The same settings recovers the original message (see involution ). The concept of a rotor machine occurred to a number of inventors independently at a similar time. In 2003, it emerged that the first inventors were two Dutch naval officers , Theo A. van Hengel (1875–1939) and R. P. C. Spengler (1875–1955) in 1915 (De Leeuw, 2003). Previously, the invention had been ascribed to four inventors working independently and at much
5427-549: The same time: Edward Hebern , Arvid Damm , Hugo Koch and Arthur Scherbius . In the United States Edward Hugh Hebern built a rotor machine using a single rotor in 1917. He became convinced he would get rich selling such a system to the military, the Hebern Rotor Machine , and produced a series of different machines with one to five rotors. His success was limited, however, and he went bankrupt in
5508-400: The secret key for symmetric-key encryption. Symmetric-key encryption can use either stream ciphers or block ciphers . Stream ciphers encrypt the digits (typically bytes ), or letters (in substitution ciphers) of a message one at a time. An example is ChaCha20 . Substitution ciphers are well-known ciphers, but can be easily decrypted using a frequency table . Block ciphers take
5589-598: The subsequent work in breaking Tunny messages, but was aided by machines in the complementary section under Max Newman known as the Newmanry . Several complex machines were built by the British to aid the attack on Tunny. The first was the British Tunny . This machine was designed by Bletchley Park, based on the reverse engineering work done by Tiltman's team in the Testery, to emulate the Lorenz Cipher Machine. When
5670-615: The substitution alphabet(s) in use in a mono-alphabetic substitution cipher . For instance, in English, the plaintext letters E, T, A, O, I, N and S, are usually easy to identify in ciphertext on the basis that since they are very frequent, their corresponding ciphertext letters will also be as frequent. In addition, bigram combinations like NG, ST and others are also very frequent, while others are rare indeed (Q followed by anything other than U for instance). The simplest frequency analysis relies on one ciphertext letter always being substituted for
5751-411: The tape through the reader. At the receiving end, the operator would similarly connect his SZ machine into the circuit and the output would be printed up on a continuous sticky tape. Because this was the practice, the plaintext did not contain the characters for "carriage return", "line feed" or the null (blank tape, 00000) character. British cryptographers at Bletchley Park had deduced the operation of
5832-437: The threat of post-quantum cryptography . Quantum computers would exponentially increase the speed at which these ciphers can be decoded; notably, Grover's algorithm would take the square-root of the time traditionally required for a brute-force attack , although these vulnerabilities can be compensated for by doubling key length. For example, a 128 bit AES cipher would not be secure against such an attack as it would reduce
5913-415: The time required to test all possible iterations from over 10 quintillion years to about six months. By contrast, it would still take a quantum computer the same amount of time to decode a 256 bit AES cipher as it would a conventional computer to decode a 128 bit AES cipher. For this reason, AES-256 is believed to be "quantum resistant". Symmetric-key algorithms require both the sender and the recipient of
5994-411: The twelve-rotor Lorenz SZ42 on-line teleprinter cipher machine. Some influential figures had doubts about his proposed design for the decryption machine, and Flowers proceeded with the project while partly funding it himself. Like the later ENIAC of 1946, Colossus did not have a stored program , and was programmed through plugboards and jumper cables. It was faster, more reliable and more capable than
6075-525: The war, the Testery had grown to nine cryptographers and 24 ATS girls (as the women serving that role were then called), with a total staff of 118, organised in three shifts working round the clock. Lorenz cipher machines were built in small numbers; today only a handful survive in museums. In Germany, examples may be seen at the Heinz Nixdorf MuseumsForum , a computer museum in Paderborn , and
6156-431: Was "reflected" back through the disks before going to the lamps. The advantage of this was that there was nothing that had to be done to the setup in order to decipher a message; the machine was "symmetrical". The Enigma's reflector guaranteed that no letter could be enciphered as itself, so an A could never turn back into an A . This helped Polish and, later, British efforts to break the cipher. ( See Cryptanalysis of
6237-403: Was an additional, non-rotating disk, the "reflector," wired such that the input was connected electrically back out to another contact on the same side and thus was "reflected" back through the three-rotor stack to produce the ciphertext . When current was sent into most other rotor cipher machines, it would travel through the rotors and out the other side to the lamps. In the Enigma, however, it
6318-450: Was controlled by the two μ (" mu ") or "motor" wheels in series. The SZ40 μ 61 motor wheel stepped every time but the μ 37 motor wheel stepped only if the first motor wheel was a '1'. The ψ wheels then stepped only if the second motor wheel was a '1'. The SZ42A and SZ42B models added additional complexity to this mechanism, known at Bletchley Park as Limitations . Two of the four different limitations involved characteristics of
6399-511: Was given a low priority. A new Y Station, Knockholt in Kent , was later constructed specifically to intercept Tunny traffic so that the messages could be efficiently recorded and sent to Bletchley Park. The head of Y station, Harold Kenworthy , moved to head up Knockholt. He was later promoted to head the Foreign Office Research and Development Establishment (F.O.R.D.E). On 30 August 1941,
6480-448: Was known as the QEP book. The last two digits of the QEP book entry were sent for the receiving operator to look up in his copy of the QEP book and set his machine's wheels. Each book contained one hundred or more combinations. Once all the combinations in a QEP book had been used it was replaced by a new one. The message settings should never have been re-used, but on occasion they were, providing
6561-584: Was the Colossus of which ten were in use by the war's end, the first becoming operational in December 1943. Although not fully programmable, they were far more efficient than their predecessors, representing advances in electronic digital computers . The Colossus computers were developed and built by Tommy Flowers , of the Dollis Hill Post Office Research Station , using algorithms developed by Bill Tutte and his team of mathematicians. Colossus proved to be efficient and quick against
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