The Alphabetum Kaldeorum ("alphabet of the Chaldeans") is one of the best known ciphers of the Middle Ages. Its name refers to Chaldea, whose inhabitants during the medieval era were reputed to have mysterious and magical knowledge.
It can be found in a complete version, together with other non-Latin alphabets, in a manuscript from the year 1428, now in the library at the University of Munich (Cod. 4º 810, fol. 41v). However, its origins lie clearly in an earlier time, as some examples of its practical use demonstrate.
The decipherment of the epitaph accompanying the cenotaph, or symbolic tomb, of Duke Rudolph IV in the Stephansdom in Vienna.
The Alphabetum Kaldeorum was meant primarily for the encipherment of diplomatic correspondence; its alphabet implies that predominantly Latin texts were coded: u and v are equated; w was to be written as double v; j is missing. For frequently arising letters the Alphabetum Kaldeorum provides several different versions, which were used at random so that a decipherment attempt using the classical frequency analysis method should fail. "Nulla", cipher-letters with no plaintext assignment which were to be ignored, were also often added to the enciphered texts to further render frequency-analysis useless.
A possible author of the Alphabetum Kaldeorum is Duke Rudolf IV of Austria (1339–1365), who attributed an Indian origin to them; the letters of the Alphabetum Kaldeorum are probably not, however, at all related to any writing common in India, and are actually independent creations.
Even Rudolf's gravestone in the Stephansdom in Vienna carries an inscription enciphered using the Alphabetum Kaldeorum, which gives the names and titles of the duke.
In cryptography, a cipher is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. To encipher or encode is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "code", as they are both a set of steps that encrypt a message; however, the concepts are distinct in cryptography, especially classical cryptography.
Cryptanalysis refers to the process of analyzing information systems in order to understand hidden aspects of the systems. Cryptanalysis is used to breach cryptographic security systems and gain access to the contents of encrypted messages, even if the cryptographic key is unknown.
The Voynich manuscript is an illustrated codex, hand-written in an unknown script referred to as 'Voynichese.' The vellum on which it is written has been carbon-dated to the early 15th century (1404–1438). Stylistic analysis has indicated the manuscript may have been composed in Italy during the Italian Renaissance. While the origins, authorship, and purpose of the manuscript are still debated, hypotheses range from a script for a natural language or constructed language, an unread code, cypher, or other form of cryptography, or perhaps a hoax, reference work, or work of fiction currently lacking the translation(s) and context needed to both properly entertain or eliminate any of these possibilities.
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, pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing the inverse substitution process to extract the original message.
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 the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence.
In the history of cryptography, the "System 97 Typewriter for European Characters" or "Type B Cipher Machine", codenamed Purple by the United States, was an encryption machine used by the Japanese Foreign Office from February 1939 to the end of World War II. The machine was an electromechanical device that used stepping-switches to encrypt the most sensitive diplomatic traffic. All messages were written in the 26-letter English alphabet, which was commonly used for telegraphy. Any Japanese text had to be transliterated or coded. The 26-letters were separated using a plug board into two groups, of six and twenty letters respectively. The letters in the sixes group were scrambled using a 6 × 25 substitution table, while letters in the twenties group were more thoroughly scrambled using three successive 20 × 25 substitution tables.
The Vigenère cipher is a method of 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.
A polyalphabetic cipher is a substitution, using multiple substitution alphabets. The Vigenère cipher is probably the best-known example of a polyalphabetic cipher, though it is a simplified special case. The Enigma machine is more complex but is still fundamentally a polyalphabetic substitution cipher.
In cryptography, coincidence counting is the technique of putting two texts side-by-side and counting the number of times that identical letters appear in the same position in both texts. This count, either as a ratio of the total or normalized by dividing by the expected count for a random source model, is known as the index of coincidence, or IC for short.
In cryptanalysis, frequency analysis is the study of the frequency of letters or groups of letters in a ciphertext. The method is used as an aid to breaking classical ciphers.
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 in the 1920s–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.
A straddling checkerboard is a device for converting an alphanumeric plaintext into digits whilst simultaneously achieving fractionation and data compression relative to other schemes using digits. It also is known as a monôme-binôme 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 called ADFGX which was first used on 1 March 1918 on the German Western Front. ADFGVX was applied from 1 June 1918 on both the Western Front and Eastern Front.
In cryptanalysis, Kasiski examination is a method of attacking polyalphabetic substitution ciphers, such as the Vigenère cipher. It was first published by Friedrich Kasiski in 1863, but seems to have been independently discovered by Charles Babbage as early as 1846.
Letter frequency is the number of times letters of the alphabet appear on average in written language. Letter frequency analysis dates back to the Arab mathematician Al-Kindi, who formally developed the method to break ciphers. Letter frequency analysis gained importance in Europe with the development of movable type in 1450 AD, where one must estimate the amount of type required for each letterform. Linguists use letter frequency analysis as a rudimentary technique for language identification, where it is particularly effective as an indication of whether an unknown writing system is alphabetic, syllabic, or ideographic.
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 De componendis cifris he explained how his conversation with the papal secretary Leonardo Dati about a recently developed movable type printing press led to the development of his cipher wheel.
Giovan Battista Bellaso was an Italian cryptologist.
A musical cryptogram is a cryptogrammatic sequence of musical symbols which can be taken to refer to an extra-musical text by some 'logical' relationship, usually between note names and letters. The most common and best known examples result from composers using musically translated versions of their own or their friends' names as themes or motifs in their compositions. These are not really rigorous cipher algorithms in the formal sense, but more like musical monograms. The methods used historically by composers were either too incomplete or too simplistic to meaningfully encrypt long text messages. There is a separate history of music ciphers utilizing music notation to encode messages for reasons of espionage or personal security that involved encryption and/or steganography.
ʻAfīf al-Dīn ʻAlī ibn ʻAdlān al-Mawsilī, born in Mosul, was an Arab cryptologist, linguist and poet who is known for his early contributions to cryptanalysis, to which he dedicated at least two books. He was also involved in literature and poetry, and taught on the Arabic language at the Al-Salihiyya Mosque of Cairo.
General der Nachrichtenaufklärung Training Referat was the training organization within the General der Nachrichtenaufklärung (GDNA), the military signals intelligence agency of the Wehrmacht during World War II. Initially established from May 1941, it continued teaching until September 1944. Until 1942, the work of the Training Referat was not fully exploited and only a small beginners course was taught.
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