32:
440:
340:
225:, and this limited advances in mathematics. In this transition, the word was adopted into Medieval Latin as cifra, and then into Middle French as cifre. This eventually led to the English word cipher (minority spelling cypher). One theory for how the term came to refer to encoding is that the concept of zero was confusing to Europeans, and so the term came to refer to a message or communication that was not easily understood.
397:) which changed the substitution alphabet for every letter. For example, "GOOD DOG" can be encrypted as "PLSX TWF" where "L", "S", and "W" substitute for "O". With even a small amount of known or estimated plaintext, simple polyalphabetic substitution ciphers and letter transposition ciphers designed for pen and paper encryption are easy to crack. It is possible to create a secure pen and paper cipher based on a
89:
1549:
212:). If the algorithm is symmetric, the key must be known to the recipient and sender and to no one else. If the algorithm is an asymmetric one, the enciphering key is different from, but closely related to, the deciphering key. If one key cannot be deduced from the other, the asymmetric key algorithm has the public/private key property and one of the keys may be made public without loss of confidentiality.
409:, several rotor disks provided polyalphabetic substitution, while plug boards provided another substitution. Keys were easily changed by changing the rotor disks and the plugboard wires. Although these encryption methods were more complex than previous schemes and required machines to encrypt and decrypt, other machines such as the British
186:). The encrypting procedure is varied depending on the key, which changes the detailed operation of the algorithm. A key must be selected before using a cipher to encrypt a message. Without knowledge of the key, it should be extremely difficult, if not impossible, to decrypt the resulting ciphertext into readable plaintext.
486:
Computational power available, i.e., the computing power which can be brought to bear on the problem. It is important to note that average performance/capacity of a single computer is not the only factor to consider. An adversary can use multiple computers at once, for instance, to increase the speed
154:
Codes generally substitute different length strings of characters in the output, while ciphers generally substitute the same number of characters as are input. A code maps one meaning with another. Words and phrases can be coded as letters or numbers. Codes typically have direct meaning from input to
456:
In a symmetric key algorithm (e.g., DES and AES), the sender and receiver must have a shared key set up in advance and kept secret from all other parties; the sender uses this key for encryption, and the receiver uses the same key for decryption. The design of AES (Advanced
Encryption System) was
375:). For example, "GOOD DOG" can be encrypted as "PLLX XLP" where "L" substitutes for "O", "P" for "G", and "X" for "D" in the message. Transposition of the letters "GOOD DOG" can result in "DGOGDOO". These simple ciphers and examples are easy to crack, even without plaintext-ciphertext pairs.
265:(meaning Chinese characters in Japanese) characters to supplement the native Japanese characters representing syllables. An example using English language with Kanji could be to replace "The quick brown fox jumps over the lazy dog" by "The quick brown 狐 jumps 上 the lazy 犬".
246:
In casual contexts, "code" and "cipher" can typically be used interchangeably; however, the technical usages of the words refer to different concepts. Codes contain meaning; words and phrases are assigned to numbers or symbols, creating a shorter message.
457:
beneficial because it aimed to overcome the flaws in the design of the DES (Data encryption standard). AES's designer's claim that the common means of modern cipher cryptanalytic attacks are ineffective against AES due to its design structure.
351:
is one of the earliest known cryptographic systems. Julius Caesar used a cipher that shifts the letters in the alphabet in place by three and wrapping the remaining letters to the front to write to Marcus
Tullius Cicero in approximately 50 BC.
272:
Ciphers, on the other hand, work at a lower level: the level of individual letters, small groups of letters, or, in modern schemes, individual bits and blocks of bits. Some systems used both codes and ciphers in one system, using
162:
which linked a random string of characters or numbers to a word or phrase. For example, "UQJHSE" could be the code for "Proceed to the following coordinates." When using a cipher the original information is known as
404:
During the early twentieth century, electro-mechanical machines were invented to do encryption and decryption using transposition, polyalphabetic substitution, and a kind of "additive" substitution. In
221:
Originating from the Arabic word for zero صفر (sifr), the word "cipher" spread to Europe as part of the Arabic numeral system during the Middle Ages. The Roman numeral system lacked the concept of
155:
key. Codes primarily function to save time. Ciphers are algorithmic. The given input must follow the cipher's process to be solved. Ciphers are commonly used to encrypt written information.
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1359:
171:. The ciphertext message contains all the information of the plaintext message, but is not in a format readable by a human or computer without the proper mechanism to decrypt it.
232:
was later also used to refer to any Arabic digit, or to calculation using them, so encoding text in the form of Arabic numerals is literally converting the text to "ciphers".
989:
530:
proved, using information theory considerations, that any theoretically unbreakable cipher must have keys which are at least as long as the plaintext, and used only once:
910:. 2005 13th IEEE International Conference on Networks, Jointly held with the 2005 IEEE 7th Malaysia International Conference on Communication. Vol. 2. Kuala Lumpur:
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Another example is given by whole word ciphers, which allow the user to replace an entire word with a symbol or character, much like the way written
Japanese utilizes
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are substantially different from modern methods, and modern ciphers can be classified according to how they operate and whether they use one or two keys.
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Historically, cryptography was split into a dichotomy of codes and ciphers, while coding had its own terminology analogous to that of ciphers: "
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which was used to shorten long telegraph messages which resulted from entering into commercial contracts using exchanges of
147:", as they are both a set of steps that encrypt a message; however, the concepts are distinct in cryptography, especially
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In a pure mathematical attack, (i.e., lacking any other information to help break a cipher) two factors above all count:
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143:. To encipher or encode is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "
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319:. Because of this, codes have fallen into disuse in modern cryptography, and ciphers are the dominant technique.
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139:—a series of well-defined steps that can be followed as a procedure. An alternative, less common term is
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Modern encryption methods can be divided by two criteria: by type of key used, and by type of input data.
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497:, i.e., the size of key used to encrypt a message. As the key size increases, so does the complexity of
615:"Vt hkskdkxt: Early Medieval Cryptography, Textual Errors, and Scribal Agency (Speculum, forthcoming)"
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The operation of a cipher usually depends on a piece of auxiliary information, called a
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There are a variety of different types of encryption. Algorithms used earlier in the
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Since the desired effect is computational difficulty, in theory one would choose an
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Al-Kadi, Ibrahim A. (1992). "Origins of
Cryptology: The Arab Contributions".
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which uses multiple reports to suggest that a symmetrical cipher with 128
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Historical pen and paper ciphers used in the past are sometimes known as
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1010:
The
Ciphers of the Monks: A Forgotten Number-notation of the Middle Ages
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311:
However, codes have a variety of drawbacks, including susceptibility to
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801:
GCHQ: The
Uncensored Story of Britain's Most Secret Intelligence Agency
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to the point where it becomes impractical to crack encryption directly.
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Ciphers can be distinguished into two types by the type of input data:
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and desired difficulty level, thus decide the key length accordingly.
1339:
676:"English Civil War cipher belonging to Cromwell ally goes on display"
614:
382:, developed ciphers to send coded messages to his allies during the
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By whether the same key is used for both encryption and decryption (
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452:), where two different keys are used for encryption and decryption.
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By whether they work on blocks of symbols usually of a fixed size (
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911:
590:
The Muslim Next Door: The Qur'an, the Media, and That Veil Thing
435:), where one same key is used for encryption and decryption, and
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25:
1034:"Cryptology: From Caesar Ciphers to Public-key Cryptosystems"
513:
1121:
Cryptography and
Network Security: Principles and Practices
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sometimes use specific symbols to abbreviate whole words.
222:
189:
Most modern ciphers can be categorized in several ways:
906:
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with 256 bits, all have similar difficulty at present.
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Cryptographically secure pseudorandom number generator
902:
Ho, Yean Li; Samsudin, Azman; Belaton, Bahari (2005).
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for a key (i.e., "brute force" attack) substantially.
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158:
Codes operated by substituting according to a large
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343:
Visual representation of how Caesar's Cipher works.
16:
Algorithm for encrypting and decrypting information
903:
520:, an asymmetric cipher with 3072 bit keys, and an
277:to increase the security. In some cases the terms
1086:Elementary Cryptanalysis: A Mathematical Approach
413:were invented to crack these encryption methods.
467:, which encrypt block of data of fixed size, and
831:Caldwell, William Casey (2022). "Shakespeare's
939:The Codebreakers – The Story of Secret Writing
424:By type of key used ciphers are divided into:
1206:
378:In the 1640s, the Parliamentarian commander,
8:
838:SEL: Studies in English Literature 1500–1900
315:and the difficulty of managing a cumbersome
512:An example of this process can be found at
473:, which encrypt continuous streams of data.
208:), or if a different key is used for each (
1213:
1199:
1191:
1187:
1032:Luciano, Dennis; Prichett, Gordon (1987).
970:: CS1 maint: location missing publisher (
1090:Mathematical Association of America Press
729:"Communication Theory of Secrecy Systems"
197:), or on a continuous stream of symbols (
76:Learn how and when to remove this message
39:This article includes a list of general
592:. White Cloud Press. pp. 240–241.
580:
963:
401:, but these have other disadvantages.
380:Edward Montagu, 2nd Earl of Manchester
7:
103:. Also includes runically unrelated
706:Cryptogtaphy / Theory and Practice
45:it lacks sufficient corresponding
14:
1154:Cryptography: Theory and Practice
1548:
1547:
1152:; Paterson, Maura (2023-01-09).
875:(Corrected ed.). New York:
389:Simple ciphers were replaced by
30:
1039:The College Mathematics Journal
992:from the original on 2024-01-17
1409:Information-theoretic security
1052:10.1080/07468342.1987.11973000
942:(Revised ed.). New York.
613:Saltzman, Benjamin A. (2018).
1:
835:and the Ciphers of History".
588:Ali-Karamali, Sumbul (2008).
99:resembling that found on the
167:, and the encrypted form as
1525:Message authentication code
1480:Cryptographic hash function
1293:Cryptographic hash function
391:polyalphabetic substitution
285:are used synonymously with
1601:
1404:Harvest now, decrypt later
478:Key size and vulnerability
250:An example of this is the
239:
18:
1543:
1520:Post-quantum cryptography
1190:
920:10.1109/ICON.2005.1635595
780:10.1080/0161-119291866801
708:, CRC Press, p. 45,
660:Janeczko, Paul B (2004).
446:asymmetric key algorithms
252:commercial telegraph code
210:asymmetric key algorithms
1510:Quantum key distribution
1500:Authenticated encryption
1355:Random number generation
433:Private-key cryptography
429:symmetric key algorithms
206:symmetric key algorithms
1505:Public-key cryptography
1495:Symmetric-key algorithm
1298:Key derivation function
1258:Cryptographic primitive
1251:Authentication protocol
1241:Outline of cryptography
1236:History of cryptography
1150:Stinson, Douglas Robert
450:Public-key cryptography
329:history of cryptography
60:more precise citations.
21:Cipher (disambiguation)
1246:Cryptographic protocol
796:Aldrich, Richard James
443:
359:. They include simple
344:
149:classical cryptography
112:
1399:End-to-end encryption
1345:Cryptojacking malware
851:10.1353/sel.2022.0003
522:elliptic curve cipher
442:
393:ciphers (such as the
369:transposition ciphers
342:
91:
1515:Quantum cryptography
1439:Trusted timestamping
1015:Franz Steiner Verlag
914:. pp. 710–715.
867:Gaines, Helen Fouché
361:substitution ciphers
178:(or, in traditional
101:Kensington Runestone
19:For other uses, see
1278:Cryptographic nonce
980:"Ciphers vs. codes"
702:Stinson, Douglas R.
559:List of ciphertexts
554:Encryption software
242:Code (cryptography)
1384:Subliminal channel
1368:Pseudorandom noise
1315:Key (cryptography)
1116:Stallings, William
877:Dover Publications
444:
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107:writing style and
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1444:Key-based routing
1434:Trapdoor function
1305:Digital signature
1167:978-1-032-47604-9
1135:978-0-13-670722-6
815:978-0-00-727847-3
499:exhaustive search
489:exhaustive search
384:English Civil War
373:Rail Fence Cipher
357:classical ciphers
275:superencipherment
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1379:Insecure channel
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1156:(6th ed.).
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1013:. Stuttgart:
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313:cryptanalysis
309:
308:" and so on.
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109:pigpen cipher
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1578:Cryptography
1485:Block cipher
1330:Key schedule
1320:Key exchange
1310:Kleptography
1273:Cryptosystem
1222:Cryptography
1153:
1139:. Retrieved
1120:
1088:. New York:
1085:
1071:. Retrieved
1043:
1037:
1009:
994:. Retrieved
985:Khan Academy
983:
938:
923:. Retrieved
905:
871:
842:
836:
832:
800:
771:
765:
743:. Retrieved
736:the original
723:
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684:. Retrieved
679:
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549:Cover-coding
532:one-time pad
526:
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399:one-time pad
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141:encipherment
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117:cryptography
114:
72:
63:
44:
1473:Mathematics
1464:Mix network
1182:Kish cypher
1046:(1): 2–17.
934:Kahn, David
767:Cryptologia
745:February 3,
371:(such as a
105:blackletter
97:rune cipher
58:introducing
1572:Categories
1424:Ciphertext
1394:Decryption
1389:Encryption
1350:Ransomware
1141:2024-06-30
1073:2023-02-19
996:2024-06-30
925:2024-06-30
804:. London:
758:References
662:Top Secret
625:(4): 975.
514:Key Length
335:Historical
169:ciphertext
137:decryption
133:encryption
66:March 2009
41:references
1414:Plaintext
1158:CRC Press
966:cite book
936:(1996) .
869:(1956) .
859:1522-9270
824:503638180
647:165362817
507:algorithm
363:(such as
256:telegrams
228:The term
217:Etymology
165:plaintext
129:algorithm
1553:Category
1459:Kademlia
1419:Codetext
1362:(CSPRNG)
1084:(1968).
1068:14686417
1007:(2001).
990:Archived
958:35159231
895:7634764M
798:(2010).
788:62601575
704:(1995),
686:4 August
680:The Past
639:26584834
619:Speculum
538:See also
495:Key size
395:Vigenère
317:codebook
306:decoding
302:codetext
298:encoding
160:codebook
127:) is an
1583:Ciphers
1229:General
1126:Pearson
1108:149668W
1060:2686311
833:Henry V
283:ciphers
54:improve
1340:Keygen
1164:
1132:
1106:
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417:Modern
367:) and
230:cipher
125:cypher
121:cipher
43:, but
1370:(PRN)
1064:S2CID
1056:JSTOR
784:S2CID
739:(PDF)
732:(PDF)
643:S2CID
635:JSTOR
575:Notes
411:Bombe
365:ROT13
323:Types
279:codes
263:Kanji
1162:ISBN
1130:ISBN
1094:ISBN
1019:ISBN
972:link
954:OCLC
944:ISBN
912:IEEE
881:ISBN
855:ISSN
820:OCLC
810:ISBN
747:2019
710:ISBN
688:2023
594:ISBN
518:bits
347:The
289:and
281:and
223:zero
145:code
123:(or
119:, a
1048:doi
916:doi
847:doi
776:doi
627:doi
487:of
180:NSA
176:key
135:or
115:In
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