296:
Inserting round-dependent constants into the encryption process breaks the symmetry between rounds and thus thwarts the most obvious slide attacks. The technique is a standard feature of most modern block ciphers. However, a poor choice of round constants or unintended interrelations between the
362:
techniques include the use of versions of ciphers with fewer rounds than specified by their designers. Since a single round is usually cryptographically weak, many attacks that fail to work against the full version of ciphers will work on such
284:" is used to define the transformation of part of the data (a distinguishing feature of the Feistel design). This operation corresponds to a full round in traditional descriptions of Feistel ciphers (like
343:
assert that one of the goals of optimizing the cipher is reducing the overall workload, the product of the round complexity and the number of rounds. There are two approaches to address this goal:
367:
variants. The result of such attack provides valuable information about the strength of the algorithm, a typical break of the full cipher starts out as a success against a reduced-round one.
125:
193:
254:
808:
670:
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573:
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265:). Most of the modern ciphers use iterative design with number of rounds usually chosen between 8 and 32 (with 64 and even 80 used in
835:
230:, as for these tools the effort grows exponentially with the number of rounds. However, increasing the number of rounds does not
350:
global optimization optimizes the worst-case behavior of more than one round, allowing the use of less sophisticated components.
46:) multiple times inside the algorithm. Splitting a large algorithmic function into rounds simplifies both implementation and
592:
298:
223:
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constants and other cipher components could still allow slide attacks (e.g., attacking the initial version of the
285:
258:
56:
246:
649:. Lecture Notes in Computer Science. Vol. 10402. Springer International Publishing. pp. 647–678.
599:. Lecture Notes in Computer Science. Vol. 12105. Springer International Publishing. pp. 250–279.
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local optimization improves the worst-case behavior of a single round (two rounds for
Feistel ciphers);
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242:
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560:. Lecture Notes in Computer Science. Vol. 1636. Springer Berlin Heidelberg. pp. 245–259.
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make weak ciphers into strong ones, as some attacks do not depend on the number of rounds.
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For example, encryption using an oversimplified three-round cipher can be written as
47:
754:
430:
316:. A poor choice of round constants in this case might make the cipher vulnerable to
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31:
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640:"Proving Resistance Against Invariant Attacks: How to Choose the Round Constants"
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17:
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764:"On Differential and Linear Cryptanalysis of the RC5 Encryption Algorithm"
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Beierle, Christof; Canteaut, Anne; Leander, Gregor; Rotella, Yann (2017).
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utilize very simple key scheduling: the round keys come from adding the
639:
257:"; Shannon was inspired by mixing transformations used in the field of
526:
Serious
Cryptography: A Practical Introduction to Modern Encryption
591:
Dunkelman, Orr; Keller, Nathan; Lasry, Noam; Shamir, Adi (2020).
222:
Increasing the number of rounds "almost always" protects against
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The Design of
Rijndael: AES - The Advanced Encryption Standard
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are implemented using the same function, parameterized by the
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412:
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397:
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688:
Biryukov, Alex (2005). "Product Cipher, Superencryption".
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goes as far back as 1945, to the then-secret version of
149:
59:
728:"A Self-Study Course in Block-Cipher Cryptanalysis"
593:"New Slide Attacks on Almost Self-similar Ciphers"
187:
119:
773:. Springer Berlin Heidelberg. pp. 171–184.
794:Daemen, Joan; Rijmen, Vincent (9 March 2013).
416:
211:. Parameterization is essential to reduce the
8:
762:Kaliski, Burton S.; Yin, Yiqun Lisa (1995).
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42:is a basic transformation that is repeated (
523:Aumasson, Jean-Philippe (6 November 2017).
714:(Version 2.0 ed.). Redwood City, CA:
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27:Repeated basic operation in a cryptosystem
803:. Springer Science & Business Media.
690:Encyclopedia of Cryptography and Security
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154:
148:
96:
83:
70:
58:
506:
446:
386:
120:{\displaystyle C=R_{3}(R_{2}(R_{1}(P)))}
597:Advances in Cryptology – EUROCRYPT 2020
494:
431:"A Mathematical Theory of Cryptography"
376:
255:Communication Theory of Secrecy Systems
552:Biryukov, Alex; Wagner, David (1999).
429:Shannon, Claude (September 1, 1945).
276:descriptions, notably the one of the
241:using repeated application of simple
7:
647:Advances in Cryptology – CRYPTO 2017
771:Advances in Cryptology – CRYPT0’ 95
529:. No Starch Press. pp. 56–57.
215:of the cipher, which could lead to
705:Robshaw, M.J.B. (August 2, 1995).
320:; ciphers broken this way include
25:
692:. Springer US. pp. 480–481.
188:{\displaystyle R_{1},R_{2},...}
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1:
655:10.1007/978-3-319-63715-0_22
605:10.1007/978-3-030-45721-1_10
299:format-preserving encryption
852:
417:Biryukov & Wagner 1999
747:10.1080/0161-110091888754
698:10.1007/0-387-23483-7_320
836:Cryptographic primitives
779:10.1007/3-540-44750-4_14
566:10.1007/3-540-48519-8_18
558:Fast Software Encryption
402:Daemen & Rijmen 2013
259:dynamical systems theory
247:diffusion and confusion
459:Kaliski & Yin 1995
189:
121:
471:Dunkelman et al. 2020
355:Reduced-round ciphers
245:operations producing
190:
122:
267:cryptographic hashes
228:linear cryptanalysis
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143:. Typically, rounds
57:
483:Beierle et al. 2017
306:lightweight ciphers
274:Feistel-like cipher
185:
117:
810:978-3-662-04722-4
672:978-3-319-63714-3
622:978-3-030-45720-4
575:978-3-540-66226-6
536:978-1-59327-826-7
318:invariant attacks
16:(Redirected from
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802:
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726:(January 2000).
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724:Schneier, Bruce
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197:round constant
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40:round function
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24:
18:Round constant
14:
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3:
2:
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708:Block Ciphers
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507:Schneier 2000
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455:
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447:Biryukov 2005
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436:. p. 97.
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411:
407:
404:, p. 74.
403:
398:
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389:, p. 56.
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387:Aumasson 2017
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365:reduced-round
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360:Cryptanalysis
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251:C. E. Shannon
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217:slide attacks
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201:block ciphers
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48:cryptanalysis
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770:
741:(1): 18–34.
738:
734:
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509:, p. 2.
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495:Robshaw 1995
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332:Optimization
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224:differential
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209:key schedule
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32:cryptography
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735:Cryptologia
301:mode FF3).
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545:1012843116
371:References
282:half-round
280:, a term "
133:ciphertext
787:0302-9743
681:0302-9743
663:1611-3349
631:0302-9743
613:1611-3349
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272:For some
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322:SCREAM
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