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• Substitution-permutation_network abstract "In cryptography, an SP-network, or substitution-permutation network (SPN), is a series of linked mathematical operations used in block cipher algorithms such as AES (Rijndael).Other ciphers that use SPNs are 3-Way, PRESENT, SAFER, SHARK, and Square.Such a network takes a block of the plaintext and the key as inputs, and applies several alternating \"rounds\" or \"layers\" of substitution boxes (S-boxes) and permutation boxes (P-boxes) to produce the ciphertext block. The S-boxes and P-boxes transform (sub-)blocks of input bits into output bits. It is common for these transformations to be operations that are efficient to perform in hardware, such as exclusive or (XOR) and bitwise rotation. The key is introduced in each round, usually in the form of \"round keys\" derived from it. (In some designs, the S-boxes themselves depend on the key.)Decryption is done by simply reversing the process (using the inverses of the S-boxes and P-boxes and applying the round keys in reversed order).An S-box substitutes a small block of bits (the input of the S-box) by another block of bits (the output of the S-box). This substitution should be one-to-one, to ensure invertibility (hence decryption). In particular, the length of the output should be the same as the length of the input (the picture on the right has S-boxes with 4 input and 4 output bits), which is different from S-boxes in general that could also change the length, as in DES (Data Encryption Standard), for example. An S-box is usually not simply a permutation of the bits. Rather, a good S-box will have the property that changing one input bit will change about half of the output bits (or an avalanche effect). It will also have the property that each output bit will depend on every input bit.A P-box is a permutation of all the bits: it takes the outputs of all the S-boxes of one round, permutes the bits, and feeds them into the S-boxes of the next round. A good P-box has the property that the output bits of any S-box are distributed to as many S-box inputs as possible.At each round, the round key (obtained from the key with some simple operations, for instance, using S-boxes and P-boxes) is combined using some group operation, typically XOR.A single typical S-box or a single P-box alone does not have much cryptographic strength: an S-box could be thought of as a substitution cipher, while a P-box could be thought of as a transposition cipher. However, a well-designed SP network with several alternating rounds of S- and P-boxes already satisfies Shannon's confusion and diffusion properties: The reason for diffusion is the following: If one changes one bit of the plaintext, then it is fed into an S-box, whose output will change at several bits, then all these changes are distributed by the P-box among several S-boxes, hence the outputs of all of these S-boxes are again changed at several bits, and so on. Doing several rounds, each bit changes several times back and forth, therefore, by the end, the ciphertext has changed completely, in a pseudorandom manner. In particular, for a randomly chosen input block, if one flips the i-th bit, then the probability that the j-th output bit will change is approximately a half, for any i and j, which is the Strict Avalanche Criterion. Vice versa, if one changes one bit of the ciphertext, then attempts to decrypt it, the result is a message completely different from the original plaintext -- SP ciphers are not easily malleable. The reason for confusion is exactly the same as for diffusion: changing one bit of the key changes several of the round keys, and every change in every round key diffuses over all the bits, changing the ciphertext in a very complex manner. Even if an attacker somehow obtains one plaintext corresponding to one ciphertext -- a known-plaintext attack, or worse, a chosen plaintext or chosen-ciphertext attack -- the confusion and diffusion make it difficult for the attacker to recover the key.Although a Feistel network that uses S-boxes (such as DES) is quite similar to SP networks, there are some differences that make either this or that more applicable in certain situations. For a given amount of confusion and diffusion, an SP network has more \"inherent parallelism\"and so — given a CPU with a large number of execution units — can be computed faster than a Feistel network.CPUs with few execution units — such as most smart cards — cannot take advantage of this inherent parallelism. Also SP ciphers require S-boxes to be invertible (to perform decryption); Feistel inner functions have no such restriction and can be constructed as one-way functions.".
• Substitution-permutation_network thumbnail SubstitutionPermutationNetwork2.png?width=300.
• Substitution-permutation_network wikiPageID "385162".
• Substitution-permutation_network wikiPageLength "6493".
• Substitution-permutation_network wikiPageOutDegree "49".
• Substitution-permutation_network wikiPageRevisionID "705273450".
• Substitution-permutation_network wikiPageWikiLink 3-Way.
• Substitution-permutation_network wikiPageWikiLink Advanced_Encryption_Standard.
• Substitution-permutation_network wikiPageWikiLink Avalanche_effect.
• Substitution-permutation_network wikiPageWikiLink Bijection.
• Substitution-permutation_network wikiPageWikiLink Bit.
• Substitution-permutation_network wikiPageWikiLink Bitwise_operation.
• Substitution-permutation_network wikiPageWikiLink Block_cipher.
• Substitution-permutation_network wikiPageWikiLink Category:Block_ciphers.
• Substitution-permutation_network wikiPageWikiLink Category:Cryptographic_algorithms.
• Substitution-permutation_network wikiPageWikiLink Category:Permutations.
• Substitution-permutation_network wikiPageWikiLink Chosen-ciphertext_attack.
• Substitution-permutation_network wikiPageWikiLink Chosen-plaintext_attack.
• Substitution-permutation_network wikiPageWikiLink Ciphertext.
• Substitution-permutation_network wikiPageWikiLink Confusion_and_diffusion.
• Substitution-permutation_network wikiPageWikiLink Cryptography.
• Substitution-permutation_network wikiPageWikiLink Data_Encryption_Standard.
• Substitution-permutation_network wikiPageWikiLink Diffusion.
• Substitution-permutation_network wikiPageWikiLink Exclusive_or.
• Substitution-permutation_network wikiPageWikiLink Execution_unit.
• Substitution-permutation_network wikiPageWikiLink Feistel_cipher.
• Substitution-permutation_network wikiPageWikiLink International_Data_Encryption_Algorithm.
• Substitution-permutation_network wikiPageWikiLink Key_(cryptography).
• Substitution-permutation_network wikiPageWikiLink Known-plaintext_attack.
• Substitution-permutation_network wikiPageWikiLink Malleability_(cryptography).
• Substitution-permutation_network wikiPageWikiLink One-way_function.
• Substitution-permutation_network wikiPageWikiLink PRESENT_(cipher).
• Substitution-permutation_network wikiPageWikiLink Permutation.
• Substitution-permutation_network wikiPageWikiLink Permutation_box.
• Substitution-permutation_network wikiPageWikiLink Plaintext.
• Substitution-permutation_network wikiPageWikiLink Product_cipher.
• Substitution-permutation_network wikiPageWikiLink Pseudorandomness.
• Substitution-permutation_network wikiPageWikiLink S-box.
• Substitution-permutation_network wikiPageWikiLink SAFER.
• Substitution-permutation_network wikiPageWikiLink SHARK.
• Substitution-permutation_network wikiPageWikiLink Smart_card.
• Substitution-permutation_network wikiPageWikiLink Square_(cipher).
• Substitution-permutation_network wikiPageWikiLink Substitution_cipher.
• Substitution-permutation_network wikiPageWikiLink Transposition_cipher.
• Substitution-permutation_network wikiPageWikiLink File:SubstitutionPermutationNetwork2.png.
• Substitution-permutation_network wikiPageWikiLinkText "SP-network".
• Substitution-permutation_network wikiPageWikiLinkText "SPN".
• Substitution-permutation_network wikiPageWikiLinkText "Substitution-permutation network".
• Substitution-permutation_network wikiPageWikiLinkText "Substitution-permutation_network".
• Substitution-permutation_network wikiPageWikiLinkText "substitution-permutation network".
• Substitution-permutation_network wikiPageUsesTemplate Template:Cite_book.
• Substitution-permutation_network wikiPageUsesTemplate Template:Cryptography_navbox.
• Substitution-permutation_network wikiPageUsesTemplate Template:Reflist.
• Substitution-permutation_network subject Category:Block_ciphers.
• Substitution-permutation_network subject Category:Cryptographic_algorithms.
• Substitution-permutation_network subject Category:Permutations.
• Substitution-permutation_network hypernym Series.
• Substitution-permutation_network type TelevisionShow.
• Substitution-permutation_network type Algorithm.
• Substitution-permutation_network type Combinatoric.
• Substitution-permutation_network type Function.
• Substitution-permutation_network type Redirect.
• Substitution-permutation_network comment "In cryptography, an SP-network, or substitution-permutation network (SPN), is a series of linked mathematical operations used in block cipher algorithms such as AES (Rijndael).Other ciphers that use SPNs are 3-Way, PRESENT, SAFER, SHARK, and Square.Such a network takes a block of the plaintext and the key as inputs, and applies several alternating \"rounds\" or \"layers\" of substitution boxes (S-boxes) and permutation boxes (P-boxes) to produce the ciphertext block.".
• Substitution-permutation_network label "Substitution-permutation network".
• Substitution-permutation_network sameAs Q1433692.
• Substitution-permutation_network sameAs Substitutions-Permutations-Netzwerk.
• Substitution-permutation_network sameAs شبکه_جانشینی_جایگشت.
• Substitution-permutation_network sameAs Réseau_de_substitution-permutation.
• Substitution-permutation_network sameAs Rete_a_sostituzione_e_permutazione.
• Substitution-permutation_network sameAs SPN構造.
• Substitution-permutation_network sameAs permutasjon-chiffer.
• Substitution-permutation_network sameAs m.0222rk.
• Substitution-permutation_network sameAs SP-сеть.
• Substitution-permutation_network sameAs Substitution-permutation_network.
• Substitution-permutation_network sameAs Substitutions-permutationskrypto.
• Substitution-permutation_network sameAs SP-мережа.
• Substitution-permutation_network sameAs Q1433692.
• Substitution-permutation_network sameAs 代换-置换网络.
• Substitution-permutation_network wasDerivedFrom Substitution-permutation_network?oldid=705273450.
• Substitution-permutation_network depiction SubstitutionPermutationNetwork2.png.
• Substitution-permutation_network isPrimaryTopicOf Substitution-permutation_network.