CS284BlockCiphers

CS284BlockCiphers - Block Ciphers CSCI 284/162 Spring 2009 GWU Some of this slide set is from Section 2 H M Heys"A Tutorial on Linear and

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CSCI 284/162 Spring 2009 GWU Some of this slide set is from Section 2, H. M. Heys, "A Tutorial on Linear and Differential Cryptanalysis", Technical Report CORR 2001-17, Centre for Applied Cryptographic Research, Department of Combinatorics and Optimization, University of Waterloo, Mar. 2001. (Also appears in Cryptologia, vol. XXVI, no. 3, pp. 189-221, 2002.) The Heys’ reference is considered indispensable for this lecture, i.e., it is compulsory reading Block Ciphers
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09/03/10 CS284-162/Spring09/GWU/Vora/Block Ciphers. 2 Substitution-Permutation Networks (SPNs) Basic building block of several symmetric-key block ciphers (AES): A substitution A permutation A pad with key Repeated over many “rounds”
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09/03/10 CS284-162/Spring09/GWU/Vora/Block Ciphers. 3 Single SP block From: Hey’s paper “S” block permutations One part of key
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09/03/10 CS284-162/Spring09/GWU/Vora/Block Ciphers. 4 Example S-box 0 A 8 E 1 F 9 0 2 3 A C 3 9 B 1 4 B C 5 5 8 D 6 6 2 E D 7 4 F 7 0000 1010 0001 1111 0010 0011
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09/03/10 CS284-162/Spring09/GWU/Vora/Block Ciphers. 5 1011 0101 0100 0110 1000 0111 1001 1100 Example Permutation 0 0 8 2 1 4 9 6 2 8 A A 3 C B E 4 1 C 3 5 5 D 7 6 9 E B 7 D F F
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09/03/10 CS284-162/Spring09/GWU/Vora/Block Ciphers. 6 Example
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09/03/10 CS284-162/Spring09/GWU/Vora/Block Ciphers. 7 Invert single box?
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09/03/10 CS284-162/Spring09/GWU/Vora/Block Ciphers. 8 Example
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09/03/10 CS284-162/Spring09/GWU/Vora/Block Ciphers. 9 4 Rounds Inversion: No permutation before mixing
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09/03/10 CS284-162/Spring09/GWU/Vora/Block Ciphers. 10 Example Encryption and Decryption
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09/03/10 CS284-162/Spring09/GWU/Vora/Block Ciphers. 11 General Iterated Block Cipher Plaintext is divided into blocks of size n A single key K is used to generate N r keys: K (1) , K (2) , … K (N r ) through a key schedule A round function , g , is used to repeatedly encrypt the plaintext N r times, each time using a key generated by the key schedule
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09/03/10 CS284-162/Spring09/GWU/Vora/Block Ciphers. 12
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CS284BlockCiphers - Block Ciphers CSCI 284/162 Spring 2009 GWU Some of this slide set is from Section 2 H M Heys"A Tutorial on Linear and

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