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MODES OF OPERATION - PowerPoint PPT Presentation

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MODES OF OPERATION
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  1. MODES OF OPERATION

  2. 2-D Encryption Mode Ahmed A. Belal Moez A. Abdel-Gawad

  3. P = < P1 P2 P3 … P16 > Each Pi = < Pi1 Pi2 Pi3 … Pi16 > P1 P2 P16 R1 R2 R16 10110010 00100100 10100101 10010010 01001001 10111000 K 00010001 01010101 11011011 10101010 01010101 10011010 10011001 00100100 10100101 10000011 11011011 10010010 10010111 10101010 11100011 10011010 00111100 11100011 11000011 10000011 10010111 00111100 00010001 11000011 10111000 10100101 10100101 10011001 01001001 K 10110010 10011010 10110010 01010101 10010111 01001001 00010001 11000011 10000011 10011010 11011011 11000011 10101010 11100011 00111100 11100011 00111100 00010001 10010010 01001001 K 10100101 10011001 10100101 10010010 10111000 10100101 00100100 10000011 10010111 10110010 10100101 10111000 10101010 11011011 01010101 10011001 00100100 K 10110010 11000011 10010111 10100101 11100011 10010010 00111100 10011010 10100101 10000011 10111000 10011001 K 10101010 11011011 01010101 01001001 00010001 10010010 10101010 01010101 10011010 00111100 00100100 10100101 00010001 10111000 10110010 11000011 01001001 10000011 11100011 10100101 10011001 00100100 K 11011011 10010111 S1 Q1 S2 Q2 Q16 S16 Then C = < C1C2C3… C16> Where Each Ci = < S1i S2i S3i … S16i > 2DEM Each Qi = < Qi1 Qi2 Qi3 … Qi16 > Set Each Ri = < Q1i Q2i Q3i … Q16i > Each Si = < Si1 Si2 Si3 … Si16 >

  4. P11 P12 P11 P12 P21 P22 P11 P12 P21 P22 P31 P32 P21 P22 P31 P32 P41 P42 P41 P42 P51 P52 P61 P62 P31 P32 P51 P52 P61 P62 P71 P72 P81 P82 P91 P92 P41 P42 P71 P72 P81 P82 P101 P102 P111 P112 P121 P122 BPR = 2 BPR = 3 P51 P52 P61 P62 P71 P72 P11 P12 P21 P22 P31 P32 P41 P42 P81 P82 P51 P52 P61 P62 P71 P72 P81 P82 BPR = 1 BPR = 4 2DEM BPR = Blocks Per Row

  5. 2DEM • Works great with images • BPR value and Key needed • Resistance to certain attacks due to interleaving

  6. Accumulated Block Chaining Mode Lars R. Knudsen

  7. P1 P2 P3 Pm C1 h(x) H2 h(x) H3 C2 H1 C0 H0 Hm Cm C3 ABC 10000011 10100101 10100101 11100011 11000011 00111100 10011010 00010001 10111000 K 10011001 10010010 01010101 11011011 10101010 10010111 00100100 01001001 10110010 00100100 01001001 10100101 10010111 K 10110010 11011011 10010010 10101010 01010101 10011010 11100011 10000011 00111100 00010001 10111000 10100101 10011001 11000011 10101010 01010101 10010010 11011011 10110010 00100100 K 01001001 10100101 10010111 10000011 10011001 10100101 10111000 11000011 10011010 00111100 11100011 00010001 01001001 10010111 10011001 K 10101010 11011011 01010101 10010010 10110010 00100100 11100011 11000011 00111100 10011010 00010001 10000011 10111000 10100101 10100101 Where h(x) = x or h(x) = x<<1

  8. ABC • Has infinite error propagation • Authentication is not intended as part of mode • Infinite error propagation provides more diffusion • 2 initial vectors and Key needed • The mode acts more like a giant block cipher • Resists birthday attacks

  9. Key Feedback Mode Johan Håstad Mats Näslund

  10. P m bits K1 R m bits K2 R BRm BRm K3 R BRm m bits m bits KL R BRm KFB 10111000 10100101 10011001 10011010 00111100 11000011 11100011 10000011 10100101 00100100 10110010 10010111 10101010 11011011 01010101 K 10010010 00010001 01001001 01010101 11100011 00010001 10011010 00111100 11000011 10010111 10100101 10110010 10111000 00100100 10010010 10000011 11011011 10100101 10011001 10101010 K1 01001001 01001001 10010010 10010111 10110010 10100101 00100100 01010101 11100011 11011011 10101010 00111100 10011001 10100101 10111000 00010001 10011010 11000011 K2 10000011 10010111 11000011 10101010 11011011 01010101 00100100 10010010 01001001 10100101 10110010 00111100 10011010 00010001 10000011 10111000 10100101 10011001 KL-1 11100011 Where R is mxn matrix and B is multiplication of R and Ki mod 2

  11. KFB • Random Bit Generator • Initial matrix, constant, and Key needed • Does not assume that the block cipher is a pseudo-random permutation • Does assume that one or more iterations of the block cipher (with varying keys and a fixed plaintext) are hard to invert • Under this assumption, the KFB outputs are pseudo-random

  12. Propagating Cipher Feedback Mode Henrick Hellström

  13. L = # of plaintext blocks P = (P1, P2, … PL) Each Pi is m bits long n = number of bits in the key m = number of bits in each plaintext block IV T >> m P0 P1 PL mod 2m T CL << n-m C1 mod 2m mod 2m T << n-m >> m C0 PCFB 11100011 00111100 10011010 00010001 10011001 10100101 10110010 10100101 10010111 11000011 01001001 10000011 K 10101010 10111000 01010101 00100100 10010010 11011011 11100011 10110010 00010001 10011010 00111100 11011011 10010010 01001001 10010111 11000011 10000011 10100101 10100101 10011001 10101010 K 01010101 00100100 10111000 01001001 10010010 K 01010101 10101010 10110010 00100100 10010111 10000011 11000011 10100101 10011010 10111000 10100101 10011001 00010001 00111100 11100011 11011011

  14. PCFB • Has two way error propagation • Claims that no additional authentication is needed • Authentication mode was proposed • Initial vector and Key needed

  15. AES-hash Bram Cohen Ben Laurie

  16. H0 HASH Hm 2256-1 H3 Hm H2 H1 H0 AES-hash 10110010 10010111 10100101 11100011 11000011 00111100 10011010 00010001 10011001 10000011 10100101 01001001 10010010 11011011 10111000 10101010 01010101 00100100 P1 11000011 10100101 10010111 01001001 10010010 10101010 01010101 11011011 00100100 P2 10110010 00111100 00010001 10000011 10111000 10100101 10011001 10011010 11100011 11011011 10110010 00100100 10101010 01001001 01010101 10010111 10010010 P3 00010001 10100101 11100011 10100101 10111000 10000011 10011001 10011010 11000011 00111100 Pm 10110010 01001001 10010010 10000011 11011011 10101010 01010101 10100101 00100100 10011001 11100011 11000011 00111100 10011010 00010001 10111000 10100101 10010111 01001001 00100100 01010101 10100101 10101010 Hm 10110010 11011011 10010111 10011010 11000011 00111100 00010001 10000011 10111000 10100101 10011001 10010010 11100011 P is padded with 0’s to the next odd multiple of 128 bits and then appended with the 128-bit Big Endian encoding of the number of bits in the original file. Each Pi is 256 bits.

  17. AES-hash • Uses AES-256 • Variation of the Davies-Meyer hash construction • Using last step prevents an adversary from creating a new hash for a related message • Only the Key is needed

  18. QUESTIONS