. . . ,

1
???????????? ??????? ??????

• ??????? ??????
• ?????, 2005 ?.

2
???????

• ?????????? ?????? ???? ???? ????? ???????
  ????????????? ????????????????? ?????????? ---
  ???? ??????? ???????????????? ? ??????????
  ?????????. ?????????. ????? ? ?????. ?????? ?????
  ????, ??? ??????????? ????????????????
  ??????????? ? ????????????? ????? ??????????, ??
  ?????? ???????? ??????? ?? ?????????? ???????????
  ??????????.
  ???? ?????? (Bruce Schneier)

3
????

• ????? 1 ??????? ?????
• ????? 2 ????????????
• ????? 3 ????????? ?????

• ??????
• ????????? ?????????????? ????????

4
????? 1 ??????? ?????

• ???????????? ?????????????
• ??????? ????????????? ????????? ????? ?????????
  ?? ????????? ????? ? ????? ????????????
  ?????????????? ???? ?????? ? ??????????????
  ?????.
• ?????????????? ?????? ???????????? ?????????
  ????????
• ??????????? (diffusion) - ?.? ????????? ??????
  ????? ????????? ?????? ??? ????? ?????? ??
  ??????? ????? ?????? ???????????, ??? ????????
  ?????????????? ???????? ????????? ??????
• ????????????? (confusion) - ?????????????
  ??????????????, ???????????? ?????????
  ?????????????? ???????????? ????? ????????????? ?
  ???????? ???????.

5
????????? ???????? ?????

• ???????? ????????? ?????????- ?????? ??????????
  ????? ?????? - ?????? ?????- ?????? ????????
  ?????- ????? ??????? ??????????
• ??????? ??????????
• ????? ??????? ??? ????????? ??????? ??????
• ????????????? ????????????

6
???????? DES Data Encryption Standard

• ????????????
• ???????? ??????????
• ?? ?????????? 1974-2000 ?.?.
• ????? ????? 64 ???
  ????? ????? 56 ??? ??????
  ????????? ???????? 48 ???
• ????? ??????? 16

???? ????????
7
???????? DES ????? ????????
8
????? ??????????? (S-boxes)

• S-boxes ??????? ??? ????, ????? ????????
  ??????????? ????? ??????? ? ????????????
• ? DES S-boxes c ??????? ????????????? ??????
  ??????????? 6-??????? ???? ? 4-??????? ?????,
  ?????????????? 48 ??? ????????????? ? 32
• ? ???? ???????????? ?????????? S-boxes

DES S-boxes
9
????? 2 ????????????

• ?????? ??? ?? ????? ?????????????

• ???????????? ??? ??????? ??????, ????? ???????
  ???????? ????? ? ???????????? ??????? ??????
  ????????????????? ??????????, ? ????? ????
  ????????? ??????.

10
????? 2 ????????????????????? ????

• Ciphertext Only ?????? ?? ?????? ??????
  ???????????
• Known Plaintext ?????? ?? ?????? ????????????
  ????????? ??????
• Chosen Plaintext ?????? ?? ?????? ??????????
  ????????? ??????
• Chosen Ciphertext ?????? ?? ?????? ??????????
  ???????????

11
????? 2 ?????????????? ????????

• ???????? ???????????? ??????? ?? ???? ?????
• ???????? ??????? ?????????? ? ?????
• ???????? ???????????? ????????? ??????
• ???????? ???????????? ???????? ???????

12
???????? ????????????????(Complementation
property)

• ??????????? ????? ?????? ?????-?????????? ???
  ????????? ?????? ? ?????
• ????????, ? DES
• ???? ??

13
????? 2 ?????????????????????????? ?????

• Brutal-Force Attack ????? ??????? ??????
  ????, ?.?. ?????? ????????? ??????
• ???????? ???? ?????? ?????? ?????????????
  ???????? ????? Brutal-Force Attack, ??? ????????
  ????????? ??????????? ?????/??????
• Key-recovery ????? ?????????? ????????
  ?????????? ?????????? ?????,? ??????? ????????
  ????????? ???????? ???????. ???????????? ?
  ??????????? ??????? ?????????????

14
????? 3 ????????? ?????

• ???????????????? ????????????
• ???????? ????????????
• ??????????? ????????????????? ? ?????????
  ????????
• ???????????????? ????????????
• ??????, ?????????? ?? ???????? ???????? ?????????

15
???????????????? ?????? ???????

• ?????????? ? 1990 ???? ???????????? ?????????????
  ??? ??????? (Eli Biham) ? ??? ??????? (Ali Shamir)

??? ?????
??? ?????
16
???????????????? ?????? ???????? ????

• Chosen-plaintext ?????
• ???????? ???? ??????? ??????? ? ?????????????
  ?????????, ???????, ??? ?????????? ????? ?? ???
  ?X X1?X2 ?Y Y1?Y2
• ?????????? ????? ????? ???, ??????? ????????
  ????????? ????

17
???????????????? ?????? ????? ????????

• ????? ? ????????? ???? S-box c n-??????? ?????? ?
  m-??????? ???????
• ???????????? ??? ???? ???????? ??????? ??????
  ? ???????? ???????? ?????? ?????? ??????????????
• ???? Q - ??? ?????????? ????????? ??? ??????,
  ?????? ???? ????????????, ?? pQ/2n ???????????
  ????? ?????????????
• ???????????????? ?????????????? ???
  ?????????????????? ????????? ????? ??????? ??????
  
• ???????? ???????????????? ?????????????? ??
  ??????? ? 1?? ?? ?????????????, ????????
  Key-recovery ????? ?? ????????? ??????.
• ??? ?????? DES ?????????? 247 ?????????? ????
  ??????? ???????
• ?????? ?????????????? ???????????? ???????????
  p, ??????????????? ?????????? S-boxes ? ??????
  ???????????????? ??????????????

18
???????? ?????????????

• ?????????? ??????? ?????? (Mitsuru Matsui) ?
  1992 ?.

??????? ??????
19
???????? ?????????????? ????

• Known plaintext attack
• ???? ???????? ??????????? ????? ???????? ???????,
  ???????????? ? ??????
• ????? ??????????? key-recovery

20
???????? ??????????? ????????

• ??????????? ?????????? ?????????? ?????,
  ?????????????????? ???????? ???????????? ?????
  ???????? ? ????????? ??????
• ??????????? ?????????? ??????????? ???,
  ????????????? ?????? ???? ????????? ??????,
  ??????????? ? ?????
• ??????????? ?????????? ????? ??????????
  (Piling-Up Lemma)
• Key-recovery ?? DES ???????? ??? ?????????????
  243 ????????? ???????? ???????
• ?????? ?????????????? ????????????? ????????
  (bias), ??????????????? ????? S-boxes, ??? ????
  ?????????? ?????????

21
???????? ??????? ????????????????? ? ?????????
???????

• ???????????????-???????? ????????????- chosen
  plaintext- ?????????? ?????????? ?????????
  ??????? ??? ?????????? ????????????????
  ??????????????- 10 ??? ????? 8-?????????? DES
  ??????????? ? ??????? ????? 512 ??????? ???????-
  ?????? ??????? ????????????? (?? ?????? 2-3
  ???????)
• ????????? (truncated) ?????????????- ?????? ????
  ?? ?????? ?????
• ????????????? ?????? ????????- ????????? ???????
  ???????????????? ??????????????- ????????,
  ?????? f(x)(xk)2 mod p- ?????? ?????
  ???????, ??????? ????? ??????? ????????
• ??????????? ????-?? (Miss-in-the-middle attack)-
  ???? ?????????????, ??????? ???????? ??
  ??????????, ???????? ????? ?????? ????????????
  ??????
• ????? ?????????- ???? 2 ????.?????????????? ?
  ???????? ?????????????, ??????????? ???? ????
  (?????????? ????? ???? chosen-ciphertext)

22
???????????????? ?????

• ?????? ?.????????? ? ?.???????, 1997 ???
• Known-text attack
• ????????????, ??? ????????? ??????? ?????????.
  ????? ???? ???? ????? ???? ??????? ??? ?????????,
  ?????-?? ??????? ?? ?????.
• ????????????? ???? ????????? ?? ??????????
  ???????? ?????????? ???????? ???????

23
??????, ?????????? ?? ???????? ???????? ?????????

• ????? ???????????? (Meet-in-the-middle)- ????
  ?????, ???????????? ?? 1? ? ????????? ??????? ??
  ????????????)
• ?????? (weak) ? ????-?????? (semi-weak) ?????-
  ?????, ??? ??????? ????????? ?????????? ?????????
  ????????? ? ??????????? ?????????????- ?????
  ?????? ???????, ?? ?????? ????? ????????
• ????? ????????? ??????- Chosen-plaintext
  attack- ? ??? ???? ??????????? ?????????
  ??????????? ???????, ?????????? ????? ?????

24
??????? ?????????????

• ???????? AES (Rijndael) ???????????
  ???????????? ???????? ??????????
• ?? ?????????? ??????? ?? ???? ?????????????? ????
  ????
• ??????, ? ?? ???? ??? ???????? ??????? ????,
  ???????????? ??????? ?????????????? ??????
  Square-saturation-integral-multiset attacks
• ???????? Square attack, ????????? ??????
  ????????? Square ??????? . Chosen plaintext
  attack, ?????????? ?? ??????? ?????? ?????????
  ???????? ???????- ???????? ???????????? ?????? -
  ???????????????- ??????????? ??????????
  ?????????? ???? ??? ???????????? ????? ?????????
  ???????? ???????

Vincent Rijmen
J. Daemen
25
????????? ?????????????? ????????

• ??? ? ??? ????????
• Bruce Schneier Self-Study Course in Block Cipher
  Cryptanalysis, 2000http//www.counterpane.com/se
  lf-study.html - ???? ???????? ?????, ?.?. ???
  ???, ??? ????? ??????? ???????? ??????????????
• http//www.distributed.net- ?????????? ?????????
  RC5 ?????? ?????????? ? ??????????? )
• Francois-Xavier Standaert others Cryptanalysis
  of Block Ciphers the Survey, 2001http//logic.p
  dmi.ras.ru/yura/crypto/01crypto.pdf- ?????
  ?????? ????? ??????? ?????????????, ?????? ?????
  ???????? ? ?????????? ????
• Dave Rudolf Development and Analysis of Block
  Ciphers and the DES System, 2002
  http//www.cs.usask.ca/grads/dtr467/400- ?????
  ???????? ???????? ? ?????? ??????? ??????, ??????
  ?????? DES
• ?. ??????, ??????? ?????????????????
  ?????????http//www.cryptography.ru/db/msg.html?
  mid1162999urinode4.html- ???????? ???????
  ????? ??????? ? ???????????? ?????????
  ?????????????, ?? ????? ??????? (???!) ?? ???????
  ?????