Cipher Techniques: Skytale, Caesar, Vigenere, Playfair, and Transposition

1. Jeff Ehme Spelman College jehme@spelman.edu Chris Christensen Northern Kentucky University christensen@nku.edu

2.

3.

4. Skytale Caesar cipher

5. Vigenere Cipher 16 th century Playfair Cipher 19 th century Transposition Cipher

8. KL47 KW-7

9. ATM IFF

10. Data Encryption Standard 1977 New Directions in Cryptography 1976

11. Symmetric key block ciphers Public key ciphers Stream ciphers Post-quantum ciphers

12. Substitution Transposition

13.

15. DROSX DOBOC DSXQW KDROW KDSMK VKCZO MDCYP ZELVS FUOIM SZROB CRKFO CZKBU ONSXD OBOCD LIWKD ROWKD SMCPK MEVDI SXDRO COMSZ ROBCK CKZZV SMKDS YXCYP WKDRO WKDSM CDRKD MKXLO ZBOCO XDONS XEXNO BQBKN EKDOM YEBCO CYPDO XSQXY BONRY GOFOB KBODR OWYNO BXZBS FKDOU OIMSZ ROBCD ROGYB URYBC OCYPM BIZDY QBKZR IWYNO BXZBS FKDOS OIMSZ ROBCK BOOAE KVVIW KDROW KDSMK VVISX DOBOC DSXQ

17. Lester Hill (1891 1961)

18.

19.

20. Symmetric Key vs Asymmetric key

21. Symmetric Key Asymmetric Key

22. If the solution to a problem can be quickly verified by a computer, can the computer also solve that problem quickly?

23. Horst Feistel (1915 1990) Simplified DES: Wade Trapp and Lawrence Washington

25. DES 64-bit block 56-bit key (8 parity bits) 8 S-boxes 6 x 4 16 rounds Feistel cipher 12-bit block 9-bit key 2 S-boxes 4 x 3 4 rounds Feistel cipher Simplified DES

26.

27.

28. 9 bits of key 111 010 110 Use the 8 bits on the left for k1 1110 1011 Rotate to the left one bit 110 101 101 Use the 8 bits on the left for k12 1101 0110 Rotate to the left 1 bit 101 011 011 Use the 8 bits on the left for k3 1010 1101 Rotate to the left 1 bit 010 110 111 Use the 8 bits on the left for k4 0101 1011

29.

32. Encryption Decryption

33. Encryption Decryption

34. Backdoor?

35.

36. Perfect Security Random key, as long as the message, and used only once. Computational Security Today 112

37.

39. Skipjack declassified 1998 Clipper Chip 1993 -1996 64-bit block 80-bit key 32 rounds Unbalanced Feistel cipher

40. Claude Shannon (1916 2001)

41. A Mathematical Theory of Communication 1948 The Theory of Secrecy Systems 1949

42. Diffusion : the statistical structure of [the message] which leads to its redundancy is dissipated into long range statistics. Wire crossing, S-box Confusion : make the relation between the simple statistics of [the ciphertext] and the simple description of [the key] a very complex and involved one. Permutation, P-box

43.

44. Many

45. 64-bit block 80- or 128-bit key 1 S-box 4 x 4 31 Rounds Substitution-Permutation Network

46.

48.

50. How do they know its secure?

51. Joan Daemen and Vincent Rijmen Simplified AES: Mohammad Musa, Edward Schaefer, and Stephen Wedig

52. AES 128-bit block 128-bit, 192-bit, or 256-bit key 10, 12, or 14 rounds SPN 16-bit block 16-bit key 2 rounds SPN Simplified AES

53.

54.

55.

56.

57.

58. Serpent Twofish RC6 MARS

59. Simplified IDEA Hoffman, N. 2007. A Simplified IDEA Algorithm, Cryptologia 31(2), 143 151. TEA Holden, J. 2013. Demitasse: A Small Version of the Tiny Encryption Algorithm and Its Use in a classroom Setting. Cryptologia 37(1), 74 83.

60. Stream ciphers

61. Simplified DES Trappe, W. and Washington, L. Introduction to Cryptography with Coding Theory Simplified IDEA Hoffman, N. 2007. A Simplified IDEA Algorithm, Cryptologia 31(2), 143 151.

62. PRESENT Boganov, A. and others. 2007. PRESENT: An Ultra-Lightweight Block Cipher. (Search the net.) Simplified AES Musa, A., Schaefer, E., and Wedig, S. 2010. A Simplified AES Algorithm and Its Linear and Differential Cryptanalysis, Cryptologia 27(12), 148 177.

63. TEA Holden, J. 2013. Demitasse: A Small Version of the Tiny Encryption Algorithm and Its Use in a classroom Setting. Cryptologia 37(1), 74 83. Cryptology course notes and student-produced software http://www.nku.edu/~christensen/1301cscmat483.htm