More Secrets of Cryptography

Transcript

1. More Secrets of Cryptography Chris Riley ConFoo 2018 1
2. Introduction
3. Why do we need cryptography? 1
4. Modern cryptography • Confidentiality 2
5. Modern cryptography • Confidentiality • Key exchange 2
6. Modern cryptography • Confidentiality • Key exchange • Identity 2
7. Modern cryptography • Confidentiality • Key exchange • Identity • Authentication 2
8. Symetric vs Asymetric Cryptography
9. Eliptic Curve Cryptography
10. Eliptic Curve Equation • y2 = x3 + ax2 + b 3
11. Eliptic Curve Equation • y2 = x3 + ax2 + b • y2 = x3 + 486662x2 + x 3
12. An Eliptic Curve 4
13. Eliptic curve dot function 5
14. Eliptic curve multiplication function 6
15. Eliptic curve for Cryptography 7
16. Eliptic Curve Key Exchange • Agree a curve, modulus and generator point (G) 8
17. Eliptic Curve Key Exchange • Agree a curve, modulus and generator point (G) • Select random integer d and compute P = dG 8
18. Eliptic Curve Key Exchange • Agree a curve, modulus and generator point (G) • Select random integer d and compute P = dG • Exchange public keys (PA and PB) 8
19. Eliptic Curve Key Exchange • Agree a curve, modulus and generator point (G) • Select random integer d and compute P = dG • Exchange public keys (PA and PB) • Compute a shared secret dBPA and dAPB 8
20. Eliptic Curve Key Exchange • Agree a curve, modulus and generator point (G) • Select random integer d and compute P = dG • Exchange public keys (PA and PB) • Compute a shared secret dBPA and dAPB • Both parties have now computed dAdBG 8
21. Key Exchange protocol 9
22. Man in the middle 10
23. The Web of Trust
24. Trent, the trusted third party 11
25. Can you trust a web of trust? 11
26. Cryptographic Hash functions
27. Ideal hash function properties • It should be quick and easy to compute a hash for any given data. 12
28. Ideal hash function properties • It should be quick and easy to compute a hash for any given data. • It should be difficult to compute data that has a given hash. 12
29. Ideal hash function properties • It should be quick and easy to compute a hash for any given data. • It should be difficult to compute data that has a given hash. • It should be unlikely that two different messages will have the same hash. 12
30. SHA-2
31. Setup phase • Append a single ’1’ bit to the data • Pad the data with ’0’ so that the data + 64 bits is a multiple of 512 • Append the data length as a 64 bit integer 13
32. Expansion phase • Split message into 512 bit blocks • Expand each block to 2048 bits • Expansion is done using shifts and rotates of the original block xor’d together 14
33. Compression phase 1By User:kockmeyer (Own work) CC-BY-SA-3.0, via Wikimedia Commons 15
34. Merkel Trees
35. A Merkel Tree 16
36. A Merkel Tree 17
37. Bitcoin
38. What is a blockchain? • A Merkle tree 18
39. What is a blockchain? • A Merkle tree • No central authority 18
40. What is a blockchain? • A Merkle tree • No central authority • Multiple ’forks’ may exist 18
41. What is a blockchain? • A Merkle tree • No central authority • Multiple ’forks’ may exist • There exists a consensus algorithm to determine the correct fork 18
42. What is a blockchain? • A Merkle tree • No central authority • Multiple ’forks’ may exist • There exists a consensus algorithm to determine the correct fork • The consensus algorithm only requires data contained on the blockchain to run 18
43. Mining a bitcoin 19
44. Why do bitcoins have value? 19
45. Should I use a block chain for ... ? 19
46. Thanks • @giveupalready • https://github.com/carnage • https://carnage.github.io 20