Do you know the origin of Cryptography? How does public key authentication, digital signatures, certificates, and HTTPS works? Have you heard of the Diffie-Hellman protocol? If the answer is YES, feel free to skip this lecture. Otherwise - attend and learn more about the history of cryptology, classic and modern ciphers and some of their practical applications.

1. A Gentle [re]Introduction to
Cryptography
Mihailo Joksimovic

2. About me
● Lead Developer @ JAGGAER
● MSc Data Science student
● > 10 years in industry

5. ?

6. Scytale, 7 BC

7. By Matt_Crypto - http://en.wikipedia.org/wiki/File:Caesar3.png
Caesar cipher

8. Source: Wikipedia
Enigma machine

9. Symmetric ciphers

10. Source: https://www.electrodummies.net/en/symmetric-encryption/

11. Symmetric ciphers
● Data Encryption Standard - DES
○ 1970s
○ Deprecated
● Advanced Encryption Standard - AES
○ 2001
○ In use today

12. Problem?

14. Asymmetric cryptography

15. Diffie-Hellman key
exchange

16. Source: https://security.stackexchange.com/questions/45963/diffie-hellman-key-exchange-in-plain-

17. Source: https://security.stackexchange.com/questions/45963/diffie-hellman-key-exchange-in-plain-

18. Source: https://security.stackexchange.com/questions/45963/diffie-hellman-key-exchange-in-plain-

19. Source: https://security.stackexchange.com/questions/45963/diffie-hellman-key-exchange-in-plain-

20. Source: https://security.stackexchange.com/questions/45963/diffie-hellman-key-exchange-in-plain-

21. Source: https://security.stackexchange.com/questions/45963/diffie-hellman-key-exchange-in-plain-english

22. Public-key Infrastructure
(PKI)

24. Public-key cryptography
● RSA (Rivest–Shamir–Adleman) cryptosystem
○ Published in 1977
○ Still in use today
● Protocols using public keys
○ TLS (Transport Layer Security)
○ PGP (Pretty Good Privacy)
○ Bitcoin
○ ...

25. Hash functions

28. Hash examples (MD5)
● Input: “PHP Serbia”
Output: “5E7E1CCC0B57EB88248F7999B8C8D41B”
● Input: “PHP Sirbia”
Output: “FF5FA67F37BDF08DD10D989C4C47B481”
● Input: “PHP Serbia meetup at Humanity”
Output: “E975113F35B4D799DA4780B79A962CB9”

34. Transport Layer Security
● Used by HTTPS
● TLS
○ Successor of SSL 3.0
○ 1.2 (August 2008; currently active)
● TLS 1.3
○ August 2018
○ Still not widely used

35. TLS Handshake

36. Source: https://www.thesslstore.com/blog/tls-handshake-failed/

37. Source: https://www.thesslstore.com/blog/tls-handshake-failed/

38. Source: https://www.thesslstore.com/blog/tls-handshake-failed/

39. Source: https://www.thesslstore.com/blog/tls-handshake-failed/

40. Source: https://www.thesslstore.com/blog/tls-handshake-failed/

41. Source: https://www.thesslstore.com/blog/tls-handshake-failed/

42. Source: https://www.thesslstore.com/blog/tls-handshake-failed/

43. Source: https://www.thesslstore.com/blog/tls-handshake-failed/

44. Source: https://www.thesslstore.com/blog/tls-handshake-failed/

45. Source: https://www.thesslstore.com/blog/tls-handshake-failed/

47. Questions?

48. Thank you!
@GlavniProgramer
/MihailoJoksimovic
/MihailoJoksimovic