RSA in Ruby for begginers

I gave this talk to people on XING Porto.

It talks about how RSA works and give some examples in plain Ruby.

Transcript

1. RSA In Ruby for beginners
2. I'm Matheus Brazilian Dogs — About me
3. About me XING # ProBusiness team (aka Spiderman Team) Backend Developer Working with Ruby since 2012
4. Introduction Rivest, Shamir, and Adleman Public/private encryption algorithm Widely used in the market
5. In order to understand how it works, let’s imagine something: Alice and Bob want to.... How it works
6. How it works
7. How it works
8. How it works
9. Generating keys - p, q Must follow some rules: ! be different from each other; ! be random integers; ! be similar in magnitude; ! be prime; ! be very large. 2048 digits to be considered safe;
10. Generating keys - p, q
11. Generating keys - p, q
12. Generating keys - n
13. Carmichael’s totient function => lcm(p — 1, q — 1) Older specifications: (p — 1) * (q — 1) Generating keys - totient
14. Generating keys - totient
15. Generating keys - e
16. Generating keys - d
17. Generating keys - d
18. Encrypting c = (Mˆe) % n
19. Encrypting
20. Padding scheme RSA implementations usually implements a structured padding before encrypting A great padding scheme ensures that a message doesn’t turn into a predictable message structure PKCS#1, RSA-PSS
21. Padding scheme Simple padding scheme based on the string size and bytes a % b is never higher than b every encrypted char must have the same size, if not, fill it with zeros
22. Padding scheme "Hello" 72, 101, 108, 108, 111 1622, 52, 1504, 1504, 411 1622, 0052, 1504, 1504, 0411 16220052150415040411
23. Decrypting M = (cˆd) % n
24. Decrypting
25. Downsides Choosing small values for p and q make the algorithm faster, but it can be easily broken down RSA has a deterministic nature Padding schemes can be fragile
26. Does it work?
27. Does it work?
28. Thanks!