1. B504/I538: Introduction to Cryptography
Spring • Lecture 1
(2017—01—10)

2. Administrivia

3. Instructor: Ryan Henry
Office hours: 10:30 — 11: (or by appointment)
  
 LH 330e
- Alas, Ryan is stuck in Washington DC today ; - (

4. Associate Instructor (AI)
Instructor: Swami Ramesh
Office hours: 13:30 — 14: (or by appointment) 
 LH 330a

5. Required textbook Introduction to Modern Cryptography (2nd edition)
Jonathan Katz and Yehuda Lindell Chapman & Hall/CRC Cryptography and Network Security Series November 2014
Katz’ website 
IU Bookstore  * *
CRC Press  *
Amazon 

6.  http://homes.soic.indiana.edu/henry/courses/b609/s17
Course website 
The course website is the official source for:
assignments,
lecture slides,
important announcements,
supplemental material,
etc.
Please check the course website frequently!
Also, Canvas: 

7. Tuesdays and Thursdays
Lectures
(presumably you’ve already
figured this out)
Tuesdays and Thursdays
@ 13:00—14:15
in Ballantine Hall (BH) 322

8. A: Only if you want answers (in other words: YES, PLEASE DO!)
Should I interrupt with
questions during lectures?
Only if you want answers
(in other words: YES, PLEASE DO!) A:

9. Grading and assessment
80%
20%
10%
written assignments
in-class quizzes
participation
8 assignments at 10% each
4 quizzes at 5% each
110%
total
(Lowest assignments automatically be dropped)

10. Grading and assessment
A+ 97% B+ 87% C+ 77% D+ 67%
A 93% B 83% C 73% D 63%
A- 90% B- 80% C- 70% D- 60%

11. Homework ASK FOR HELP EARLY!
One assignment assigned every second Tuesday*
Due before Tuesday lecture two weeks later
Mostly written with some coding problems
ASK FOR HELP EARLY!
We will stop providing help starting 10 days after assignment is distributed!
* with a few exceptions ― see the calendar

12. Homework (sample timeline)
office
hours
assignment distributed
Sun Mon Tue Wed Thu Fri Sat
week N:
office hours
Sun Mon Tue Wed Thu Fri Sat
week N+1:
last day
for help!!
Sun Mon Tue Wed Thu Fri Sat
week N+2:
assignment
due
(next assignment distributed)

13. Typesetting with ￯ Q: By a show of hands, who here knows ￯?
- If your hand is not up, good news: you get to learn ￯!!
Written portion of assignments must be typeset using ￯
We will give you the ￯ source for every assignment
SoIC has a site license for ShareLaTeX 

14. Umm … Never! A: When do we start talking about cartography?
(this class is about cryptography!) A:

15. Well what in the @#%★‽! is
Huh!? No maps??
Well what in is
“cryptography”?

16. What in the @#%★‽! is Cryptography ?
And, more generally, what is this course all about?

17. What is this class all about?
Short answer: The theoretical foundations of modern cryptography
Cryptography ⊆ mathematics
No specific background is assumed, but “mathematical maturity” will help
We will cover the necessary math as we go!

18. What is this class all about?
On the other hand, physicists like to say that physics is to math as sex is to masturbation

19. What is this class all about?
NOT
What is this class all about?
Cartography, for starters
But also:
particulars of deployed encryption schemes
specific “hard” problems
how to implement， use, or break specific cryptographic software
ADVICE: Don’t try to implement crypto yourself!

20. I will make you write lots of proofs
*gasp!*
I will make you write lots of proofs
statement 1
statement 2
statement 3 ⋮
statement n
I don’t see why
statement 2
follows from
statement 1
NO MARKS FOR YOU!
Victor
(the verifier)
Peggy
(the prover)

21. I will make you write lots of proofs
I231: Introduction to the Mathematics of Cybersecurity
*gasp!*
I will make you write lots of proofs
Victor is very thorough yet very lazy
- will catch every mistake you make…but
- cannot be bothered to supply missing details
A perfectly valid complaint for Victor:
“I don’t understand!”
(or even, “This is poorly written”)
Victor
(the verifier)

22. NO!! WAIT! So it’s all math and proofs? It’s not just any math and
(See ya—I’m dropping!)
NO!! WAIT!
It’s not just any math and
proofs…it’s super important，
super cool math and proofs!

23. “Core” crypto Key establishment Secure communication   m1 m2
confidentiality/integrity

24. More advanced crypto
Digital signatures
Bob signed
this
message

25. More advanced crypto Who am I talking to??? Digital signatures
Anonymous communications
Who am
I talking
to???

26. More advanced crypto What am I computing for Bob?? Digital signatures
Anonymous communications
Oblivious computation
What am I
computing
for Bob??

27. Who just paid for that widget?
More advanced crypto
Digital signatures
Anonymous communications
Oblivious computation
Anonymous digital currencies
Who just paid for that widget? Ƀ

28. Cryptographic protocols
End-to-end verifiable elections
(as if anybody ever suspected an election was rigged!)
Election
authority
and the
winner
is…

29. Cryptographic protocols
End-to-end verifiable elections
(as if anybody ever suspected an election was rigged!)
Secure multiparty computation x2 x4
f(x1，x2，x3，x4，x5) x1 x5 x3

30. Crypto magic And a whole lot more… Proofs of Group signatures
data possession
Group signatures
Multiparty computation
Commitment schemes
Homomorphic
encryption
Zero-knowledge proofs
Secret sharing
Oblivious transfer
Private information retrieval
Deniable
messaging
Differential privacy
Verifiable outsourced computation
And a whole lot more…

31. Modern cryptograpy == Science
Three steps in modern crypto
propose a precise threat model
propose a construction
prove that breaking construction is “equivalent” to solving an intractable problem (or impossible)

32. That’s all for today, folks!
Thursday’s lecture: Discrete probability 101