what is cryptography?

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Dan Boneh Introduction What is cryptography? Online Cryptography Course Dan Boneh

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Online Cryptography Course Dan Boneh. Introduction. What is cryptography?. Crypto core. Talking to Alice. Talking to Bob. Secret key establishment: Secure communication:. Alice. Bob. a ttacker???. m 1. k. k. m 2. c onfidentiality and integrity. - PowerPoint PPT Presentation

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Page 1: What is cryptography?

Dan Boneh

Introduction

What is cryptography?

Online Cryptography Course Dan Boneh

Page 2: What is cryptography?

Dan Boneh

Crypto core

Secret key establishment:

Secure communication:

attacker???

k k

confidentiality and integrity

m1

m2

AliceBob

Talking to Alice

Talking to Bob

Page 3: What is cryptography?

Dan Boneh

But crypto can do much more• Digital signatures

• Anonymous communicationAlice

signature

Alice

Who did I just talk to?

Bob

Page 4: What is cryptography?

Dan Boneh

Alice

But crypto can do much more• Digital signatures

• Anonymous communication

• Anonymous digital cash– Can I spend a “digital coin” without anyone knowing who I am?– How to prevent double spending?

Who was that?Internet

1$(anon. comm.)

Page 5: What is cryptography?

Dan Boneh

Protocols• Elections• Private auctions

Page 6: What is cryptography?

Dan Boneh

Protocols• Elections• Private auctions

• Secure multi-party computation

Goal: compute f(x1, x2, x3, x4)

“Thm:” anything the can done with trusted auth. can also be done without

trustedauthority

Page 7: What is cryptography?

Dan Boneh

Crypto magic• Privately outsourcing computation

• Zero knowledge (proof of knowledge)

Alice

searchquery

What did she search for?

results

I know the factors of N !!

proof π

???

E[ query ]

E[ results ]

AliceN=p q∙Bob

N

Page 8: What is cryptography?

Dan Boneh

A rigorous scienceThe three steps in cryptography:

• Precisely specify threat model

• Propose a construction

• Prove that breaking construction under threat mode will solve an underlying hard problem

Page 9: What is cryptography?

Dan Boneh

End of Segment