Lecture 12-Anonymous Communication, Cryptocurrencies

Question 1

Review: What does IP authentication header protocol support?

Answer 1

authentication and integrity

Question 2

Review: What does Encapsulating Security Protocol do?

Answer 2

Authentication and encryption

Question 3

What is Wired Equivalent Privacy (WEP)?

Answer 3

Symmetric shared key authentication for protecting wireless traffic (not safe)

Question 4

WPA2

Answer 4

better than WEP, having a separate authentication server is a good thing because it could offer authentication for different points

Question 5

EAP (Extensible Authentication Protocol)

Answer 5

Allows client and Authentication server to mutually authenticate each other and do 4 key exchange (Part of TLS)

Question 6

How is WPA2 better than WEP?

Answer 6

Uses CBC-MAC and AES instead of RC4

Question 7

Onion Routing

Answer 7

Supports anonymous communication over a computer network. Bounces around the communication before reaching endpoint (encrypted IP header)

Question 8

How do you send response back with onion routing?

Answer 8

Each router has IP and ID of previous location so it sends it back there and is re-encrypted in the onion manner as it goes back

Question 9

Tor

Answer 9

2nd generation onion router
-overlay consisting of entry guard, middle relay, and exit relay
It’s encrypted in this overlay and is not encrypted once it goes to destination

Question 10

What is a hidden service?

Answer 10

Tor allows people to connect to a service without revealing the service’s IP address

Question 11

How do Tor clients find a hidden server?

Answer 11

Bob uses 3 introduction points to advertise himself. Alice will use rendezvous point to connect (lot of latency)

Question 12

Does Tor have perfect forward secrecy?

Answer 12

Yes, it refreshes public keys for every session so no prior information can be hacked.

Question 13

How are bitcoin transaction anonymous?

Answer 13

The public key which identifies a person is hashed

Question 14

Double Spending

Answer 14

When alice sends the same check to two people at the same time so that both of them give their goods

Question 15

How is double spending prevented?

Answer 15

Transactions get voted on to decide which one is valid if this happens

Question 16

How are transactions verified?

Answer 16

Merkle tree. Only need a few transactions to verify the hashes and blockchain stores chained hashes of every transaction ever

Question 17

Proof of work

Answer 17

The competition to find the hash with the correct number of prepending zeros in order to mine a block (gets rewarded in bitcoin)

Question 18

What is a limitation that actually could help prevent double spending?

Answer 18

Wait 10 minutes for verification of a transaction (waiting for confirmation)

Question 19

Can your public key be tracked?

Answer 19

You can create multiple public keys to keep anonymous but it can be linked together