Lecture 13-Hardware Security

Question 1

Recall: Onion routing vs Tor

Answer 1

Onion routing allows for multiple nodes, Tor only allows for 3 intermediary nodes

Question 2

Recall: What is the basic process of a Tor circuit?

Answer 2

Keep extending the circuit (request node a to connect me to node c and then request node c to pass along the connection)

Question 3

Zerocoin summary

Answer 3

Alice generates serial number s, random r which will reveals serial number S and commits a coin C. Alice spends the zerocoin and the equal amount of bitcoin gets added to a pool. To redeem zerocoin, make it clear that the coin C belongs to the zerocoin set and that I know how to reveal the serial number since I have r and post that. Miners verify this proof and then the bitcoin gets transferred from the zerocoin escrow pool

Question 4

How is zerocoin anonymous?

Answer 4

It relies on a zkp the coin is not linked to a specific coin in the set of zerocoins. It is not linked to the serial number.

Question 5

Can you double spend with zerocoin?

Answer 5

No because you can’t double spend without reusing the serial number which would be detected by the verifiers.

Question 6

What is a side channel attack?

Answer 6

It is a non-invasive, passive attack where the attacker looks for changes in sound, heat, power, etc, and tries to see if it leaks any information

Question 7

What would need to happen for a timing attack to be possible?

Answer 7

Timing variations would need to exist on the basis of the value of a secret key, There needs to be a way to measure that variation

Question 8

What is the problem with repeated squaring algorithm?

Answer 8

It leaks information if you do SPA (simple power analysis). Uses more power for multiplication which is only done when secret key is 1.

Question 9

Countermeasures to SPA

Answer 9

generate random noise, add delays independent of key, shield the side channel leakage

Question 10

What is a hardware trojan?

Answer 10

An addition or modification to a circuit with malicious intent (adding another circuit to bypass encryption for example)

Question 11

How can a design be manipulated to include hw trojan?

Answer 11

So take F(x) = x^2 to authenticate a user only for users 0-9. Bob can create a circuit where in addition to 0-9. 10 and 11 get authenticated as well (malicious). Ideally, those should get invalidated.

Question 12

How to detect hardware trojan?

Answer 12

Do the same thing attackers do. Side channel analysis. Pros is that it could reveal a hardware trojan but cons is that it could have a high false alarm rate if the hardware has errors and analyzers think it is a hw trojan

Question 13

PUF

Answer 13

physical unclonable function: Hardware analog is a one-way function and each puf is unique and you cannot predict the response due to various random delays and changes

Question 14

What is a vulnerability of PUF?

Answer 14

Prone to error. So if you want to reverse and get back your secret key, it will require some extra processing

Question 15

Silicon puf

Answer 15

Create n-bit response by sending it challenges that excites two paths and detect which path was faster (0 or 1)

Question 16

Strong PUF

Answer 16

-used for authentication, has many challenge-response pairs

Question 17

Weak PUF

Answer 17

-only a small number of challenge-response pairs, used to do things like digitize a fingerprint

Question 18

What is a Trusted Platform Module?

Answer 18

A chip integrated into a platform to keep information extra secure

Question 19

Key components of TMP architecture?

Answer 19

You can opt-in or out, non-volatile memory is used to store long term keys and data authorization, PCR (platform configuration registers) is used to store integrity metrics of code

Question 20

TMP function (integrity measurements)

Answer 20

-used to report the integrity of firmware, OS, loaders

Question 21

TPM function (remote attestation)

Answer 21

TPM creates and signs a hash summary of hardware configuration for requester as verification that it has not changed

Question 22

TPM function (Protected storage)

Answer 22

Seal the data storage and is only accessible (decryptable) if it is in the same state it was when encrypted

Question 23

TPM key hierarchy overview

Answer 23

Each key is protected either in TPM or encrypted by a key protected by TMP. Each key has flag (non-migratable or migratable). The leaves are protected secrets/data and the intermediate nodes are the storage and identity keys