Lecture 5

Question 1

What’s AEAD?

Answer 1

Authenticated Encryption with Associated Data: Associated extra data that should not be encrypted e.g. the IP-address when sending network packets

Question 2

What is the main cherished feature of Authenticated Encryption?

Answer 2

When used, we know that the message we receive, is guaranteed to be the one meant for us. We know that when AE is used, the message is unforgeable (unchangeable).

Question 3

What’s OCB?

Answer 3

Rullpapper (RIZZLA)

Question 4

What’s the pros and cons with CCM vs. OCB?

Answer 4

CCM: No patent issues but slow
OCB: Patent issues but fast

Question 5

What to look for in crypto libraries? Kanske onödig?

Answer 5

High level API
Fast, safe with modern language
Backed and used by big players

Question 6

What will quantum computers be able to break?

Answer 6

Asymmetric encryption but not symmetric encryption

Question 7

What’s Shors’ algorithm, connected to quantum computers?

Answer 7

Quantum algorithm to find the prime of big integers. Makes the “hard problem” easy to solve. The hard problem that lay the ground of EC, RSA, DH.

Question 8

What’s Grovers’ algorithm, connected to quantum computers?

Answer 8

Faster brute-force. It’s difficult to implement in practice.

Question 9

What’s one community goal for the Post quantum crypto world?

Answer 9

Design new primitives (longer key-lengths etc.) to counter the power of QC. Tradeoffs are that all will be longer (keys, ciphertexts …)

Question 10

What’s the new Diffie-Hellman?

Answer 10

KYBER (KOLLA MER)

Question 11

What are the basic goals of TLS (Transport Layer Security)?

Answer 11

Secrecy (encryption), Integrity (MACs) and server and optional client Authentication (signatures)

Question 12

When should you use authenticated encryption?

Answer 12

Always

Question 13

There are two related security notions for symmetric encryption, what are these two? Each of them is the “Integrity of ____”, of what?

Answer 13

INT-PTXT: Integrity of plaintext
INT-CTXT: Integrity of ciphertext

Question 14

Mention 3 or more general cryptographic libraries

Answer 14

OpenSSL
LibreSSL
BoringSSL
GnuTLS
BouncyCastle

Question 15

Mention 2 or more modern libraries (that should be used):

Answer 15

Libsodium
NaCl
Tink

Question 16

What is TLS?

Answer 16

TLS, or Transport Layer Security, is a protocol that ensures secure communication over a computer network, such as the internet. It’s a way to protect the data that is being transmitted between two systems from being intercepted or tampered with by unauthorized parties.

Also, the “S” in HTTPS

Question 17

Is TLS used today?

Answer 17

Yes, widely. It’s considered the new default.

Question 18

Should we always use Authenticated Encryption?

Answer 18

Yes, when possible.

Question 19

Should we always use libraries like libsodium or Tink?

Answer 19

Yes, when possible.

Question 20

Should we always use libraries like OpenSSL or LibreSSL?

Answer 20

No, use modern libraries if possible.