Cryptographic Hash Algorithms

Question 1

What is a hash function?

Answer 1

One-way hash function that requires collision resistance

Question 2

MD5

Answer 2

• no effective collision resistance

- produces 128-bit hash

Question 3

SHA-1 Function

Answer 3

• Based on MD5

- Produces 160-bit hash

Question 4

SHA-2

Answer 4

• use if collision resistance is required

Question 5

What is collision resistance?

Answer 5

When it is hard to find two inputs that hash into the same output

Question 6

SHA-3

Answer 6

New hash algorithm standardised by NIST

Question 7

Weakened or compromised hash functions?

Answer 7

1) MD5 suffered collision attack

2) SHA-1 vulnerable

Question 8

Digital signatures

Answer 8

• used to confirm identity of sender

1) signature generated from message and private key should verify authenticity with public key
2) infeasible to generate signature without private key

Question 9

Cryptographic Signature

Answer 9

• Hash made of message

- Fixed length digest unique to message

Question 10

Collision attacks on MD5 & SHA-1

Answer 10

MD5: PlayStation attack on public keys

SHA-1: Created two PDF files with same signature

Question 11

Message Authentication Codes

Answer 11

• an authenticate tag for a message

- apply authentication scheme and secret key to message

Question 12

Blockchain

Answer 12

• combines elements of BitTorrent peer-to-peer sharing and cryptographic technology

Question 13

Bitcoin

Answer 13

Global cryptocurrency and digital payment system