Cryptographic Hash Algorithms Flashcards
What is a hash function?
One-way hash function that requires collision resistance
MD5
- no effective collision resistance
- produces 128-bit hash
SHA-1 Function
- Based on MD5
- Produces 160-bit hash
SHA-2
- use if collision resistance is required
What is collision resistance?
When it is hard to find two inputs that hash into the same output
SHA-3
New hash algorithm standardised by NIST
Weakened or compromised hash functions?
1) MD5 suffered collision attack
2) SHA-1 vulnerable
Digital signatures
- 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
Cryptographic Signature
- Hash made of message
- Fixed length digest unique to message
Collision attacks on MD5 & SHA-1
MD5: PlayStation attack on public keys
SHA-1: Created two PDF files with same signature
Message Authentication Codes
- an authenticate tag for a message
- apply authentication scheme and secret key to message
Blockchain
- combines elements of BitTorrent peer-to-peer sharing and cryptographic technology
Bitcoin
Global cryptocurrency and digital payment system