1 - Intro Flashcards
Cryptography uses
E commerce, transactions.
Authentication, data integrity, signatures, non-repudiation
Cryptography idea
“Secret communication”
Cryptanalysis
“Code Breaking”
Passive attacks
Listening in/Interception (classical attack)
Traffic analysis
Active attacks
Message tampering
Replay attacks (send message again)
Impersonation
Man in the middle attack
Confidentiality
Message can only be read by intended recipient
Authentication
Guarantees identity
Integrity
Unauthorised changes to message detected
Non-repudiation
Party cannot DENY that a message was sent/received by them
Why use a key?
You do not need to redesign the algorithm every time it is compromised when communicating with several different people.
Different people, different keys.
Should you assume the algorithm is secret?
No, “The algorithms should be assumed to be publicly known” (kerckhoff’s principle)A
Advantages of public algorithms
Weak algorithims discarded
Strong algorithms improve
Protocol standards
Less likely to have backdoors
Symmetric Cryptography
Both parties use the same key.
Issue: Have to share key
If Symmetric key is transferred over secure channel, why would you not just communicate overall using that channel?
Expensive,
Channel may not be permanent
Public-key cryptography
How does it work
Each party has a private and public key.
Others encrypt using recipients public key. Only recipients private key can decrypt.
