Week 4 Flashcards
What is Cryptography?
The science of secret writing
What is Cryptanalysis?
The science of code-breaking
What is a cipher?
An algorithm that changes plain text to cipher text. This process is called encryption.
If the key range is small the cipher is not…..enough (fill in the blanks)
Stringent
What is Kerckhoff’s Principle?
The principle that only keys are secret and everything else is public
What is secret key cryptography? (symmetric key)
Same key for encryption and decryption (to be kept secret)
What is public key cryptography? (asymmetric key)
Provides a public key and a private key for each party
List 3 properties of public and private keys
1- Easy to generate
2- Easy to encrypt knowing the public key
3- Easy to decrypt knowing the private key
What are Hybrid systems?
First, the two parties use an asymmetric cipher to negotiate a session key then, encrypt the conversation using the session key as a secret key of a symmetric cipher.
What are the two types of attacks on ciphers?
- Brute force
- Cryptanalysis
What is a Brute force attack?
One that where the attacker tries all possible keys one by one.
What is substitution?
Replace characters of plaintext with other characters
What is transposition?
Rearranging the order of plaintext characters
What is steganography?
Concealing existence of a message (its not secure though) e.g. behind images
What is a Unconditionally secure cipher?
One where the ciphertext does not contain enough
information to determine uniquely the plaintext (impossible to break)
