Week 2 - Randomness + One-Time Pads Flashcards
what is true Randomness?
numbers have no discernible patterns and each event is equally probable
Examples of True Randomness?
- coin flip
- national lottery
- lava lamp movements
: What is a pseudo-random number generator?
an algorithm that produces a series of random numbers based on an initial seed
what is a seed in PRNG?
an initial value that is kept secret + used to reproduce the sequence
What is a Cryptographically Secure Pseudo-Random Number Generator (CSPRNG)?
a type of PRNG that is indistinguishable from true randomness + secure against attacks
Why are CSPRNGs used in cryptography?
they are efficient and useful when sequences need to be replicated securely
or
produce random numbers that are unpredictable and resistant to cryptanalysis
what is a one time pad (OTP)?
an encryption method where a truly random key is used to encrypt a message
what are the four requirements for an OTP?
- key is truly random
- only two copies exist, (encryption and decryption).
- key is used once and destroyed after use
- key must be as long as message
What is “perfect secrecy”?
when OTP is correctly implemented and is unbreakable regardless of computational power
What are the practical challenges of OTP?
generating long random keys + securely sharing them is difficult
What is the middle square method?
an early version of PRNG where the seed is squared, middle digits are extracted and the process is repeated
How does a one-time pad encrypt and decrypt messages?
each character in the message is combined with a corresponding character from the random key
