Crypto U8 (part 1), Randomness

jjanesko
Mind Map by , created over 6 years ago

IYM002 (Unit 8 - randomness, freshness, AKE) Mind Map on Crypto U8 (part 1), Randomness, created by jjanesko on 04/22/2013.

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jjanesko
Created by jjanesko over 6 years ago
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Crypto U8 (part 1), Randomness
1 meaning
1.1 uncertainty
1.2 unpredictability
1.3 have no relation to previous chosen numbers
1.4 have no obvious structure
2 randomn values in cryptography
2.1 salt
2.1.1 random data that are used as an additional input to a one-way function that hashes a password or passphrase.
2.1.1.1 ex. Unix password file
2.2 IVs (initialization vector)
2.2.1 a fixed-size input to a cryptographic primitive that is typically required to be random or pseudorandom.
2.2.1.1 ex. cipher block chaining mode
2.3 values used for freshness checks in cryptographic protocols
2.3.1 nonce = number used only once
2.3.1.1 sender sends randomly generated nonce to receiver, receiver sends nonce back with reply to show reply belongs to the original message
2.4 random numbers used to generate symmetric keys
2.4.1 random process are used to generate keys
2.4.1.1 non-deterministic is better than pseudorandom for master keys
2.5 somehow required in El Gamal, but don't understand why
3 What should seem random?
3.1 keystreams
3.2 hash codes
3.3 ciphertexts
4 generating random numbers
4.1 non-deterministic
4.1.1 advantages and disadvantages
4.1.1.1 expensive
4.1.1.2 completely random
4.1.1.3 cannot replicate in another location (so tough to synchronize)
4.1.2 based on randomess proced by physical phenomena
4.1.2.1 hardware
4.1.2.1.1 measurement of white noise from electrical appliances
4.1.2.1.2 quantum measurement of a photon reflected in a mirror
4.1.2.2 software
4.1.2.2.1 keystroke captures
4.1.2.2.2 hard drive seek times
4.2 deterministic (pseudorandom)
4.2.1 how does it work?
4.2.1.1 takes a seed value and outputs a string of bits with no apparent structure
4.2.1.2 2 parts
4.2.1.2.1 seed
4.2.1.2.1.1 should be different every time & not guessable
4.2.1.2.1.2 usually short
4.2.1.2.1.3 usually a "standard" length (like 128 bits)
4.2.1.2.2 generator
4.2.1.2.2.1 use standard, well known ones (nothing home made)
4.2.2 advantages and disadvantages
4.2.2.1 cheap to implement
4.2.2.2 two identical outputs can be generated in 2 different locations (synchronizable)
4.2.2.3 have to find way to distribute seed

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