Random number generation

Question 1

When are random number generators used (give 4)

Answer 1

• Gaming
• Gambling
• Creating user IDS
• Jurors
• Simulation of complex systems
• Research experiments
• Statistical sampling
• Crypography

Question 2

What are random numbers?

Answer 2

• A random number is a number chosen by chance
• They are drawn using random sampling techniques from a set of permissible numbers
• Each number drawn must be statistically independent of each

Question 3

computing random numbers

Answer 3

There are 2 approaches:
- Pseudo-Random number generators
- True random number generators

Question 4

Pseudo random number generators (PNRGs)

Answer 4

PRNGs use mathematical formulae or precalculated tables to produce sequences of numbers that appear
random.

Question 5

PNRG characteristics

Answer 5

*Efficiency – can produce many numbers in a short space of time.
*Deterministic - a given sequence of numbers can be reproduced at a later date if the starting point in the sequence is known.
*Periodic - a sequence of numbers will eventually repeat itself.

Question 6

True random number generators (TRNGs)

Answer 6

*Numbers generated by TRNGs can be considered truly random.
*TRNGs extract randomness from physical phenomena and introduce it into the computing platform.

Question 7

TRNG charateristics

Answer 7

• Inefficiency –can take some time to produce numbers
• Nondeterministic -a given sequence of numbers cannot be reproduced, although the same sequence may occur several times by chance.
• Aperiodic –a sequence of numbers will not repeat itself, unless by chance.

Question 8

PNRG Disadvantages

Answer 8

1. True random numbers are difficult to obtain.
2. Programs using random numbers are difficult to debug, especially when using a TRNG.
3. Sequences of random numbers eventually repeat themselves (when using a PRNG).

Question 9

Why are pseudo-random numbers a security problem?

Answer 9

• Cryptographic keys are generated using random number generators.
• But, pseudo-random numbers are deterministic meaning any sequence of pseudorandom numbers can be reproduced anytime.
• This means cryptographic keys can be reproduced!
• Cryptography can be broken! Data can be decrypted!

Question 10

secure random numbers

Answer 10

A pseudo random number generator that is suitable for cryptographic usage is called a Cryptographically Secure
Pseudo-Random Number Generator (CSPRNG).

Question 11

What properties does the CSPRNG exhibit

Answer 11

1. It appears random.
2. Its value is unpredictable in advance.
3. It cannot be reliably reproduced after generation.