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Random Number Generator

Definition: A Random Number Generator (RNG) is an algorithm or device designed to produce a sequence of numbers that do not display any distinguishable patterns in their appearance or generation. This randomness is crucial for various applications, including cryptography, simulations, and statistical sampling.

In cyber security, RNGs are particularly important in areas such as cryptographic key generation, where the strength of encryption often depends on the unpredictability of the keys used. A secure RNG ensures that cryptographic keys cannot be easily guessed or determined by attackers, thus maintaining the integrity and confidentiality of encrypted data.

There are two main types of RNGs: Pseudorandom Number Generators (PRNGs), which use algorithms to produce long sequences of apparently random results from an initial value known as a seed, and True Random Number Generators (TRNGs), which generate randomness from physical processes, often leveraging quantum properties or thermal noise, and do not require a seed.

Key Characteristics:

  • Unpredictability: True randomness means the next number in the sequence should be unpredictable based on the preceding numbers.
  • Lack of Patterns: A good RNG does not produce discernible patterns or repetition.
  • Reproducibility: PRNGs can be reproduced if the initial seed value is known, which is useful for testing and simulation purposes.
  • Statistical Randomness: RNGs are designed to pass various tests that measure their statistical randomness.


  • Real-World Example: Secure online banking transactions often use cryptographic keys generated by RNGs to ensure that each session is unique and secure.
  • Hypothetical Scenario: An online casino uses an RNG to determine the outcome of roulette wheel spins to ensure that results are fair and unpredictable.

Related Terms:

  • Cryptography: The practice and study of techniques for secure communication in the presence of third parties.
  • Pseudorandom Number Generator (PRNG): An algorithm for generating a sequence of numbers whose properties approximate the properties of sequences of random numbers.
  • True Random Number Generator (TRNG): A system that generates random numbers from a physical process, rather than a set algorithm.

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