Random Number Generator

Random Number and Random Number Generator

Random Number


A random number is a number generated by a process, whose outcome is unpredictable and does not follow any pattern. These numbers are essential in statistics, gambling, computer simulations, cryptography, and other areas where an unpredictable outcome is desired.

Types of Random Numbers

  • True Random Numbers: Generated using physical processes, such as atmospheric noise, thermal noise, or other quantum phenomena. Inherently unpredictable.
  • Pseudo-Random Numbers: Generated using algorithms and are not truly random, but approximate randomness closely enough for most purposes. They require a seed value and produce a deterministic sequence of numbers.

Random Number Generator (RNG)


An RNG is a device or algorithm designed to produce random numbers. The quality of randomness required varies depending on the use case, with higher standards in security and cryptography applications.

Types of RNGs

  • Hardware RNGs: Use physical phenomena to generate true random numbers. Common in high-security applications.
  • Pseudo-Random Number Generators (PRNGs): Algorithm-based and widely used in computing. Good PRNGs are fast and produce a long sequence of numbers with a distribution that appears random.


Cryptography, simulations and modeling, gaming and gambling, and statistical sampling are some of the key applications of RNGs.

Characteristics of Good RNGs

Uniformity, independence, and reproducibility (for PRNGs) are crucial characteristics of good RNGs.

Security Considerations

In cryptography, the predictability of a PRNG can lead to security vulnerabilities. Therefore, cryptographically secure PRNGs (CSPRNGs) are required, which are designed to withstand attacks.

Common Algorithms

Linear Congruential Generators (LCGs), Mersenne Twister, and Cryptographically Secure PRNGs are some of the commonly used algorithms in RNGs.

Limitations and Challenges

PRNGs eventually repeat their number sequence and are vulnerable to reverse engineering. Ensuring true randomness in hardware RNGs can be challenging due to biases and environmental influences.

In summary, random numbers and random number generators are crucial in many fields, providing unpredictability and variety necessary for simulations, secure communications, and statistical analysis. Understanding the different types of RNGs, their applications, and limitations is key in choosing the right approach for a given task, especially in areas where security and fairness are paramount.