Tilviljunarkenndir

Tilviljunarkenndir are mechanisms that generate sequences of numbers that are intended to appear random. They are used in statistics, computer simulations, gaming, and cryptography to produce unpredictable values or to seed other processes.

They fall into two broad categories: true random number generators (TRNGs), which derive randomness from physical processes whose outcomes are inherently unpredictable (such as electronic noise, radioactive decay, or atmospheric phenomena); and pseudo-random number generators (PRNGs), which use deterministic algorithms to produce long sequences that only approximate randomness. PRNGs require a starting value, or seed, and their sequences repeat after a period.

Cryptographically secure tilviljunarkenndir (CSPRNGs) are a subset of PRNGs designed to limit predictability even if part of the internal state is known. They are used in security-sensitive contexts and follow standards and design practices to resist attacks. Common practical examples include hash- and stream-based generators and DRBGs such as CTR-DRBG and HMAC-DRBG, as defined by guidelines like NIST SP 800-90.

Key properties include uniform distribution, independence, and long period for PRNGs, and high entropy for TRNGs. The quality of a tilviljunarkennd depends on its statistical behavior and unpredictability, which are assessed using tests such as DIEHARD, NIST test suites, and empirical usage checks.

Applications span Monte Carlo simulations, statistical sampling, gaming, and cryptography. In practice, TRNGs are often used to seed PRNGs to combine the benefits of both approaches, while system sources such as /dev/random or cryptographic DRBGs are used in security contexts.