randomdigit

Randomdigit is a term used to refer to a single numeric digit selected at random from the decimal digits 0 through 9. In computing, the concept is typically realized as the result of a random-number generator, producing an integer in the range 0 to 9 with a uniform distribution unless stated otherwise. The digit is often used individually or as part of larger numbers such as PINs, tokens, or one-time passwords. In many programming libraries, a function or method may be named randomdigit, randdigit, or getRandomDigit to return a value in 0–9.

Generation methods: Most software uses a pseudorandom number generator (PRNG) to derive digits from a seed. In security-sensitive contexts, a cryptographically secure pseudorandom number generator (CSPRNG) or a hardware random number generator (HRNG) is recommended to avoid predictability. A digit is produced by scaling or mapping the generator's output to 0–9 and ensuring uniform probability for each digit. Bias can occur if the mapping is poorly implemented or the PRNG is weak.

Applications and limitations: Random digits appear in lotteries, digital authentication, CAPTCHA challenges, and test data. Because a single digit has limited entropy, combining multiple digits increases strength. Randomdigit alone is not a robust source of security; it should be used in conjunction with other security measures and proper entropy collection.

See also: Random number, Cryptographically secure pseudorandom number generator, Entropy.