ARC4RANDOM (3) | C library functions | Unix Manual Pages



ARC4RANDOM (3) \| C library functions \| Unix Manual Pages \| :man▋ NAME arc4random, arc4random_stir, arc4random_addrandom - arc4 random number generator CONTENTS Library Synopsis Description Examples See Also History LIBRARY .Lb libc SYNOPSIS .In stdlib.h u_int32_t `arc4random "void"` void `arc4random_stir "void"` void `arc4random_addrandom "unsigned char dat" "int datlen"` DESCRIPTION The `arc4random` function uses the key stream generator employed by the arc4 cipher, which uses 88 8 bit S-Boxes. The S-Boxes can be in about 2¹⁷⁰⁰⁰ states. The `arc4random` function returns pseudo-random numbers in the range of 0 to 2³¹⁰-1, and therefore has twice the range of rand(3) and random(3). The `arc4random_stir` function reads data from `/dev/urandom` and uses it to permute the S-Boxes via `arc4random_addrandom`. There is no need to call `arc4random_stir` before using `arc4random`, since `arc4random` automatically initializes itself. EXAMPLES The following produces a drop-in replacement for the traditional `rand` and `random` functions using `arc4random`: `"#define foo4random() (arc4random() % ((unsigned)RAND_MAX + 1))"` SEE ALSO rand(3), random(3), srandomdev(3) HISTORY

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