Cryptographically strong random bytes

Returns n random bytes that are suitable for keys, salts and nonces. Use it whenever a value must be unguessable; use set.seed() and runif() for simulations, where reproducibility is the point.

Usage

rndbytes(n)

Arguments

n

Whole number from 1 to 1048576: the number of bytes.

Value

A raw vector of length n. Print it as hex with paste(format(x), collapse = "").

Details

Reads the operating system's own random source rather than R's Mersenne Twister: /dev/urandom on Unix and macOS, RtlGenRandom on Windows.

This distinction matters for anything that becomes a key. set.seed() makes R's generator reproducible BY DESIGN, and its state can be recovered from its output; a key drawn from it is guessable. Reading the OS source also leaves R's own random stream untouched, so generating a key does not perturb a reproducible analysis.

If no OS source can be read the function FAILS rather than falling back to a weaker generator, because a silent downgrade in a key is worse than an error.

Errors: n not a single whole number from 1 to 1,048,576 (1 MiB); no readable operating-system source.

See also

drvkey() to stretch a passphrase instead, pqckg() which uses this for its seeds.

Examples

rndbytes(8)
#> [1] 49 12 44 ce 9d dd b4 fb

# Independent between calls, unlike a seeded generator.
identical(rndbytes(16), rndbytes(16))
#> [1] FALSE

# R's own stream is not consumed, so a seeded analysis is unaffected.
set.seed(1)
a <- stats::runif(1)
set.seed(1)
invisible(rndbytes(32))
identical(stats::runif(1), a)
#> [1] TRUE

# As hex, for a seed argument.
paste(format(rndbytes(4)), collapse = "")
#> [1] "2dabc30f"

try(rndbytes(0))
#> Error : `n` must be a single integer between 1 and 1048576