Generating Secure Random Numbers in R

2026-05-11

The rand_bytes function binds to RAND_bytes in OpenSSL to generate cryptographically strong pseudo-random bytes. See the OpenSSL documentation for what this means.

rnd <- rand_bytes(10)
print(rnd)

 [1] a6 8c c1 20 be 93 a8 b5 94 60

Bytes are 8 bit and hence can have 2^8 = 256 possible values.

as.numeric(rnd)

 [1] 166 140 193  32 190 147 168 181 148  96

Each random byte can be decomposed into 8 random bits (booleans)

x <- rand_bytes(1)
as.logical(rawToBits(x))

[1] FALSE FALSE  TRUE FALSE  TRUE  TRUE FALSE  TRUE

Secure Random Numbers

rand_num is a simple (2 lines) wrapper to rand_bytes to generate random numbers (doubles) between 0 and 1.

rand_num(10)

 [1] 0.04316432 0.48814261 0.66936772 0.92401574 0.01119552 0.22245049
 [7] 0.63153863 0.67676466 0.95435889 0.85379763

To map random draws from [0,1] into a probability density, we can use a Cumulative Distribution Function. For example we can combine qnorm and rand_num to simulate rnorm:

# Secure rnorm
x <- qnorm(rand_num(1000), mean = 100, sd = 15)
hist(x)

Same for discrete distributions:

# Secure rbinom
y <- qbinom(rand_num(1000), size = 20, prob = 0.1)
hist(y, breaks = -.5:(max(y)+1))