Generating Secure Random Numbers in R

2026-06-22

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] 6a 73 06 fa 8e f4 ef 75 0b 48

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

as.numeric(rnd)

 [1] 106 115   6 250 142 244 239 117  11  72

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

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

[1] FALSE  TRUE FALSE  TRUE FALSE FALSE FALSE FALSE

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] 0.2619525 0.4141895 0.3887287 0.3469057 0.1518118 0.0504941 0.6350635
 [8] 0.3632766 0.4756416 0.8981217

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))