Generating Secure Random Numbers in R

2025-05-29

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] 42 5d 1f 0f 67 25 2a 31 4c dd

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

as.numeric(rnd)

 [1]  66  93  31  15 103  37  42  49  76 221

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

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

[1] FALSE FALSE FALSE  TRUE  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] 0.06573898 0.05744893 0.07027785 0.35537347 0.38368318 0.85845230
 [7] 0.74989455 0.40095473 0.08655456 0.64735050

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))