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)
  0a 10 91 01 64 e4 39 ff e4 0b

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

as.numeric(rnd)
   10  16 145   1 100 228  57 255 228  11

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

x <- rand_bytes(1)
as.logical(rawToBits(x))
  TRUE FALSE  TRUE FALSE FALSE FALSE  TRUE  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)
  0.51264049 0.26298265 0.52894224 0.45853923 0.91369995 0.06634984
 0.34697549 0.77925962 0.32352883 0.36852364

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)) 