std/os/entropy
std/os/src/entropy.trb
Entropy: bytes of the operating system's source of randomness, which is fit for cryptography - what a key, a nonce,
a token and the seed of a generator are made from (docs/design/RANDOM.md).
It is a module of its own and a capability of its own, entropy, because it reads nothing about the machine: its
import says "this file makes values nobody can predict", so a package that makes a nonce is reported as touching
entropy and not the whole operating system, and a sandboxed script is granted it with modules "std/os/entropy".
type Entropy
type EntropyThe operating system's source of randomness: BCryptGenRandom on Windows, getrandom on Linux and FreeBSD,
getentropy on macOS, and crypto.getRandomValues in the browser. Every byte is as unpredictable as the system can
make it, so what it answers may be a key; nothing seeds it and nothing repeats it.
A seeded generator - the same numbers from the same seed, for a test or a simulation - is a different thing and a
value of its own, so that one is never mistaken for the other: this is where its seed comes from
(Entropy.int64), and never what it is.
Examples
const nonce = Entropy.bytes 18
print nonce.length()
Panics
Where the operating system does not answer, which none of the systems above does once it has started: there is no
safe way on without randomness, and a failure a caller could handle would invite a weaker source in its place. Go
decided the same for crypto/rand (1.24).
Related
Entropy.bytes- the bytes.Entropy.int64- eight of them as a number, the seed of a generator.
fn bytes
static fn bytes(count: Int): Bytescount bytes of the system's source of randomness: Entropy.bytes 16 for a nonce, 32 for a key of 256 bits.
Examples
const key = Entropy.bytes 32
print(key.length() == 32)
Panics
Where count is negative, and where the operating system does not answer.
fn int64
static fn int64(): Int64Eight bytes of the system's source of randomness as one Int64, every one of its 64 bits random, negative as often
as not: the unpredictable seed of a generator.
Examples
const seed = Entropy.int64()
print "seeded with {seed}"