// This is sufficient on Linux, OS X, and FreeBSD.
```
For OS X that would use 160-bit Yarrow PRNG based on SHA-1 key,
for FreeBSD - 256-bit Yarrow algorithm. For both operating systems /dev/random and
/dev/urandom are equal.
2.[in Linux](http://golang.org/src/crypto/rand/rand_linux.go#L22) it falls back
to urandom in several cases:
```
// Test whether we should use the system call or /dev/urandom.
// We'll fall back to urandom if:
// - the kernel is too old (before 3.17)
// - the machine has no entropy available (early boot + no hardware
// entropy source?) and we want to avoid blocking later.
```
The first clause would be used for several production-class operationg systems.
1.[in UNIX-like](http://golang.org/src/crypto/rand/rand_unix.go) operating system it uses /dev/urandom device:
```
// Easy implementation: read from /dev/urandom.
// This is sufficient on Linux, OS X, and FreeBSD.
```
For OS X that would use 160-bit Yarrow PRNG based on SHA-1 key, for FreeBSD - 256-bit Yarrow algorithm. For both operating systems /dev/random and /dev/urandom are equal.
2.[in Linux](http://golang.org/src/crypto/rand/rand_linux.go#L22) it falls back to urandom in several cases:
```
// Test whether we should use the system call or /dev/urandom.
// We'll fall back to urandom if:
// - the kernel is too old (before 3.17)
// - the machine has no entropy available (early boot + no hardware
// entropy source?) and we want to avoid blocking later.
```
The first clause would be used for several production-class operationg systems.
3.[in Windows]() it uses Windows CryptGenRandom API.
According to [wikipedia](https://en.wikipedia.org/?title=/dev/random) using
/dev/urandom instead of /dev/random seems to be safe.
According to [wikipedia](https://en.wikipedia.org/?title=/dev/random) using /dev/urandom instead of /dev/random seems to be safe.
