Random String

random.go

/*

 Sources of randomness from the environment include inter-keyboard
 timings, inter-interrupt timings from some interrupts, and other
 events which are both non-deterministic and hard for an
 outside observer to measure.  Randomness from these sources are
 added to an entropy pool, which is mixed using a CRC-like function.
 As random bytes are mixed into the entropy pool, the routines keep
 an estimate of how many bits of randomness have been stored into
 the random number generator internal state.

*/

package main

import (
	"fmt"
	"math/rand"
	"os/exec"
	"strconv"
)

const (
	Alphabet     = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
	Numerals     = "1234567890"
	specialChars = "~!@#$%^&*()-_+={}[]\\|<,>.?/\"';:`"
)

var (
	//Seed function to initialize the default Source if different behavior is required for each run.
	seededRand *rand.Rand = rand.New(rand.NewSource(getCPUNoise()))
	pool                  = Alphabet + Numerals + specialChars
)

// Gather interrupts and CPU context switches from vmstat
func getCPUNoise() int64 {
	cmd := "vmstat -s | egrep '(interrupts| CPU context switches)' | awk '{print $1}'| xargs | tr -d ' \n'"
	out, err := exec.Command("bash", "-c", cmd).Output()
	if err != nil {
		panic(err)
	}
	str2 := string(out)
	randomDigit, err := strconv.ParseInt(str2, 10, 64)
	return randomDigit
}

// Generate a random string of A-Z chars with len = l
func randomString(l int) string {
	bytes := make([]byte, l)
	for i := 0; i < l; i++ {
		bytes[i] = pool[seededRand.Intn(len(pool))]
	}
	return string(bytes)
}

func main() {
	fmt.Println(randomString(64))
}