/*
Package serial provides serial number related functionality.
*/
package serial

import (
	"crypto/rand"
	"io"
	"math/big"
)

const randBits = 160

// Rand returns a random serial number with 159 bits of entropy.
func Rand() *big.Int {
	q := make([]byte, randBits/8)
	io.ReadFull(rand.Reader, q)
	// this just means all serial numbers are justified to the same bitlen, which is nice for tools!
	q[0] |= 0x80
	return big.NewInt(0).SetBytes(q)
}