Initial commit of pkg functions

pkg/serial/rand.go

@@ -0,0 +1,21 @@
+/*
+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)
+}