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// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package rand implements a cryptographically secure
// random number generator.
package rand
import "io"
// Reader is a global, shared instance of a cryptographically
// secure random number generator.
// On Linux and FreeBSD, Reader uses getrandom(2) if available, /dev/urandom otherwise.
// On OpenBSD, Reader uses getentropy(2).
// On other Unix-like systems, Reader reads from /dev/urandom.
// On Windows systems, Reader uses the CryptGenRandom API.
// On Wasm, Reader uses the Web Crypto API.
var Reader io.Reader
// Read is a helper function that calls Reader.Read using io.ReadFull.
// On return, n == len(b) if and only if err == nil.
func Read(b []byte) (n int, err error) {
return io.ReadFull(Reader, b)
func warnBlocked() {
println("crypto/rand: blocked for 60 seconds waiting to read random data from the kernel")