97 lines
2.4 KiB
Go
97 lines
2.4 KiB
Go
// Copyright (C) 2016 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this file,
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// You can obtain one at https://mozilla.org/MPL/2.0/.
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package rand
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import "testing"
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func TestSecureSource(t *testing.T) {
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// This is not a test to verify that the random numbers are secure,
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// merely that the numbers look random at all and that we've haven't
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// broken the implementation by masking off half the bits or always
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// returning "4" (chosen by fair dice roll),
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const nsamples = 10000
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// Create a new source and sample values from it.
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s := newSecureSource()
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res0 := make([]int64, nsamples)
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for i := range res0 {
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res0[i] = s.Int63()
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}
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// Do it again
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s = newSecureSource()
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res1 := make([]int64, nsamples)
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for i := range res1 {
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res1[i] = s.Int63()
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}
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// There should (statistically speaking) be no repetition of the values,
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// neither within the samples from a source nor between sources.
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for _, v0 := range res0 {
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for _, v1 := range res1 {
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if v0 == v1 {
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t.Errorf("Suspicious coincidence, %d repeated between res0/res1", v0)
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}
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}
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}
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for i, v0 := range res0 {
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for _, v1 := range res0[i+1:] {
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if v0 == v1 {
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t.Errorf("Suspicious coincidence, %d repeated within res0", v0)
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}
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}
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}
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for i, v0 := range res1 {
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for _, v1 := range res1[i+1:] {
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if v0 == v1 {
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t.Errorf("Suspicious coincidence, %d repeated within res1", v0)
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}
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}
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}
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// Count how many times each bit was set. On average each bit ought to
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// be set in half of the samples, except the topmost bit which must
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// never be set (int63). We raise an alarm if a single bit is set in
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// fewer than 1/3 of the samples or more often than 2/3 of the samples.
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var bits [64]int
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for _, v := range res0 {
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for i := range bits {
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if v&1 == 1 {
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bits[i]++
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}
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v >>= 1
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}
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}
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for bit, count := range bits {
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switch bit {
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case 63:
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// The topmost bit is never set
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if count != 0 {
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t.Errorf("The topmost bit was set %d times in %d samples (should be 0)", count, nsamples)
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}
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default:
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if count < nsamples/3 {
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t.Errorf("Bit %d was set only %d times out of %d", bit, count, nsamples)
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}
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if count > nsamples/3*2 {
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t.Errorf("Bit %d was set fully %d times out of %d", bit, count, nsamples)
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}
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}
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}
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}
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var sink int64
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func BenchmarkSecureSource(b *testing.B) {
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s := newSecureSource()
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for i := 0; i < b.N; i++ {
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sink = s.Int63()
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}
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b.ReportAllocs()
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}
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