From 7a573754380f076cb5db7d842ef72ef7858bcafe Mon Sep 17 00:00:00 2001
From: akwizgran <akwizgran@users.sourceforge.net>
Date: Sat, 28 Dec 2013 13:44:26 +0000
Subject: [PATCH] Interleave samples to get a better estimate of PBKDF2 running
time.
---
.../sf/briar/crypto/CryptoComponentImpl.java | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/briar-core/src/net/sf/briar/crypto/CryptoComponentImpl.java b/briar-core/src/net/sf/briar/crypto/CryptoComponentImpl.java
index 566aec70b2..9b449b7a5e 100644
--- a/briar-core/src/net/sf/briar/crypto/CryptoComponentImpl.java
+++ b/briar-core/src/net/sf/briar/crypto/CryptoComponentImpl.java
@@ -61,6 +61,7 @@ class CryptoComponentImpl implements CryptoComponent {
private static final int STORAGE_IV_BYTES = 16; // 128 bits
private static final int PBKDF_SALT_BYTES = 16; // 128 bits
private static final int PBKDF_TARGET_MILLIS = 500;
+ private static final int PBKDF_SAMPLES = 30;
// Labels for secret derivation
private static final byte[] MASTER = { 'M', 'A', 'S', 'T', 'E', 'R', '\0' };
@@ -463,18 +464,19 @@ class CryptoComponentImpl implements CryptoComponent {
// Package access for testing
int chooseIterationCount(int targetMillis) {
- List<Long> quickSamples = new ArrayList<Long>();
- List<Long> slowSamples = new ArrayList<Long>();
+ List<Long> quickSamples = new ArrayList<Long>(PBKDF_SAMPLES);
+ List<Long> slowSamples = new ArrayList<Long>(PBKDF_SAMPLES);
long iterationNanos = 0, initNanos = 0;
while(iterationNanos <= 0 || initNanos <= 0) {
- // Take ten samples of the running time with one iteration
- for(int i = 0; i < 10; i++) quickSamples.add(sampleRunningTime(1));
- // Take ten samples of the running time with eleven iterations
- for(int i = 0; i < 10; i++) slowSamples.add(sampleRunningTime(11));
+ // Sample the running time with one iteration and two iterations
+ for(int i = 0; i < PBKDF_SAMPLES; i++) {
+ quickSamples.add(sampleRunningTime(1));
+ slowSamples.add(sampleRunningTime(2));
+ }
// Calculate the iteration time and the initialisation time
long quickMedian = median(quickSamples);
long slowMedian = median(slowSamples);
- iterationNanos = (slowMedian - quickMedian) / 10;
+ iterationNanos = slowMedian - quickMedian;
initNanos = quickMedian - iterationNanos;
if(LOG.isLoggable(INFO)) {
LOG.info("Init: " + initNanos + ", iteration: "
@@ -483,7 +485,7 @@ class CryptoComponentImpl implements CryptoComponent {
}
long targetNanos = targetMillis * 1000L * 1000L;
long iterations = (targetNanos - initNanos) / iterationNanos;
- if(LOG.isLoggable(INFO)) LOG.info("Raw iterations: " + iterations);
+ if(LOG.isLoggable(INFO)) LOG.info("Target iterations: " + iterations);
if(iterations < 1) return 1;
if(iterations > Integer.MAX_VALUE) return Integer.MAX_VALUE;
return (int) iterations;
--
GitLab