From 204711e5dbebf6f5c216ae2599fbac3119fe18c3 Mon Sep 17 00:00:00 2001
From: akwizgran <michael@briarproject.org>
Date: Fri, 19 Jan 2018 10:58:45 +0000
Subject: [PATCH] Reduce minimum scrypt cost for low-end devices.
---
.../org/briarproject/bramble/crypto/ScryptKdf.java | 2 +-
.../org/briarproject/bramble/crypto/ScryptKdfTest.java | 10 ++++++++++
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/bramble-core/src/main/java/org/briarproject/bramble/crypto/ScryptKdf.java b/bramble-core/src/main/java/org/briarproject/bramble/crypto/ScryptKdf.java
index b5cec69061..b3e567323a 100644
--- a/bramble-core/src/main/java/org/briarproject/bramble/crypto/ScryptKdf.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/crypto/ScryptKdf.java
@@ -16,7 +16,7 @@ class ScryptKdf implements PasswordBasedKdf {
private static final Logger LOG =
Logger.getLogger(ScryptKdf.class.getName());
- private static final int MIN_COST = 512; // Min parameter N
+ private static final int MIN_COST = 256; // Min parameter N
private static final int MAX_COST = 1024 * 1024; // Max parameter N
private static final int BLOCK_SIZE = 8; // Parameter r
private static final int PARALLELIZATION = 1; // Parameter p
diff --git a/bramble-core/src/test/java/org/briarproject/bramble/crypto/ScryptKdfTest.java b/bramble-core/src/test/java/org/briarproject/bramble/crypto/ScryptKdfTest.java
index d539252455..f7cbfe05ec 100644
--- a/bramble-core/src/test/java/org/briarproject/bramble/crypto/ScryptKdfTest.java
+++ b/bramble-core/src/test/java/org/briarproject/bramble/crypto/ScryptKdfTest.java
@@ -56,6 +56,7 @@ public class ScryptKdfTest extends BrambleTestCase {
@Test
public void testCalibration() throws Exception {
Clock clock = new ArrayClock(
+ 0, 50, // Duration for cost 256
0, 100, // Duration for cost 512
0, 200, // Duration for cost 1024
0, 400, // Duration for cost 2048
@@ -65,6 +66,15 @@ public class ScryptKdfTest extends BrambleTestCase {
assertEquals(4096, kdf.chooseCostParameter());
}
+ @Test
+ public void testCalibrationChoosesMinCost() throws Exception {
+ Clock clock = new ArrayClock(
+ 0, 2000 // Duration for cost 256 is already too high
+ );
+ PasswordBasedKdf kdf = new ScryptKdf(clock);
+ assertEquals(256, kdf.chooseCostParameter());
+ }
+
private static class ArrayClock implements Clock {
private final long[] times;
--
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