4 files changed, 10 insertions, 13 deletions
diff --git a/Firestore/Example/Tests/Integration/FSTDatastoreTests.m b/Firestore/Example/Tests/Integration/FSTDatastoreTests.m
index bf2c44b..047f059 100644
--- a/Firestore/Example/Tests/Integration/FSTDatastoreTests.m
+++ b/Firestore/Example/Tests/Integration/FSTDatastoreTests.m
@@ -40,7 +40,6 @@
 #import "Firestore/Source/Remote/FSTRemoteStore.h"
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
-#import "Firestore/Source/Util/FSTUtil.h"
 
 #import "Firestore/Example/Tests/Util/FSTIntegrationTestCase.h"
 
diff --git a/Firestore/Source/Remote/FSTExponentialBackoff.m b/Firestore/Source/Remote/FSTExponentialBackoff.mm
index 2e06238..ad27c25 100644
--- a/Firestore/Source/Remote/FSTExponentialBackoff.m
+++ b/Firestore/Source/Remote/FSTExponentialBackoff.mm
@@ -16,9 +16,12 @@
 
 #import "Firestore/Source/Remote/FSTExponentialBackoff.h"
 
+#include <random>
+
+#include "Firestore/src/support/secure_random.h"
+
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
 #import "Firestore/Source/Util/FSTLogger.h"
-#import "Firestore/Source/Util/FSTUtil.h"
 
 @interface FSTExponentialBackoff ()
 - (instancetype)initWithDispatchQueue:(FSTDispatchQueue *)dispatchQueue
@@ -33,7 +36,9 @@
 @property(nonatomic) NSTimeInterval currentBase;
 @end
 
-@implementation FSTExponentialBackoff
+@implementation FSTExponentialBackoff {
+  firestore::SecureRandom _secureRandom;
+}
 
 - (instancetype)initWithDispatchQueue:(FSTDispatchQueue *)dispatchQueue
                          initialDelay:(NSTimeInterval)initialDelay
@@ -90,7 +95,9 @@
 
 /** Returns a random value in the range [-currentBase/2, currentBase/2] */
 - (NSTimeInterval)jitterDelay {
-  return ([FSTUtil randomDouble] - 0.5) * _currentBase;
+  std::uniform_real_distribution<double> dist;
+  double random_double = dist(_secureRandom);
+  return (random_double - 0.5) * _currentBase;
 }
 
 @end
diff --git a/Firestore/Source/Util/FSTUtil.h b/Firestore/Source/Util/FSTUtil.h
index 3985d10..230c72a 100644
--- a/Firestore/Source/Util/FSTUtil.h
+++ b/Firestore/Source/Util/FSTUtil.h
@@ -20,9 +20,6 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface FSTUtil : NSObject
 
-/** Generates a random double between 0 and 1. */
-+ (double)randomDouble;
-
 /** Generates a random ID suitable for use as a document ID. */
 + (NSString *)autoID;
 
diff --git a/Firestore/Source/Util/FSTUtil.m b/Firestore/Source/Util/FSTUtil.m
index a25cd7e..47a8821 100644
--- a/Firestore/Source/Util/FSTUtil.m
+++ b/Firestore/Source/Util/FSTUtil.m
@@ -18,18 +18,12 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-static const double kArc4RandomMax = 0x100000000;
-
 static const int kAutoIDLength = 20;
 static NSString *const kAutoIDAlphabet =
     @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
 
 @implementation FSTUtil
 
-+ (double)randomDouble {
-  return ((double)arc4random() / kArc4RandomMax);
-}
-
 + (NSString *)autoID {
   unichar autoID[kAutoIDLength];
   for (int i = 0; i < kAutoIDLength; i++) {