From 40c6f395db0f671effe02bcad084ca6d239a6bd9 Mon Sep 17 00:00:00 2001
From: Davis Mosenkovs <davikovs@gmail.com>
Date: Wed, 4 Nov 2026 00:45:48 +0200
Subject: [PATCH] Mix entropy in Dice PRNG on every Roll

This improves entropy of Dice and makes PRNG state recovery harder.
As a pleasant side effect this also makes the Dice app more like a
physical dice - dependent on how it is shaken, but in a hard to predict
manner.
Using PRNG output as one of the seeds preserves 32-bits of previous PRNG
entropy when reseeding. For std::minstd_rand that means entire entropy.
---
 src/displayapp/screens/Dice.cpp | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/displayapp/screens/Dice.cpp b/src/displayapp/screens/Dice.cpp
index 302c5f3fb2..05d34e5b49 100644
--- a/src/displayapp/screens/Dice.cpp
+++ b/src/displayapp/screens/Dice.cpp
@@ -43,12 +43,6 @@ Dice::Dice(Controllers::MotionController& motionController,
            Controllers::MotorController& motorController,
            Controllers::Settings& settingsController)
   : motorController {motorController}, motionController {motionController}, settingsController {settingsController} {
-  std::seed_seq sseq {static_cast<uint32_t>(xTaskGetTickCount()),
-                      static_cast<uint32_t>(motionController.X()),
-                      static_cast<uint32_t>(motionController.Y()),
-                      static_cast<uint32_t>(motionController.Z())};
-  gen.seed(sseq);
-
   lv_obj_t* nCounterLabel = MakeLabel(&jetbrains_mono_bold_20,
                                       LV_COLOR_WHITE,
                                       LV_LABEL_LONG_EXPAND,
@@ -155,6 +149,13 @@ void Dice::Refresh() {
 }
 
 void Dice::Roll() {
+  std::seed_seq sseq {static_cast<uint32_t>(xTaskGetTickCount()),
+                      static_cast<uint32_t>(motionController.X()),
+                      static_cast<uint32_t>(motionController.Y()),
+                      static_cast<uint32_t>(motionController.Z()),
+                      static_cast<uint32_t>(gen())};
+  gen.seed(sseq);
+
   uint8_t resultIndividual;
   uint16_t resultTotal = 0;
   std::uniform_int_distribution<> distrib(1, dCounter.GetValue());