From 3d81da6d1ad500cd99ecb81f0ade2d73750d9c0f Mon Sep 17 00:00:00 2001
From: merlokk <olegmsn@gmail.com>
Date: Wed, 1 Nov 2017 16:18:13 +0200
Subject: [PATCH] added validate_prng_nonce from iceman1001 fork

---
 common/crapto1/crapto1.c | 11 +++++++++++
 common/crapto1/crapto1.h |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/common/crapto1/crapto1.c b/common/crapto1/crapto1.c
index 9398a1f3..b77842e9 100644
--- a/common/crapto1/crapto1.c
+++ b/common/crapto1/crapto1.c
@@ -426,6 +426,17 @@ int nonce_distance(uint32_t from, uint32_t to)
 	return (65535 + dist[to >> 16] - dist[from >> 16]) % 65535;
 }
 
+/** validate_prng_nonce
+ * Determine if nonce is deterministic. ie: Suspectable to Darkside attack.
+ * returns
+ *   true = weak prng
+ *   false = hardend prng
+ */
+bool validate_prng_nonce(uint32_t nonce) {
+	// init prng table:
+	nonce_distance(nonce, nonce);
+	return ((65535 - dist[nonce >> 16] + dist[nonce & 0xffff]) % 65535) == 16;
+}
 
 static uint32_t fastfwd[2][8] = {
 	{ 0, 0x4BC53, 0xECB1, 0x450E2, 0x25E29, 0x6E27A, 0x2B298, 0x60ECB},
diff --git a/common/crapto1/crapto1.h b/common/crapto1/crapto1.h
index 8e79d224..154e4cc8 100644
--- a/common/crapto1/crapto1.h
+++ b/common/crapto1/crapto1.h
@@ -20,6 +20,7 @@
 #ifndef CRAPTO1_INCLUDED
 #define CRAPTO1_INCLUDED
 #include <stdint.h>
+#include <stdbool.h>
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -48,6 +49,7 @@ uint8_t lfsr_rollback_bit(struct Crypto1State* s, uint32_t in, int fb);
 uint8_t lfsr_rollback_byte(struct Crypto1State* s, uint32_t in, int fb);
 uint32_t lfsr_rollback_word(struct Crypto1State* s, uint32_t in, int fb);
 int nonce_distance(uint32_t from, uint32_t to);
+extern bool validate_prng_nonce(uint32_t nonce);
 #define FOREACH_VALID_NONCE(N, FILTER, FSIZE)\
 	uint32_t __n = 0,__M = 0, N = 0;\
 	int __i;\