prevent optimization in algorithms

Signed-off-by: Harshil Jani <[email protected]>

Author: Harshil-Jani

examples/ecdh.c

@@ -18,12 +18,12 @@
 
 
 int main(void) {
-    unsigned char seckey1[32];
-    unsigned char seckey2[32];
+    volatile unsigned char seckey1[32];
+    volatile unsigned char seckey2[32];
     unsigned char compressed_pubkey1[33];
     unsigned char compressed_pubkey2[33];
-    unsigned char shared_secret1[32];
-    unsigned char shared_secret2[32];
+    volatile unsigned char shared_secret1[32];
+    volatile unsigned char shared_secret2[32];
     unsigned char randomize[32];
     int return_val;
     size_t len;
@@ -112,7 +112,7 @@ int main(void) {
      * example through "out of bounds" array access (see Heartbleed), Or the OS
      * swapping them to disk. Hence, we overwrite the secret key buffer with zeros.
      *
-     * TODO: Prevent these writes from being optimized out, as any good compiler
+     * Here we are preventing these writes from being optimized out, as any good compiler
      * will remove any writes that aren't used. */
     memset(seckey1, 0, sizeof(seckey1));
     memset(seckey2, 0, sizeof(seckey2));

examples/ecdsa.c

@@ -29,7 +29,7 @@ int main(void) {
         0x61, 0x2B, 0x1F, 0xCE, 0x77, 0xC8, 0x69, 0x34,
         0x5B, 0xFC, 0x94, 0xC7, 0x58, 0x94, 0xED, 0xD3,
     };
-    unsigned char seckey[32];
+    volatile unsigned char seckey[32];
     unsigned char randomize[32];
     unsigned char compressed_pubkey[33];
     unsigned char serialized_signature[64];
@@ -125,7 +125,7 @@ int main(void) {
      * example through "out of bounds" array access (see Heartbleed), Or the OS
      * swapping them to disk. Hence, we overwrite the secret key buffer with zeros.
      *
-     * TODO: Prevent these writes from being optimized out, as any good compiler
+     * Here we are preventing these writes from being optimized out, as any good compiler
      * will remove any writes that aren't used. */
     memset(seckey, 0, sizeof(seckey));
 

examples/schnorr.c

@@ -21,7 +21,7 @@ int main(void) {
     unsigned char msg[12] = "Hello World!";
     unsigned char msg_hash[32];
     unsigned char tag[17] = "my_fancy_protocol";
-    unsigned char seckey[32];
+    volatile unsigned char seckey[32];
     unsigned char randomize[32];
     unsigned char auxiliary_rand[32];
     unsigned char serialized_pubkey[32];
@@ -140,7 +140,7 @@ int main(void) {
      * example through "out of bounds" array access (see Heartbleed), Or the OS
      * swapping them to disk. Hence, we overwrite the secret key buffer with zeros.
      *
-     * TODO: Prevent these writes from being optimized out, as any good compiler
+     * Here we are preventing these writes from being optimized out, as any good compiler
      * will remove any writes that aren't used. */
     memset(seckey, 0, sizeof(seckey));