Fix for #168
diff --git a/uECC.c b/uECC.c
index c08b7ac..17c0f6f 100644
--- a/uECC.c
+++ b/uECC.c
@@ -1210,7 +1210,7 @@
bcopy((uint8_t *) native, bits, bits_size);
#else
uECC_vli_bytesToNative(native, bits, bits_size);
-#endif
+#endif
if (bits_size * 8 <= (unsigned)curve->num_n_bits) {
return;
}
@@ -1239,6 +1239,7 @@
uECC_word_t tmp[uECC_MAX_WORDS];
uECC_word_t s[uECC_MAX_WORDS];
uECC_word_t *k2[2] = {tmp, s};
+ uECC_word_t *initial_Z = 0;
#if uECC_VLI_NATIVE_LITTLE_ENDIAN
uECC_word_t *p = (uECC_word_t *)signature;
#else
@@ -1255,7 +1256,15 @@
}
carry = regularize_k(k, tmp, s, curve);
- EccPoint_mult(p, curve->G, k2[!carry], 0, num_n_bits + 1, curve);
+ /* If an RNG function was specified, try to get a random initial Z value to improve
+ protection against side-channel attacks. */
+ if (g_rng_function) {
+ if (!uECC_generate_random_int(k2[carry], curve->p, num_words)) {
+ return 0;
+ }
+ initial_Z = k2[carry];
+ }
+ EccPoint_mult(p, curve->G, k2[!carry], initial_Z, num_n_bits + 1, curve);
if (uECC_vli_isZero(p, num_words)) {
return 0;
}
@@ -1299,7 +1308,7 @@
bcopy((uint8_t *) signature + curve->num_bytes, (uint8_t *) s, curve->num_bytes);
#else
uECC_vli_nativeToBytes(signature + curve->num_bytes, curve->num_bytes, s);
-#endif
+#endif
return 1;
}
@@ -1472,7 +1481,7 @@
uECC_word_t *_public = (uECC_word_t *)public_key;
#else
uECC_word_t _public[uECC_MAX_WORDS * 2];
-#endif
+#endif
uECC_word_t r[uECC_MAX_WORDS], s[uECC_MAX_WORDS];
wordcount_t num_words = curve->num_words;
wordcount_t num_n_words = BITS_TO_WORDS(curve->num_n_bits);