X-Git-Url: https://www.bearssl.org/gitweb//home/git/?p=BearSSL;a=blobdiff_plain;f=src%2Fint%2Fi15_modpow.c;fp=src%2Fint%2Fi15_modpow.c;h=9bf304e50ad189c905f458171b5b7e04a701e007;hp=0000000000000000000000000000000000000000;hb=2f454aad577ae53798935cc32438a2d3f02ba31f;hpb=bd3036844bd20b2b8d7bce7fee5ad010ce401915

diff --git a/src/int/i15_modpow.c b/src/int/i15_modpow.c
new file mode 100644
index 0000000..9bf304e
--- /dev/null
+++ b/src/int/i15_modpow.c
@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see inner.h */
+void
+br_i15_modpow(uint16_t *x,
+	const unsigned char *e, size_t elen,
+	const uint16_t *m, uint16_t m0i, uint16_t *t1, uint16_t *t2)
+{
+	size_t mlen;
+	unsigned k;
+
+	mlen = ((m[0] + 31) >> 4) * sizeof m[0];
+	memcpy(t1, x, mlen);
+	br_i15_to_monty(t1, m);
+	br_i15_zero(x, m[0]);
+	x[1] = 1;
+	for (k = 0; k < ((unsigned)elen << 3); k ++) {
+		uint32_t ctl;
+
+		ctl = (e[elen - 1 - (k >> 3)] >> (k & 7)) & 1;
+		br_i15_montymul(t2, x, t1, m, m0i);
+		CCOPY(ctl, x, t2, mlen);
+		br_i15_montymul(t2, t1, t1, m, m0i);
+		memcpy(t1, t2, mlen);
+	}
+}