X-Git-Url: https://www.bearssl.org/gitweb//home/git/?p=BearSSL;a=blobdiff_plain;f=src%2Fec%2Fec_keygen.c;fp=src%2Fec%2Fec_keygen.c;h=02a309625d564bbef129c2c7798736a09ed619ef;hp=0000000000000000000000000000000000000000;hb=d8fa415fcabecb7d7c8461d8edbe2f265911e72c;hpb=cfbc702d3d64c209784b664eeab8867b603f4d4c

diff --git a/src/ec/ec_keygen.c b/src/ec/ec_keygen.c
new file mode 100644
index 0000000..02a3096
--- /dev/null
+++ b/src/ec/ec_keygen.c
@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2018 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 bearssl_ec.h */
+size_t
+br_ec_keygen(const br_prng_class **rng_ctx,
+	const br_ec_impl *impl, br_ec_private_key *sk,
+	void *kbuf, int curve)
+{
+	const unsigned char *order;
+	unsigned char *buf;
+	size_t len;
+	unsigned mask;
+
+	if (curve < 0 || curve >= 32
+		|| ((impl->supported_curves >> curve) & 1) == 0)
+	{
+		return 0;
+	}
+	order = impl->order(curve, &len);
+	while (len > 0 && *order == 0) {
+		order ++;
+		len --;
+	}
+	if (kbuf == NULL || len == 0) {
+		return len;
+	}
+	mask = order[0];
+	mask |= (mask >> 1);
+	mask |= (mask >> 2);
+	mask |= (mask >> 4);
+
+	/*
+	 * We generate sequences of random bits of the right size, until
+	 * the value is strictly lower than the curve order (we also
+	 * check for all-zero values, which are invalid).
+	 */
+	buf = kbuf;
+	for (;;) {
+		size_t u;
+		unsigned cc, zz;
+
+		(*rng_ctx)->generate(rng_ctx, buf, len);
+		buf[0] &= mask;
+		cc = 0;
+		u = len;
+		zz = 0;
+		while (u -- > 0) {
+			cc = ((unsigned)(buf[u] - order[u] - cc) >> 8) & 1;
+			zz |= buf[u];
+		}
+		if (cc != 0 && zz != 0) {
+			break;
+		}
+	}
+
+	if (sk != NULL) {
+		sk->curve = curve;
+		sk->x = buf;
+		sk->xlen = len;
+	}
+	return len;
+}