From ff40048d55bb07fab8f49c7815be38a4a6d799b9 Mon Sep 17 00:00:00 2001
From: hasufell <hasufell@hasufell.de>
Date: Mon, 14 Apr 2014 22:29:36 +0200
Subject: [PATCH] RAND: basic randomization

No sanity checks like minimum number of non-NULL coefficients
for the polynomial.
---
 src/rand.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/rand.h | 35 ++++++++++++++++++++
 2 files changed, 132 insertions(+)
 create mode 100644 src/rand.c
 create mode 100644 src/rand.h

diff --git a/src/rand.c b/src/rand.c
new file mode 100644
index 0000000..db61d48
--- /dev/null
+++ b/src/rand.c
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2014 hasufell
+ *
+ * This file is part of a hasufell project.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA  02110-1301  USA
+ */
+
+#include "context.h"
+#include "err.h"
+#include "rand.h"
+#include "poly.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <tompoly.h>
+#include <tommath.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+
+/**
+ * Gets randomly a small integer
+ * from the set {-1, 0, 1} using /dev/urandom.
+ *
+ * @param sign stores the signness [out]
+ * @return random small integer
+ */
+mp_digit get_urnd_int_small(int *sign)
+{
+	int random_data;
+	mp_digit random_int;
+	ssize_t result;
+
+	random_data = open("/dev/urandom", O_RDONLY);
+	if ((result = read(random_data, &random_int, sizeof(random_int))) < 0)
+		NTRU_ABORT("Unable to read /dev/urandom");
+	close(random_int);
+
+	if ((random_int % 2) == 0) {
+		random_int = 0;
+		*sign = 0;
+	} else if (random_int % 3) {
+		random_int = 1;
+		*sign = 1;
+	} else {
+		random_int = 1;
+		*sign = 0;
+	}
+
+	return random_int;
+}
+
+/**
+ * Gets a random polynomial with coefficients
+ * from the set {-1 ,0 ,1} using /dev/urandom.
+ *
+ * @param ctx the NTRU context
+ * @return newly allocated polynomial
+ */
+pb_poly *get_urnd_poly_small(pqc_context *ctx)
+{
+	mp_int *chara = malloc(sizeof(mp_int));
+	init_integer(chara);
+	pb_poly *poly = malloc(sizeof(pb_poly));
+	init_polynom_size(poly, chara, ctx->N);
+
+	for (int i = 0; i < ctx->N; i++) {
+		int sign;
+		int c = get_urnd_int_small(&sign);
+
+		mp_set(&(poly->terms[i]), (mp_digit)c);
+
+		if (sign == 1)
+			poly->terms[i].sign = 1;
+	}
+	poly->used = ctx->N;
+	pb_clamp(poly);
+
+	return poly;
+}
+
diff --git a/src/rand.h b/src/rand.h
new file mode 100644
index 0000000..41206bd
--- /dev/null
+++ b/src/rand.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2014 hasufell
+ *
+ * This file is part of a hasufell project.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA  02110-1301  USA
+ */
+
+
+#ifndef NTRU_RAND_H
+#define NTRU_RAND_H
+
+#include "context.h"
+
+#include <tompoly.h>
+
+
+mp_digit get_urnd_int_small(int *sign);
+
+pb_poly *get_urnd_poly_small(pqc_context *ctx);
+
+#endif /* NTRU_RAND_H */