Finished BLISS signature generation

2014-11-29 14:51:17 +01:00
parent edd72b6bb9
commit e71813e56d
12 changed files with 1178 additions and 165 deletions
@@ -0,0 +1,167 @@
+/*
+ * Copyright (C) 2014 Andreas Steffen
+ * HSR Hochschule fuer Technik Rapperswil
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program 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 General Public License
+ * for more details.
+ */
+
+#include "bliss_utils.h"
+
+#include <asn1/asn1.h>
+#include <crypto/hashers/hasher.h>
+#include <utils/debug.h>
+
+/**
+ * See header.
+ */
+int32_t bliss_utils_scalar_product(int32_t *x, int32_t *y, int n)
+{
+	int32_t product = 0;
+	int i;
+
+	for (i = 0; i < n; i++)
+	{
+		product += x[i] * y[i];
+	}
+
+	return product;
+}
+
+/**
+ * See header.
+ */
+void bliss_utils_round_and_drop(bliss_param_set_t *set, int32_t *x, int16_t *xd)
+{
+	int32_t factor;
+	int i;
+
+	factor = 1 << set->d;
+
+	for (i = 0; i < set->n; i++)
+	{
+		xd[i] = ((x[i] + (factor >> 1)) / factor) % set->p;
+	}
+}
+
+/**
+ * See header.
+ */
+bool bliss_utils_generate_c(hasher_t *hasher, chunk_t data_hash, uint16_t *ud,
+							int n, uint16_t kappa, uint16_t *c_indices)
+{
+	int i, j;
+	uint64_t extra_bits;
+	uint16_t index, rounds = 0;
+	uint8_t hash[HASH_SIZE_SHA512], un16_buf[2];
+	chunk_t un16 = { un16_buf, 2 };
+	bool index_taken[n];
+
+	while (TRUE)
+	{
+		if (!hasher->get_hash(hasher, data_hash, NULL))
+		{
+			return FALSE;
+		}
+
+		for (i = 0; i < n; i++)
+		{
+			htoun16(un16_buf, ud[i]);
+			if (!hasher->get_hash(hasher, un16, NULL))
+			{
+				return FALSE;
+			}
+			index_taken[i] = FALSE;
+		}
+
+		htoun16(un16_buf, rounds++);
+		if (!hasher->get_hash(hasher, un16, hash))
+		{
+			return FALSE;
+		}
+
+		extra_bits = untoh64(hash + sizeof(hash) - sizeof(uint64_t));
+
+		for (i = 0, j = 0; j < sizeof(hash); j++)
+		{
+			index = 2 * (uint16_t)hash[i] + (extra_bits & 1);
+			if (!index_taken[index])
+			{
+				c_indices[i++] = index;
+				index_taken[index] = TRUE;
+			}
+			if (i == kappa)
+			{
+				return TRUE;
+			}
+		}
+	}
+}
+
+/**
+ * See header.
+ */
+bool bliss_utils_check_norms(bliss_param_set_t *set, int32_t *z1, int16_t *z2d)
+{
+	int32_t z2ds[set->n];
+	int32_t z1_min, z1_max, norm;
+	int16_t z2d_min, z2d_max;
+	int i;
+
+	/* some statistics on the values of z1 and z2d */
+	z1_min  = z1_max  = z1[0];
+	z2d_min = z2d_max = z2d[0];
+
+	for (i = 1; i < set->n; i++)
+	{
+		if (z1[i] < z1_min)
+		{
+			z1_min = z1[i];
+		}
+		else if (z1[i] > z1_max)
+		{
+			z1_max = z1[i];
+		}
+		if (z2d[i] < z2d_min)
+		{
+			z2d_min = z2d[i];
+		}
+		else if (z2d[i] > z2d_max)
+		{
+			z2d_max = z2d[i];
+		}
+	}
+	DBG2(DBG_LIB, "z1 = %d..%d, z2d = %d..%d", z1_min, z1_max, z2d_min, z2d_max);
+
+	/* Restriction on infinite norm */
+	for (i = 0; i < set->n; i++)
+	{
+		z2ds[i] = (1 << set->d) * z2d[i];
+
+		if (z1[i] >=  set->B_inf || z2ds[i] >=  set->B_inf ||
+			z1[i] <= -set->B_inf || z2ds[i] <= -set->B_inf)
+		{
+			DBG2(DBG_LIB, "signature rejected due to excessive infinite norm");
+			return FALSE;
+		}
+	}
+
+	/* Restriction on l2-norm */
+	norm = bliss_utils_scalar_product(z1, z1, set->n) +
+		   bliss_utils_scalar_product(z2ds, z2ds, set->n);
+
+	if (norm >= set->B_l2)
+	{
+		DBG2(DBG_LIB, "signature rejected due to excessive l2-norm");
+		return FALSE;
+	}
+
+	return TRUE;
+}