From: Christoph Egger <egger@cs.fau.de>
Date: Wed, 15 Jan 2020 16:23:07 +0000 (+0100)
Subject: optimize
X-Git-Url: https://git.siccegge.de//index.cgi?p=software%2FDIPE.git;a=commitdiff_plain;h=f20d9414f3017939d6aec74c70c0d5c0380edfae

optimize
---

diff --git a/src/SS.cxx b/src/SS.cxx
index 721c004..426072b 100644
--- a/src/SS.cxx
+++ b/src/SS.cxx
@@ -48,7 +48,7 @@ namespace {
 	/* https://proofwiki.org/wiki/Inverse_of_Vandermonde_Matrix	
 	 * Contract: result is allocated but not initialized size x size array
 	 */
-	void dipe_ss_inverse_vandermonde(dipe_param_t param, size_t size, element_t* elements, element_t** result) {
+	void dipe_ss_inverse_vandermonde(dipe_param_t param, bool flat, size_t size, element_t* elements, element_t** result) {
 		/* b_ij = (-1)^{n-i} e_{n-i}() / \Prod ()
 		 */
 		element_t numerator, denominator;
@@ -58,6 +58,8 @@ namespace {
 		element_init_Zr(tmp, param->pairing);
 		
 		for (size_t i = 0; i < size; ++i) {
+			if (flat && i > 0) continue;
+			
 			for (size_t j = 0; j < size; ++j) {
 				element_init_Zr(result[i][j], param->pairing);
 
@@ -99,7 +101,7 @@ void dipe_ss_share(dipe_param_t param, size_t id_size, element_t* ids, size_t fi
 	for (size_t i = 0; i < id_size; ++i) {
 		b[i] = (element_t*)calloc(id_size, sizeof(element_t));
 	}
-	dipe_ss_inverse_vandermonde(param, id_size, ids, b);
+	dipe_ss_inverse_vandermonde(param, false, id_size, ids, b);
 
 	/* Compute Secret */
 	for (size_t k = 0; k < share_size; ++k) {
@@ -168,11 +170,9 @@ void dipe_ss_recover(dipe_param_t param, size_t id_size, element_t* ids, size_t
 
 	/* Precompute V_I^{-1} needed in several steps */
 	/* Actually for recover we only need the values b[0][j] */
-	element_t** b = (element_t**)calloc(id_size, sizeof(element_t*));
-	for (size_t i = 0; i < id_size; ++i) {
-		b[i] = (element_t*)calloc(id_size, sizeof(element_t));
-	}
-	dipe_ss_inverse_vandermonde(param, id_size, ids, b);
+	element_t** b = (element_t**)calloc(1, sizeof(element_t*));
+	b[0] = (element_t*)calloc(id_size, sizeof(element_t));
+	dipe_ss_inverse_vandermonde(param, true, id_size, ids, b);
 
 	/* Compute Secret */
 	for (size_t k = 0; k < share_size; ++k) {
@@ -183,12 +183,10 @@ void dipe_ss_recover(dipe_param_t param, size_t id_size, element_t* ids, size_t
 		}
 	}
 
-	for (size_t i = 0; i < id_size; ++i) {
-		for (size_t j = 0; j < id_size; ++j) {
-			element_clear(b[i][j]);
-		}
-		free(b[i]);
+	for (size_t j = 0; j < id_size; ++j) {
+		element_clear(b[0][j]);
 	}
+	free(b[0]);
 	free(b);
 	element_clear(tmp);
 }