From 98d37116f1dc542010b2d65dcda71871eeca8c87 Mon Sep 17 00:00:00 2001
From: Dennis Brentjes <d.brentjes@gmail.com>
Date: Thu, 3 Nov 2016 14:10:59 +0100
Subject: Fixed the permutation step and reduced some code duplication.

---
 libcmix/cmix.c |  2 +-
 node/node.cpp  | 95 ++++++++++++++++++++++++++++++++++------------------------
 2 files changed, 57 insertions(+), 40 deletions(-)

diff --git a/libcmix/cmix.c b/libcmix/cmix.c
index 6a39767..4893c6c 100644
--- a/libcmix/cmix.c
+++ b/libcmix/cmix.c
@@ -184,7 +184,7 @@ enum cmix_error multiply_s(struct CMixContext const* ctx, char* r_out_buffer, ch
 	GroupElement random_s;
 	GroupElement message_s;
 	
-	ctx->api.encrypt(&random_s, &message_s, ctx->s[index], ctx->network_key);
+	ctx->api.encrypt(&random_s, &message_s, ctx->s[ctx->permutation[index]], ctx->network_key);
 	
 	GroupElement random_pirs = ctx->api.multiply(random_r, random_s, true);
 	GroupElement message_pirs = ctx->api.multiply(message_r, message_s, true);
diff --git a/node/node.cpp b/node/node.cpp
index fc41656..98b5873 100644
--- a/node/node.cpp
+++ b/node/node.cpp
@@ -114,50 +114,66 @@ void Node::handle_node_secretkey(cmix_proto::SecretKey const& secret)
 	}
 }
 
-void Node::handle_node_prepre(cmix_proto::PrePre const& pre) {
-	if(network_settings.is_first) {
+template <typename T>
+cmix_proto::PreMix fill_precomputation_mix_message(CMixContext const& ctx, T const& rs, T const& ms) {
+	cmix_proto::PreMix premix;
+	for(size_t i = 0; i < ctx.nr_participants; ++i) {
+		auto new_pos = ctx.permutation[i];
+		size_t el_len = get_group_element_array_size(&ctx);
 		
-		cmix_proto::PreMix premix;
-		for(int i = 0; i < cmix_ctx.nr_participants; ++i) {
-			auto new_pos = cmix_ctx.permutation[i];
-			size_t el_len = get_group_element_array_size(&cmix_ctx);
-			
-			premix.mutable_r_epirs(new_pos)->resize(el_len);
-			premix.mutable_m_epirs(new_pos)->resize(el_len);
-			
-			multiply_s(
-				&cmix_ctx,
-				&(*premix.mutable_r_epirs(new_pos))[0],
-				&(*premix.mutable_m_epirs(new_pos))[0],
-				pre.r_er(i).data(),
-				pre.m_er(i).data(),
-				i
-			);
-		}
+		premix.mutable_r_epirs(new_pos)->resize(el_len);
+		premix.mutable_m_epirs(new_pos)->resize(el_len);
 		
-		next_node.async_send(premix);
+		multiply_s(
+			&ctx,
+			&(*premix.mutable_r_epirs(new_pos))[0],
+			&(*premix.mutable_m_epirs(new_pos))[0],
+			rs.Get(i).data(),
+			ms.Get(i).data(),
+			i
+		);
+	}
+	return premix;
+}
+
+template <typename T>
+cmix_proto::PrePre fill_precomputation_pre_message(CMixContext& ctx, T const& rs, T const& ms) {
+	if(start_mix(&ctx, rs.size()) != no_error) {
+		exit(-1);
+	}
+	
+	if(initialize_mix_randomness(&ctx) != no_error) {
+		exit(-1);
+	}
+	
+	cmix_proto::PrePre prepre;
+	
+	for(int i = 0; i < rs.size(); ++i) {
+		size_t len = get_group_element_array_size(&ctx);
 		
-	} else {
-		if(start_mix(&cmix_ctx, pre.r_er_size()) != no_error) {
-			exit(-1);
-		}
+		prepre.mutable_m_er(i)->resize(len);
+		prepre.mutable_r_er(i)->resize(len);
 		
-		if(initialize_mix_randomness(&cmix_ctx) != no_error) {
+		if(encrypt_r_and_multiply(
+			&ctx, 
+			&(*prepre.mutable_r_er(i))[0],
+			&(*prepre.mutable_m_er(i))[0],
+			rs.Get(i).data(),
+			ms.Get(i).data(),
+			i
+		) != no_error) {
 			exit(-1);
 		}
-		
-		cmix_proto::PrePre prepre;
-		
-		for(int i = 0; i < pre.m_er_size(); ++i) {
-			size_t len = get_group_element_array_size(&cmix_ctx);
-			
-			prepre.mutable_m_er(i)->resize(len);
-			prepre.mutable_r_er(i)->resize(len);
-			
-			if(encrypt_r_and_multiply(&cmix_ctx, &(*prepre.mutable_r_er(i))[0], &(*prepre.mutable_m_er(i))[0], pre.r_er(i).data(), pre.m_er(i).data(), i) != no_error) {
-				exit(-1);
-			}
-		}
+	}
+	return prepre;
+}
+
+void Node::handle_node_prepre(cmix_proto::PrePre const& pre) {
+	if(network_settings.is_first) {
+		cmix_proto::PreMix premix = fill_precomputation_mix_message(cmix_ctx, pre.r_er(), pre.m_er());
+		next_node.async_send(premix);
+	} else {
+		cmix_proto::PrePre prepre = fill_precomputation_pre_message(cmix_ctx, pre.r_er(), pre.m_er());
 		next_node.async_send(prepre);
 	}
 }
@@ -166,7 +182,8 @@ void Node::handle_node_premix(cmix_proto::PreMix const& premix) {
 	if(network_settings.is_first) {
 		
 	} else {
-		
+		cmix_proto::PreMix n_premix = fill_precomputation_mix_message(cmix_ctx, premix.r_epirs(), premix.m_epirs());
+		next_node.async_send(n_premix);
 	}
 }
 
-- 
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