Moves cmix calculation stuff outisde of the node class.

Moves the computations and cryptography to the the libcmix library
where we can group and memory manage the underlying crypto-library.

1 files changed, 180 insertions, 0 deletions

diff --git a/libcmix/cmix.c b/libcmix/cmix.c
index e0256cf..6a39767 100644
--- a/libcmix/cmix.c
+++ b/libcmix/cmix.c
@@ -2,6 +2,7 @@
 #include "cmix.h"
 
 #include <string.h>
+#include <stdlib.h>
 
 enum cmix_error permutation(struct CMixBuffer b) {
 	return no_error;
@@ -36,3 +37,182 @@ enum cmix_error calculate_shared_key_part(struct Bignum* result, struct Bignum p
 	}
 	return no_error;
 }
+
+struct CMixContext initialize_cmix_context(struct Api api) {
+	return (struct CMixContext){
+		.api = api,
+		.nr_participants = 0,
+		.r = NULL,
+		.s = NULL,
+		.permutation = NULL,
+		.pirs = NULL
+	};
+}
+
+void release_mix(struct CMixContext* ctx) {
+	for(size_t i = 0; i < ctx->nr_participants; ++i) {
+		ctx->api.free_group_element(ctx->r[i]);
+		ctx->api.free_group_element(ctx->s[i]);
+		ctx->api.free_group_element(ctx->pirs[i]);
+	}
+	free(ctx->r);
+	free(ctx->s);
+	free(ctx->permutation);
+	free(ctx->pirs);
+}
+
+void deinitialize(struct CMixContext* ctx)
+{
+	ctx->api.free_keypair(&ctx->keypair);
+	release_mix(ctx);
+}
+
+void element_to_buffer(struct CMixContext const* ctx, char* out_buffer, GroupElement element) {
+	size_t el_size = get_group_element_array_size(ctx);
+	
+	unsigned char* buffer;
+	size_t len;
+	
+	ctx->api.element_to_array(&buffer, &len, element);
+	size_t diff = el_size - len;
+	memcpy(out_buffer + diff, buffer, len);
+	ctx->api.free_buffer(buffer);
+}
+
+enum cmix_error initialize_keypair(struct CMixContext* ctx)
+{
+	ctx->keypair = ctx->api.create_keypair();
+	return no_error;
+}
+
+enum cmix_error get_public_key(struct CMixContext const* ctx, char* buffer)
+{
+	element_to_buffer(ctx, buffer, ctx->keypair.pub);
+	return no_error;
+}
+
+enum cmix_error add_public_share(struct CMixContext const* ctx, char* buffer, char const* share) {
+	size_t len = get_group_element_array_size(ctx);
+	
+	GroupElement el;
+	ctx->api.add_public_share(&el, share, len, ctx->keypair.pub);
+	
+	element_to_buffer(ctx, buffer, el);
+	ctx->api.free_group_element(el);
+}
+
+enum cmix_error alloc_mix(struct CMixContext* ctx) {
+	ctx->r = (GroupElement*) calloc(ctx->nr_participants, sizeof(GroupElement));
+	ctx->s = (GroupElement*) calloc(ctx->nr_participants, sizeof(GroupElement));
+	ctx->permutation = (unsigned int*) calloc(ctx->nr_participants, sizeof(unsigned int));
+	ctx->pirs = (GroupElement*) calloc(ctx->nr_participants, sizeof(GroupElement));
+	if(!ctx->r || !ctx->s || !ctx->permutation || !ctx->pirs) {
+		return out_of_memory;
+	}
+	return no_error;
+}
+
+enum cmix_error start_mix(struct CMixContext* ctx, size_t nr_participants) {
+	release_mix(ctx);
+	ctx->nr_participants = nr_participants;
+	return alloc_mix(ctx);
+}
+
+enum cmix_error initialize_mix_randomness(struct CMixContext* ctx) {
+	for(size_t i = 0; i < ctx->nr_participants; ++i) {
+		ctx->r[i] = ctx->api.get_group_element(true);
+		ctx->s[i] = ctx->api.get_group_element(true);
+		ctx->permutation[i] = i;
+	}
+	return no_error;
+}
+
+size_t get_group_element_array_size(struct CMixContext const* ctx) {
+	return ctx->api.get_group_element_array_size();
+}
+
+enum cmix_error set_network_key(struct CMixContext* ctx, char const* buffer, size_t len) {
+	ctx->network_key = ctx->api.array_to_element(buffer, len, true);
+	return no_error;
+}
+
+enum cmix_error encrypt_r(struct CMixContext const* ctx, char* random_buffer, char* message_buffer, size_t index) {
+	GroupElement random_element;
+	GroupElement message_element;
+	
+	ctx->api.encrypt(&random_element, &message_element, ctx->r[index], ctx->network_key);
+	
+	element_to_buffer(ctx, random_buffer, random_element);
+	element_to_buffer(ctx, message_buffer, message_element);
+	
+	return no_error;
+}
+
+enum cmix_error encrypt_r_and_multiply(struct CMixContext const* ctx, char* random_buffer, char* message_buffer, const char* random_element, const char* message_element, size_t index) {
+	GroupElement enc_random_element;
+	GroupElement enc_message_element;
+	
+	ctx->api.encrypt(&enc_random_element, &enc_message_element, ctx->r[index], ctx->network_key);
+	
+	size_t el_size = get_group_element_array_size(ctx);
+	
+	GroupElement other_random_element = ctx->api.array_to_element(random_element, el_size, true);
+	GroupElement other_message_element = ctx->api.array_to_element(message_element, el_size, true);
+	
+	GroupElement new_random_element = ctx->api.multiply(enc_random_element, other_random_element, true);
+	GroupElement new_message_element = ctx->api.multiply(enc_message_element, other_message_element, true);
+	
+	element_to_buffer(ctx, random_buffer, new_random_element);
+	element_to_buffer(ctx, message_buffer, new_message_element);
+		
+	ctx->api.free_group_element(enc_random_element);
+	ctx->api.free_group_element(enc_message_element);
+	ctx->api.free_group_element(other_random_element);
+	ctx->api.free_group_element(other_message_element);
+	ctx->api.free_group_element(new_random_element);
+	ctx->api.free_group_element(new_message_element);
+	
+	return no_error;
+}
+
+enum cmix_error multiply_s(struct CMixContext const* ctx, char* r_out_buffer, char* m_out_buffer, char const* r_in_buffer, char const* m_in_buffer, size_t index) {
+	size_t el_size = get_group_element_array_size(ctx);
+	
+	GroupElement random_r = ctx->api.array_to_element(r_in_buffer, el_size, true);
+	GroupElement message_r = ctx->api.array_to_element(m_in_buffer, el_size, true);
+	
+	GroupElement random_s;
+	GroupElement message_s;
+	
+	ctx->api.encrypt(&random_s, &message_s, ctx->s[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);
+	
+	element_to_buffer(ctx, r_out_buffer, random_pirs);
+	element_to_buffer(ctx, m_out_buffer, message_pirs);
+	
+	ctx->api.free_group_element(random_r);
+	ctx->api.free_group_element(message_r);
+	ctx->api.free_group_element(random_s);
+	ctx->api.free_group_element(message_s);
+	
+	return no_error;
+}
+
+enum cmix_error key_exchange(struct CMixContext const* ctx, GroupElement* shared_key, char* public_key_buffer, char* exchange_value_buffer, char const* pubkey, char const* value) {
+	GroupElement priv_el = ctx->api.get_group_element(true);
+	GroupElement ex_val = ctx->api.get_key_exchange_value(priv_el);
+	
+	size_t el_len = get_group_element_array_size(ctx);
+	
+	*shared_key = ctx->api.derive_shared_key(ctx->keypair, (unsigned char*)pubkey, el_len, (unsigned char*)value, el_len, priv_el, true);
+	
+	element_to_buffer(ctx, public_key_buffer, ctx->keypair.pub);
+	element_to_buffer(ctx, exchange_value_buffer, ex_val);
+	
+	ctx->api.free_group_element(priv_el);
+	ctx->api.free_group_element(ex_val);
+	
+	return no_error;
+}