Added proper keyexchange for elgamal-gcrypt.

1 files changed, 58 insertions, 11 deletions

diff --git a/libcmix-crypto/elgamal/gcrypt/gcrypt_elgamal.c b/libcmix-crypto/elgamal/gcrypt/gcrypt_elgamal.c
index 113fb95..ac90a51 100644
--- a/libcmix-crypto/elgamal/gcrypt/gcrypt_elgamal.c
+++ b/libcmix-crypto/elgamal/gcrypt/gcrypt_elgamal.c
@@ -43,10 +43,10 @@ void elgamal_initialize(void) {
 	gcry_control (GCRYCTL_RESUME_SECMEM_WARN);
 	gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
 	
-	//leading as specified by libgcrypt
-	char p_hex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
-	char q_hex[] = "008CF83642A709A097B447997640129DA299B1A47D1EB3750BA308B0FE64F5FBD3";
-	char g_hex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
+	//leading 0 as specified by libgcrypt
+	char p_hex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
+	char q_hex[] = "08CF83642A709A097B447997640129DA299B1A47D1EB3750BA308B0FE64F5FBD3";
+	char g_hex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
 	
 	size_t nr_bytes_scanned;
 	gcry_error_t error;
@@ -77,9 +77,12 @@ struct KeyPair elgamal_create_keypair() {
 	gcry_sexp_t priv_key;
 	error = gcry_sexp_build(&priv_key, &parse_error_offset, "(private-key (elg (p %M) (g %M) (y %M) (x %M)))", p, g, y, x);
 	check(error);
-	
+
 	error = gcry_pk_testkey(priv_key);
 	check(error);
+
+	gcry_sexp_release(priv_key);
+	gcry_free(bytes);
 	
 	return (struct KeyPair){
 		x,
@@ -94,8 +97,8 @@ void elgamal_keypair_deleter(struct KeyPair* p) {
 	p->pub = NULL;
 }
 
-void elgamal_get_key_array(unsigned char** buffer, size_t* len, void* pubkey) {
-	gcry_mpi_t mpi = (gcry_mpi_t) pubkey;
+void elgamal_get_key_array(unsigned char** buffer, size_t* len, void* key) {
+	gcry_mpi_t mpi = (gcry_mpi_t) key;
 	
 	gcry_error_t error;
 	
@@ -103,14 +106,41 @@ void elgamal_get_key_array(unsigned char** buffer, size_t* len, void* pubkey) {
 	check(error);
 }
 
+void* elgamal_get_group_element(bool secure) {
+	size_t parse_error_offset;
+	gcry_error_t error;
+	
+	void* bytes = gcry_random_bytes_secure(2048/8, GCRY_VERY_STRONG_RANDOM);
+	gcry_mpi_t a = secure ? gcry_mpi_snew(2048) : gcry_mpi_new(2048);
+	error = gcry_mpi_scan(&a, GCRYMPI_FMT_USG, bytes, 2048/8, &parse_error_offset);
+	check(error);
+	
+	gcry_free(bytes);
+	
+	return a;
+}
+
+void elgamal_free_group_element(void* el) {
+	gcry_mpi_release((gcry_mpi_t) el);
+}
+
+void* elgamal_get_key_exchange_value(void* group_el) {
+	gcry_mpi_t el = (gcry_mpi_t) group_el;
+	
+	gcry_mpi_t val = gcry_mpi_new(0);
+	gcry_mpi_powm(val, g, el, p);
+	
+	return val;
+}
+
 void elgamal_add_public_share(char** buffer, size_t* out_len, char const* share, size_t in_len, void* pubkey) {
 	
 	gcry_error_t error;
+	size_t parse_error_pos;
 	
 	gcry_mpi_t y = (gcry_mpi_t) pubkey;
 	
 	gcry_mpi_t mpi_share;
-	size_t parse_error_pos;
 	error = gcry_mpi_scan(&mpi_share, GCRYMPI_FMT_USG, share, in_len, &parse_error_pos);
 	check(error);
 	
@@ -126,12 +156,29 @@ void elgamal_shared_key_deleter(struct SharedKey* s) {
 	s->shared = NULL;
 }
 
-struct SharedKey elgamal_derive_shared_key(struct KeyPair pair, void const* pub_key, bool swap_pub_order) {
+
+struct SharedKey elgamal_derive_shared_key(struct KeyPair keypair, unsigned char const* other_pub, size_t pub_len, unsigned char const* value, size_t value_len, void* priv_value, bool swap) {
+
+	gcry_error_t error;
+	size_t parse_error_pos;
+
+	gcry_mpi_t ga;
+	error = gcry_mpi_scan(&ga, GCRYMPI_FMT_USG, value, value_len, &parse_error_pos);
+	check(error);
 	
+	gcry_mpi_t b = (gcry_mpi_t) priv_value;
+	gcry_mpi_t gab = gcry_mpi_snew(0);
+	gcry_mpi_powm(gab, ga, b, p);
+
+	gcry_mpi_release(ga);
 
 	return (struct SharedKey){
-		NULL,
+		gab
 	};
 }
 
-void elgamal_deinitialize(void) {}
+void elgamal_deinitialize(void) {
+	gcry_mpi_release(p);
+	gcry_mpi_release(q);
+	gcry_mpi_release(g);
+}