1 files changed, 51 insertions, 4 deletions
diff --git a/libcmix-crypto/curve25519/sodium/libsodium_curve25519.c b/libcmix-crypto/curve25519/sodium/libsodium_curve25519.c
index 8fd087a..59e9258 100644
--- a/libcmix-crypto/curve25519/sodium/libsodium_curve25519.c
+++ b/libcmix-crypto/curve25519/sodium/libsodium_curve25519.c
@@ -12,9 +12,12 @@ void init() {
 	}
 }
 
-void sodium_curve25519_keypair_deleter(struct KeyPair* p) {
-	sodium_free(p->sec);
-	free(p->pub);
+void curve25519_keypair_deleter(struct KeyPair p) {
+	sodium_free(p.sec);
+	free(p.pub);
+
+	p.sec = NULL;
+	p.pub = NULL;
 }
 
 struct KeyPair curve25519_create_keypair() {
@@ -26,5 +29,49 @@ struct KeyPair curve25519_create_keypair() {
 	randombytes_buf(sec, crypto_box_SECRETKEYBYTES);
 	crypto_scalarmult_base(pub, sec);
 
-	return (struct KeyPair){sec, pub, crypto_box_SECRETKEYBYTES, crypto_box_PUBLICKEYBYTES, &sodium_curve25519_keypair_deleter};
+	return (struct KeyPair){
+		sec,
+		pub,
+		crypto_box_SECRETKEYBYTES,
+		crypto_box_PUBLICKEYBYTES
+	};
+}
+
+void curve25519_shared_key_deleter(struct SharedKey s) {
+	sodium_free(s.shared);
+
+	s.shared = NULL;
+}
+
+struct SharedKey curve25519_derive_shared_key(struct KeyPair pair, unsigned char* pub_key, bool swap_pub_order) {
+	init();
+
+	unsigned char* shared = (unsigned char*) sodium_malloc(crypto_generichash_BYTES);
+
+	crypto_generichash_state h;
+
+	unsigned char* scalarmult_q = (unsigned char*) sodium_malloc(crypto_scalarmult_BYTES);
+
+	if (crypto_scalarmult(scalarmult_q, pair.sec, pub_key) != 0) {
+		exit(-1);
+	}
+
+	crypto_generichash_init(&h, NULL, 0U, crypto_generichash_BYTES);
+	crypto_generichash_update(&h, scalarmult_q, crypto_scalarmult_BYTES);
+	if(swap_pub_order) {
+		crypto_generichash_update(&h, pub_key, crypto_box_PUBLICKEYBYTES);
+		crypto_generichash_update(&h, pair.pub, crypto_box_PUBLICKEYBYTES);
+	} else {
+		crypto_generichash_update(&h, pair.pub, crypto_box_PUBLICKEYBYTES);
+		crypto_generichash_update(&h, pub_key, crypto_box_PUBLICKEYBYTES);
+	}
+	crypto_generichash_final(&h, shared, crypto_generichash_BYTES);
+
+	sodium_free(scalarmult_q);
+
+	return (struct SharedKey){
+		shared,
+		crypto_generichash_BYTES
+	};
 }
+