diff --git a/sshcryptointerface.h b/sshcryptointerface.h
new file mode 100644
index 0000000..623f781
--- /dev/null
+++ b/sshcryptointerface.h
@@ -0,0 +1,37 @@
+//Initializers
+//openSSL 
+struct sshdh *sshdh_openssl_new(void);
+//ms_cng
+struct sshdh *sshdh_ms_cng_new(void);
+
+//need to think about this one
+struct sshdh *sshdh_new_group(struct sshbn *gen, struct sshbn *modulus);
+
+struct sshdh{
+    //Interface
+    void (*sshdh_free)(struct sshdh *dh);
+    struct sshbn *(*sshdh_pubkey)(struct sshdh *dh);
+    struct sshbn *(*sshdh_p)(struct sshdh *dh);
+    struct sshbn *(*sshdh_g)(struct sshdh *dh);
+    void (*sshdh_dump)(struct sshdh *dh);
+    size_t (*sshdh_shared_key_size)(struct sshdh *dh);
+    int (*sshdh_compute_key)(struct sshdh *dh, struct sshbn *pubkey, struct sshbn **shared_secretp);
+    int (*sshdh_generate)(struct sshdh *dh, size_t len);
+    int (*sshdh_new_group_hex)(const char *gen, const char *modulus, struct sshdh **dhp);
+    //Initializer of sshbn done in the context of a sshdh. 
+    struct sshbn *(*sshbn_new)();
+};
+
+struct sshbn {
+    void (*sshbn_free)(struct sshbn *bn);
+    int (*sshbn_from)(const void *d, size_t l, struct sshbn **retp);
+    int (*sshbn_from_hex)(const char *hex, struct sshbn **retp);
+    size_t (*sshbn_bits)(const struct sshbn *bn);
+    const struct sshbn *(*sshbn_value_0)(void);
+    const struct sshbn *(*sshbn_value_1)(void);
+    int (*sshbn_is_bit_set)(const struct sshbn *bn, size_t i);
+
+    //TODO: enforce that multiple sshbn instances involved are from the same implementation. 
+    int sshbn_cmp(const struct sshbn *b);
+    int sshbn_sub(struct sshbn *r, const struct sshbn *b);
+};
\ No newline at end of file