--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/dh/dh_export.c	Fri Feb 09 21:44:05 2018 +0800
@@ -0,0 +1,62 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ */
+
+#include "tomcrypt.h"
+
+#ifdef LTC_MDH
+
+/**
+  Export a DH key to a binary packet
+  @param out    [out] The destination for the key
+  @param outlen [in/out] The max size and resulting size of the DH key
+  @param type   Which type of key (PK_PRIVATE or PK_PUBLIC)
+  @param key    The key you wish to export
+  @return CRYPT_OK if successful
+*/
+int dh_export(unsigned char *out, unsigned long *outlen, int type, dh_key *key)
+{
+   unsigned char flags[1];
+   int err;
+   unsigned long version = 0;
+
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+   LTC_ARGCHK(key    != NULL);
+
+   if (type == PK_PRIVATE) {
+      /* export x - private key */
+      flags[0] = 1;
+      err = der_encode_sequence_multi(out, outlen,
+                                LTC_ASN1_SHORT_INTEGER, 1UL, &version,
+                                LTC_ASN1_BIT_STRING,    1UL, flags,
+                                LTC_ASN1_INTEGER,       1UL, key->prime,
+                                LTC_ASN1_INTEGER,       1UL, key->base,
+                                LTC_ASN1_INTEGER,       1UL, key->x,
+                                LTC_ASN1_EOL,           0UL, NULL);
+   }
+   else {
+      /* export y - public key */
+      flags[0] = 0;
+      err = der_encode_sequence_multi(out, outlen,
+                                LTC_ASN1_SHORT_INTEGER, 1UL, &version,
+                                LTC_ASN1_BIT_STRING,    1UL, flags,
+                                LTC_ASN1_INTEGER,       1UL, key->prime,
+                                LTC_ASN1_INTEGER,       1UL, key->base,
+                                LTC_ASN1_INTEGER,       1UL, key->y,
+                                LTC_ASN1_EOL,           0UL, NULL);
+   }
+
+   return err;
+}
+
+#endif /* LTC_MDH */
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */