--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/dh/dh_import.c	Fri Feb 09 21:44:05 2018 +0800
@@ -0,0 +1,99 @@
+/* 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
+
+/**
+  Import a DH key from a binary packet
+  @param in     The packet to read
+  @param inlen  The length of the input packet
+  @param key    [out] Where to import the key to
+  @return CRYPT_OK if successful, on error all allocated memory is freed automatically
+*/
+int dh_import(const unsigned char *in, unsigned long inlen, dh_key *key)
+{
+   unsigned char flags[1];
+   int err;
+   unsigned long version;
+
+   LTC_ARGCHK(in  != NULL);
+   LTC_ARGCHK(key != NULL);
+
+   /* init */
+   if ((err = mp_init_multi(&key->x, &key->y, &key->base, &key->prime, NULL)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* find out what type of key it is */
+   err = der_decode_sequence_multi(in, inlen,
+                                   LTC_ASN1_SHORT_INTEGER, 1UL, &version,
+                                   LTC_ASN1_BIT_STRING, 1UL, &flags,
+                                   LTC_ASN1_EOL, 0UL, NULL);
+   if (err != CRYPT_OK && err != CRYPT_INPUT_TOO_LONG) {
+      goto error;
+   }
+
+   if (version == 0) {
+      if (flags[0] == 1) {
+         key->type = PK_PRIVATE;
+         if ((err = der_decode_sequence_multi(in, inlen,
+                                              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)) != CRYPT_OK) {
+            goto error;
+         }
+         /* compute public key: y = (base ^ x) mod prime */
+         if ((err = mp_exptmod(key->base, key->x, key->prime, key->y)) != CRYPT_OK) {
+            goto error;
+         }
+      }
+      else if (flags[0] == 0) {
+         key->type = PK_PUBLIC;
+         if ((err = der_decode_sequence_multi(in, inlen,
+                                              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)) != CRYPT_OK) {
+            goto error;
+         }
+      }
+      else {
+         err = CRYPT_INVALID_PACKET;
+         goto error;
+      }
+   }
+   else {
+      err = CRYPT_INVALID_PACKET;
+      goto error;
+   }
+
+   /* check public key */
+   if ((err = dh_check_pubkey(key)) != CRYPT_OK) {
+      goto error;
+   }
+
+   return CRYPT_OK;
+
+error:
+   dh_free(key);
+   return err;
+}
+
+#endif /* LTC_MDH */
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */