Make pk_info_t opaque
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index 207d354..903f9e4 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -136,57 +136,7 @@
 /**
  * \brief           Public key information and operations
  */
-typedef struct
-{
-    /** Public key type */
-    pk_type_t type;
-
-    /** Type name */
-    const char *name;
-
-    /** Get key size in bits */
-    size_t (*get_size)( const void * );
-
-    /** Tell if the context implements this type (e.g. ECKEY can do ECDSA) */
-    int (*can_do)( pk_type_t type );
-
-    /** Verify signature */
-    int (*verify_func)( void *ctx, md_type_t md_alg,
-                        const unsigned char *hash, size_t hash_len,
-                        const unsigned char *sig, size_t sig_len );
-
-    /** Make signature */
-    int (*sign_func)( void *ctx, md_type_t md_alg,
-                      const unsigned char *hash, size_t hash_len,
-                      unsigned char *sig, size_t *sig_len,
-                      int (*f_rng)(void *, unsigned char *, size_t),
-                      void *p_rng );
-
-    /** Decrypt message */
-    int (*decrypt_func)( void *ctx, const unsigned char *input, size_t ilen,
-                         unsigned char *output, size_t *olen, size_t osize,
-                         int (*f_rng)(void *, unsigned char *, size_t),
-                         void *p_rng );
-
-    /** Encrypt message */
-    int (*encrypt_func)( void *ctx, const unsigned char *input, size_t ilen,
-                         unsigned char *output, size_t *olen, size_t osize,
-                         int (*f_rng)(void *, unsigned char *, size_t),
-                         void *p_rng );
-
-    /** Check public-private key pair */
-    int (*check_pair_func)( const void *pub, const void *prv );
-
-    /** Allocate a new context */
-    void * (*ctx_alloc_func)( void );
-
-    /** Free the given context */
-    void (*ctx_free_func)( void *ctx );
-
-    /** Interface with the debug module */
-    void (*debug_func)( const void *ctx, pk_debug_item *items );
-
-} pk_info_t;
+typedef struct _pk_info_t pk_info_t;
 
 /**
  * \brief           Public key container