Add documentation for following DH and DH_METHOD opacity

[openssl.git] / doc / crypto / dh.pod

diff --git a/doc/crypto/dh.pod b/doc/crypto/dh.pod
index d364da48fd7cb4feca10f65a94661cdbdd4f4ef3..b1eaa480b7e281c5f2980391ebe92ca34fa3fd3c 100644 (file)
--- a/doc/crypto/dh.pod
+++ b/doc/crypto/dh.pod
@@ -7,35 +7,29 @@ dh - Diffie-Hellman key agreement
 =head1 SYNOPSIS
 
  #include <openssl/dh.h>
-
- void DH_set_default_method(DH_METHOD *meth);
- DH_METHOD *DH_get_default_method(void);
- DH_METHOD *DH_set_method(DH *dh, DH_METHOD *meth);
- DH *DH_new_method(DH_METHOD *meth);
- DH_METHOD *DH_OpenSSL(void);
+ #include <openssl/engine.h>
 
  DH *  DH_new(void);
  void  DH_free(DH *dh);
 
- int   DH_size(DH *dh);
-
- int DH_get_ex_new_index(long argl, char *argp, int (*new_func)(),
-            int (*dup_func)(), void (*free_func)());
- int DH_set_ex_data(DH *d, int idx, char *arg);
- char *DH_get_ex_data(DH *d, int idx);
-
  DH *  DH_generate_parameters(int prime_len, int generator,
                void (*callback)(int, int, void *), void *cb_arg);
- int   DH_check(DH *dh, int *codes);
+ int   DH_check(const DH *dh, int *codes);
 
  int   DH_generate_key(DH *dh);
  int   DH_compute_key(unsigned char *key, BIGNUM *pub_key, DH *dh);
 
+ void DH_set_default_method(const DH_METHOD *meth);
+ const DH_METHOD *DH_get_default_method(void);
+ int DH_set_method(DH *dh, const DH_METHOD *meth);
+ DH *DH_new_method(ENGINE *engine);
+ const DH_METHOD *DH_OpenSSL(void);
+
  DH *  d2i_DHparams(DH **a, unsigned char **pp, long length);
- int   i2d_DHparams(DH *a, unsigned char **pp);
+ int   i2d_DHparams(const DH *a, unsigned char **pp);
 
- int   DHparams_print_fp(FILE *fp, DH *x);
- int   DHparams_print(BIO *bp, DH *x);
+ int   DHparams_print_fp(FILE *fp, const DH *x);
+ int   DHparams_print(BIO *bp, const DH *x);
 
 =head1 DESCRIPTION
 
@@ -44,22 +38,24 @@ The generation of shared DH parameters is described in
 L<DH_generate_parameters(3)>; L<DH_generate_key(3)> describes how
 to perform a key agreement.
 
-The B<DH> structure consists of several BIGNUM components.
+The B<DH> structure consists of several BIGNUM components. The prime B<p>, the
+generate B<g>, the Private key B<priv_key> and the public key B<pub_key>.
+Optionally there may also be an additional parameter B<q>.
 
- struct
-        {
-        BIGNUM *p;             // prime number (shared)
-        BIGNUM *g;             // generator of Z_p (shared)
-        BIGNUM *priv_key;      // private DH value x
-        BIGNUM *pub_key;       // public DH value g^x
-       // ...
-        };
- DH
+Note that DH keys may use non-standard B<DH_METHOD> implementations,
+either directly or by the use of B<ENGINE> modules. In some cases (eg. an
+ENGINE providing support for hardware-embedded keys), these BIGNUM values
+will not be used by the implementation or may be used for alternative data
+storage.
 
 =head1 SEE ALSO
 
-dh(1), bn(3), dsa(3), err(3), rand(3), rsa(3), DH_set_method(3),
-DH_new(3), DH_get_ex_new_index(3), DH_generate_parameters(3),
-DH_compute_key(3), d2i_DHparams(3), DHparams_print(3)
+L<dhparam(1)>, L<bn(3)>, L<dsa(3)>, L<err(3)>,
+L<rand(3)>, L<rsa(3)>, L<engine(3)>,
+L<DH_set_method(3)>, L<DH_new(3)>,
+L<DH_get_ex_new_index(3)>,
+L<DH_generate_parameters(3)>,
+L<DH_compute_key(3)>, L<DH_get0_pqg(3)>, L<DH_meth_new(3)>, L<d2i_DHparams(3)>,
+L<RSA_print(3)> 
 
 =cut