1 files changed, 78 insertions, 0 deletions
diff --git a/doc/crypto/dh.pod b/doc/crypto/dh.pod
new file mode 100644
index 000000000000..c3ccd0620783
--- /dev/null
+++ b/doc/crypto/dh.pod
@@ -0,0 +1,78 @@
+=pod
+
+=head1 NAME
+
+dh - Diffie-Hellman key agreement
+
+=head1 SYNOPSIS
+
+ #include <openssl/dh.h>
+ #include <openssl/engine.h>
+
+ DH *	DH_new(void);
+ void	DH_free(DH *dh);
+
+ int	DH_size(const DH *dh);
+
+ DH *	DH_generate_parameters(int prime_len, int generator,
+		void (*callback)(int, int, void *), void *cb_arg);
+ 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);
+
+ 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 *	d2i_DHparams(DH **a, unsigned char **pp, long length);
+ int	i2d_DHparams(const DH *a, unsigned char **pp);
+
+ int	DHparams_print_fp(FILE *fp, const DH *x);
+ int	DHparams_print(BIO *bp, const DH *x);
+
+=head1 DESCRIPTION
+
+These functions implement the Diffie-Hellman key agreement protocol.
+The generation of shared DH parameters is described in
+L<DH_generate_parameters(3)|DH_generate_parameters(3)>; L<DH_generate_key(3)|DH_generate_key(3)> describes how
+to perform a key agreement.
+
+The B<DH> structure consists of several BIGNUM components.
+
+ 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. For this reason, applications should generally avoid using DH
+structure elements directly and instead use API functions to query or
+modify keys.
+
+=head1 SEE ALSO
+
+L<dhparam(1)|dhparam(1)>, L<bn(3)|bn(3)>, L<dsa(3)|dsa(3)>, L<err(3)|err(3)>,
+L<rand(3)|rand(3)>, L<rsa(3)|rsa(3)>, L<engine(3)|engine(3)>,
+L<DH_set_method(3)|DH_set_method(3)>, L<DH_new(3)|DH_new(3)>,
+L<DH_get_ex_new_index(3)|DH_get_ex_new_index(3)>,
+L<DH_generate_parameters(3)|DH_generate_parameters(3)>,
+L<DH_compute_key(3)|DH_compute_key(3)>, L<d2i_DHparams(3)|d2i_DHparams(3)>,
+L<RSA_print(3)|RSA_print(3)> 
+
+=cut