Diffie Hellman - Revision history

Matt: /* Working with Parameters and Generating Keys */

2021-02-13T14:34:57Z

Working with Parameters and Generating Keys

2021-02-13T14:29:39Z

Undo revision 3139 by L.Habib (talk)

2021-02-12T22:44:58Z

Working with Parameters and Generating Keys

2021-02-12T22:43:24Z

Working with Parameters and Generating Keys

2020-10-09T03:42:37Z

Diffie-Hellman Standards

2015-03-05T23:38:20Z

Corrected example for DH_compute_key to show correct secret size usage

2014-01-21T19:08:20Z

Updated following comments from Dave Thompson on openssl-users list

2013-10-13T18:21:38Z

Spelling correction

2013-10-13T10:54:25Z

Added info on call to SSL_get_peer_certificate.

2013-10-13T10:49:52Z

Added info on the Diffie-Hellman schemes used by SSL/TLS; Formatting

@@ Line 46: / Line 46: @@
 <pre>/* Use built-in parameters */
 if(NULL == (params = EVP_PKEY_new())) handleErrors();
-if(1 != EVP_PKEY_set1_DH(params,DH_get_2048_256())) handleErrors();
+if(1 != EVP_PKEY_assign(params, EVP_PKEY_DHX, DH_get_2048_256())) handleErrors();
 /* Create context for the key generation */

@@ Line 47: / Line 47: @@
 if(NULL == (params = EVP_PKEY_new())) handleErrors();
 if(1 != EVP_PKEY_set1_DH(params,DH_get_2048_256())) handleErrors();
 /* Create context for the key generation */

@@ Line 54: / Line 54: @@
 /* Generate a new key */
 if(1 != EVP_PKEY_keygen_init(kctx)) handleErrors();
-if(1 != EVP_PKEY_keygen(kctx, &dhkey)) handleErrors();</pre>
+if(1 != EVP_PKEY_keygen(kctx, &dhkey)) handleErrors();
 To generate your own parameters refer to [[EVP Key and Parameter Generation]].

@@ Line 47: / Line 47: @@
 if(NULL == (params = EVP_PKEY_new())) handleErrors();
 if(1 != EVP_PKEY_set1_DH(params,DH_get_2048_256())) handleErrors();
 /* Create context for the key generation */

@@ Line 19: / Line 19: @@
 * ANSI X9.42 is a later standard than PKCS 3 and provides further guidance on its use (note OpenSSL does not support ANSI X9.42 in the released versions - support is available in the as yet unreleased 1.0.2 and 1.1.0)
 * [http://www.ietf.org/rfc/rfc2631.txt RFC 2631] summarizes the key points of ANSI X9.42
-* [http://www.ietf.org/rfc/rfc5114 RFC 5114] defines 3 standard sets of parameters for use with Diffie-Hellman (OpenSSL will have built-in support for these parameters from OpenSSL 1.0.2 - not yet released)
+* [http://www.ietf.org/rfc/rfc5114.txt RFC 5114] defines 3 standard sets of parameters for use with Diffie-Hellman (OpenSSL will have built-in support for these parameters from OpenSSL 1.0.2 - not yet released)
 * [http://csrc.nist.gov/publications/nistpubs/800-56A/SP800-56A_Revision1_Mar08-2007.pdf NIST SP 800-56A] is a NIST publication that provides recommendations on the implementation of X9.42

@@ Line 102: / Line 102: @@
 /* Do something with the shared secret */
 printf("The shared secret is:\n");
-BIO_dump_fp(stdout, secret, DH_size(privkey));
+BIO_dump_fp(stdout, secret, secret_size);
 /* Clean up */

@@ Line 73: / Line 73: @@
 /* Generate the parameters to be used */
 if(NULL == (privkey = DH_new())) handleErrors();
-if(1 != DH_generate_parameters_ex(privkey, 1024, DH_GENERATOR_2, NULL)) handleErrors();
+if(1 != DH_generate_parameters_ex(privkey, 2048, DH_GENERATOR_2, NULL)) handleErrors();
 if(1 != DH_check(privkey, &codes)) handleErrors();
@@ Line 87: / Line 87: @@
 if(1 != DH_generate_key(privkey)) handleErrors();
-/* Send the public key to the peer. In this example we just write it out to a file */
+/* Send the public key to the peer.
-BIO *bp = NULL;
+ * How this occurs will be specific to your situation (see main text below) */
-if(NULL == (bp = BIO_new_file("out.dhparams", "wb"))) handleErrors();
 /* Receive the public key from the peer. In this example we're just hard coding a value */
@@ Line 113: / Line 111: @@
 </pre>
 ==See also==

@@ Line 30: / Line 30: @@
 * Ephemeral Diffie-Hellman
-'''Anonymous Diffie-Hellman''' uses Diffie-Hellman, but without authentication. Because the keys used in the exchange are not authenticated, the protocol is susceptible to Man-in-the-Middle attacks. Note: if you use this scheme, a call to <tt>SSL_get_peer_certificate</tt> will return <tt>NULL</tt> because you have selected an anonymous protocol. This si the only time <tt>SSL_get_peer_certificate</tt> is allowed to return <tt>NULL</tt> under normal circumstances.
+'''Anonymous Diffie-Hellman''' uses Diffie-Hellman, but without authentication. Because the keys used in the exchange are not authenticated, the protocol is susceptible to Man-in-the-Middle attacks. Note: if you use this scheme, a call to <tt>SSL_get_peer_certificate</tt> will return <tt>NULL</tt> because you have selected an anonymous protocol. This is the only time <tt>SSL_get_peer_certificate</tt> is allowed to return <tt>NULL</tt> under normal circumstances.
 You should not use Anonymous Diffie-Hellman. You can prohibit its use in your code by using <tt>"!ADH"</tt> in your call to <tt>SSL_set_cipher_list</tt>.