Updated: 2021/Apr/14


DH_generate_parameters(3)           OpenSSL          DH_generate_parameters(3)



NAME
       DH_generate_parameters_ex, DH_generate_parameters, DH_check,
       DH_check_params, DH_check_ex, DH_check_params_ex, DH_check_pub_key_ex -
       generate and check Diffie-Hellman parameters

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #include <openssl/dh.h>

        int DH_generate_parameters_ex(DH *dh, int prime_len, int generator, BN_GENCB *cb);

        int DH_check(DH *dh, int *codes);
        int DH_check_params(DH *dh, int *codes);

        int DH_check_ex(const DH *dh);
        int DH_check_params_ex(const DH *dh);
        int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key);

       Deprecated:

        #if OPENSSL_API_COMPAT < 0x00908000L
        DH *DH_generate_parameters(int prime_len, int generator,
                                   void (*callback)(int, int, void *), void *cb_arg);
        #endif

DESCRIPTION
       DH_generate_parameters_ex() generates Diffie-Hellman parameters that
       can be shared among a group of users, and stores them in the provided
       DH structure. The pseudo-random number generator must be seeded before
       calling it.  The parameters generated by DH_generate_parameters_ex()
       should not be used in signature schemes.

       prime_len is the length in bits of the safe prime to be generated.
       generator is a small number > 1, typically 2 or 5.

       A callback function may be used to provide feedback about the progress
       of the key generation. If cb is not NULL, it will be called as
       described in BN_generate_prime(3) while a random prime number is
       generated, and when a prime has been found, BN_GENCB_call(cb, 3, 0) is
       called. See BN_generate_prime_ex(3) for information on the
       BN_GENCB_call() function.

       DH_generate_parameters() is similar to DH_generate_prime_ex() but
       expects an old-style callback function; see BN_generate_prime(3) for
       information on the old-style callback.

       DH_check_params() confirms that the p and g are likely enough to be
       valid.  This is a lightweight check, if a more thorough check is
       needed, use DH_check().  The value of *codes is updated with any
       problems found.  If *codes is zero then no problems were found,
       otherwise the following bits may be set:

       DH_CHECK_P_NOT_PRIME
           The parameter p has been determined to not being an odd prime.
           Note that the lack of this bit doesn't guarantee that p is a prime.

       DH_NOT_SUITABLE_GENERATOR
           The generator g is not suitable.  Note that the lack of this bit
           doesn't guarantee that g is suitable, unless p is known to be a
           strong prime.

       DH_check() confirms that the Diffie-Hellman parameters dh are valid.
       The value of *codes is updated with any problems found. If *codes is
       zero then no problems were found, otherwise the following bits may be
       set:

       DH_CHECK_P_NOT_PRIME
           The parameter p is not prime.

       DH_CHECK_P_NOT_SAFE_PRIME
           The parameter p is not a safe prime and no q value is present.

       DH_UNABLE_TO_CHECK_GENERATOR
           The generator g cannot be checked for suitability.

       DH_NOT_SUITABLE_GENERATOR
           The generator g is not suitable.

       DH_CHECK_Q_NOT_PRIME
           The parameter q is not prime.

       DH_CHECK_INVALID_Q_VALUE
           The parameter q is invalid.

       DH_CHECK_INVALID_J_VALUE
           The parameter j is invalid.

       DH_check_ex(), DH_check_params() and DH_check_pub_key_ex() are similar
       to DH_check() and DH_check_params() respectively, but the error reasons
       are added to the thread's error queue instead of provided as return
       values from the function.

RETURN VALUES
       DH_generate_parameters_ex(), DH_check() and DH_check_params() return 1
       if the check could be performed, 0 otherwise.

       DH_generate_parameters() returns a pointer to the DH structure or NULL
       if the parameter generation fails.

       DH_check_ex(), DH_check_params() and DH_check_pub_key_ex() return 1 if
       the check is successful, 0 for failed.

       The error codes can be obtained by ERR_get_error(3).

SEE ALSO
       DH_new(3), ERR_get_error(3), RAND_bytes(3), DH_free(3)

HISTORY
       DH_generate_parameters() was deprecated in OpenSSL 0.9.8; use
       DH_generate_parameters_ex() instead.

COPYRIGHT
       Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.



1.1.1i                            2018-09-23         DH_generate_parameters(3)