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Title "DH_GENERATE_PARAMETERS 3" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
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 Header "SYNOPSIS" .Vb 1 #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); .Ve

Deprecated:

.Vb 4 #if OPENSSL_API_COMPAT < 0x00908000L DH *DH_generate_parameters(int prime_len, int generator, void (*callback)(int, int, void *), void *cb_arg); #endif .Ve

Header "DESCRIPTION" \fBDH_generate_parameters_ex() generates Diffie-Hellman parameters that can be shared among a group of users, and stores them in the provided \s-1DH\s0 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.

\fBprime_len is the length in bits of the safe prime to be generated. \fBgenerator 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 \s-1NULL\s0, 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.

\fBDH_generate_parameters() is similar to DH_generate_prime_ex() but expects an old-style callback function; see \fBBN_generate_prime\|(3) for information on the old-style callback.

\fBDH_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 \fBDH_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:

Item "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. Item "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.

\fBDH_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:

Item "DH_CHECK_P_NOT_PRIME" The parameter p is not prime. Item "DH_CHECK_P_NOT_SAFE_PRIME" The parameter p is not a safe prime and no q value is present. Item "DH_UNABLE_TO_CHECK_GENERATOR" The generator g cannot be checked for suitability. Item "DH_NOT_SUITABLE_GENERATOR" The generator g is not suitable. Item "DH_CHECK_Q_NOT_PRIME" The parameter q is not prime. Item "DH_CHECK_INVALID_Q_VALUE" The parameter q is invalid. Item "DH_CHECK_INVALID_J_VALUE" The parameter j is invalid.

\fBDH_check_ex(), DH_check_params() and DH_check_pub_key_ex() are similar to \fBDH_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.

Header "RETURN VALUES" \fBDH_generate_parameters_ex(), DH_check() and DH_check_params() return 1 if the check could be performed, 0 otherwise.

\fBDH_generate_parameters() returns a pointer to the \s-1DH\s0 structure or \s-1NULL\s0 if the parameter generation fails.

\fBDH_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).

Header "SEE ALSO" \fBDH_new\|(3), ERR_get_error\|(3), RAND_bytes\|(3), \fBDH_free\|(3) Header "HISTORY" \fBDH_generate_parameters() was deprecated in OpenSSL 0.9.8; use \fBDH_generate_parameters_ex() instead. Header "COPYRIGHT" Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.