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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "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 .SH "SYNOPSIS" .IX 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 .PP Deprecated: .PP .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 .SH "DESCRIPTION" .IX Header "DESCRIPTION" \&\fBDH_generate_parameters_ex()\fR generates Diffie-Hellman parameters that can be shared among a group of users, and stores them in the provided \fB\s-1DH\s0\fR structure. The pseudo-random number generator must be seeded before calling it. The parameters generated by \fBDH_generate_parameters_ex()\fR should not be used in signature schemes. .PP \&\fBprime_len\fR is the length in bits of the safe prime to be generated. \&\fBgenerator\fR is a small number > 1, typically 2 or 5. .PP A callback function may be used to provide feedback about the progress of the key generation. If \fBcb\fR is not \fB\s-1NULL\s0\fR, it will be called as described in \fBBN_generate_prime\fR\|(3) while a random prime number is generated, and when a prime has been found, \fBBN_GENCB_call(cb, 3, 0)\fR is called. See \fBBN_generate_prime_ex\fR\|(3) for information on the \fBBN_GENCB_call()\fR function. .PP \&\fBDH_generate_parameters()\fR is similar to \fBDH_generate_prime_ex()\fR but expects an old-style callback function; see \&\fBBN_generate_prime\fR\|(3) for information on the old-style callback. .PP \&\fBDH_check_params()\fR confirms that the \fBp\fR and \fBg\fR are likely enough to be valid. This is a lightweight check, if a more thorough check is needed, use \&\fBDH_check()\fR. The value of \fB*codes\fR is updated with any problems found. If \fB*codes\fR is zero then no problems were found, otherwise the following bits may be set: .IP "\s-1DH_CHECK_P_NOT_PRIME\s0" 4 .IX Item "DH_CHECK_P_NOT_PRIME" The parameter \fBp\fR has been determined to not being an odd prime. Note that the lack of this bit doesn't guarantee that \fBp\fR is a prime. .IP "\s-1DH_NOT_SUITABLE_GENERATOR\s0" 4 .IX Item "DH_NOT_SUITABLE_GENERATOR" The generator \fBg\fR is not suitable. Note that the lack of this bit doesn't guarantee that \fBg\fR is suitable, unless \fBp\fR is known to be a strong prime. .IP "\s-1DH_MODULUS_TOO_LARGE\s0" 4 .IX Item "DH_MODULUS_TOO_LARGE" The modulus is too large. .PP \&\fBDH_check()\fR confirms that the Diffie-Hellman parameters \fBdh\fR are valid. The value of \fB*codes\fR is updated with any problems found. If \fB*codes\fR is zero then no problems were found, otherwise the following bits may be set: .IP "\s-1DH_CHECK_P_NOT_PRIME\s0" 4 .IX Item "DH_CHECK_P_NOT_PRIME" The parameter \fBp\fR is not prime. .IP "\s-1DH_CHECK_P_NOT_SAFE_PRIME\s0" 4 .IX Item "DH_CHECK_P_NOT_SAFE_PRIME" The parameter \fBp\fR is not a safe prime and no \fBq\fR value is present. .IP "\s-1DH_UNABLE_TO_CHECK_GENERATOR\s0" 4 .IX Item "DH_UNABLE_TO_CHECK_GENERATOR" The generator \fBg\fR cannot be checked for suitability. .IP "\s-1DH_NOT_SUITABLE_GENERATOR\s0" 4 .IX Item "DH_NOT_SUITABLE_GENERATOR" The generator \fBg\fR is not suitable. .IP "\s-1DH_CHECK_Q_NOT_PRIME\s0" 4 .IX Item "DH_CHECK_Q_NOT_PRIME" The parameter \fBq\fR is not prime. .IP "\s-1DH_CHECK_INVALID_Q_VALUE\s0" 4 .IX Item "DH_CHECK_INVALID_Q_VALUE" The parameter \fBq\fR is invalid. .IP "\s-1DH_CHECK_INVALID_J_VALUE\s0" 4 .IX Item "DH_CHECK_INVALID_J_VALUE" The parameter \fBj\fR is invalid. .PP \&\fBDH_check_ex()\fR, \fBDH_check_params()\fR and \fBDH_check_pub_key_ex()\fR are similar to \&\fBDH_check()\fR and \fBDH_check_params()\fR respectively, but the error reasons are added to the thread's error queue instead of provided as return values from the function. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBDH_generate_parameters_ex()\fR, \fBDH_check()\fR and \fBDH_check_params()\fR return 1 if the check could be performed, 0 otherwise. .PP \&\fBDH_generate_parameters()\fR returns a pointer to the \s-1DH\s0 structure or \s-1NULL\s0 if the parameter generation fails. .PP \&\fBDH_check_ex()\fR, \fBDH_check_params()\fR and \fBDH_check_pub_key_ex()\fR return 1 if the check is successful, 0 for failed. .PP The error codes can be obtained by \fBERR_get_error\fR\|(3). .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBDH_new\fR\|(3), \fBERR_get_error\fR\|(3), \fBRAND_bytes\fR\|(3), \&\fBDH_free\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" \&\fBDH_generate_parameters()\fR was deprecated in OpenSSL 0.9.8; use \&\fBDH_generate_parameters_ex()\fR instead. .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2000\-2018 The OpenSSL Project Authors. All Rights Reserved. .PP 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>.