1DH_GENERATE_PARAMETERS(3ossl)       OpenSSL      DH_GENERATE_PARAMETERS(3ossl)
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NAME

6       DH_generate_parameters_ex, DH_generate_parameters, DH_check,
7       DH_check_params, DH_check_ex, DH_check_params_ex, DH_check_pub_key_ex -
8       generate and check Diffie-Hellman parameters
9

SYNOPSIS

11        #include <openssl/dh.h>
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13       The following functions have been deprecated since OpenSSL 3.0, and can
14       be hidden entirely by defining OPENSSL_API_COMPAT with a suitable
15       version value, see openssl_user_macros(7):
16
17        int DH_generate_parameters_ex(DH *dh, int prime_len, int generator, BN_GENCB *cb);
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19        int DH_check(DH *dh, int *codes);
20        int DH_check_params(DH *dh, int *codes);
21
22        int DH_check_ex(const DH *dh);
23        int DH_check_params_ex(const DH *dh);
24        int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key);
25
26       The following functions have been deprecated since OpenSSL 0.9.8, and
27       can be hidden entirely by defining OPENSSL_API_COMPAT with a suitable
28       version value, see openssl_user_macros(7):
29
30        DH *DH_generate_parameters(int prime_len, int generator,
31                                   void (*callback)(int, int, void *), void *cb_arg);
32

DESCRIPTION

34       All of the functions described on this page are deprecated.
35       Applications should instead use EVP_PKEY_check(3),
36       EVP_PKEY_public_check(3), EVP_PKEY_private_check(3) and
37       EVP_PKEY_param_check(3).
38
39       DH_generate_parameters_ex() generates Diffie-Hellman parameters that
40       can be shared among a group of users, and stores them in the provided
41       DH structure. The pseudo-random number generator must be seeded before
42       calling it.  The parameters generated by DH_generate_parameters_ex()
43       should not be used in signature schemes.
44
45       prime_len is the length in bits of the safe prime to be generated.
46       generator is a small number > 1, typically 2 or 5.
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48       A callback function may be used to provide feedback about the progress
49       of the key generation. If cb is not NULL, it will be called as
50       described in BN_generate_prime(3) while a random prime number is
51       generated, and when a prime has been found, BN_GENCB_call(cb, 3, 0) is
52       called. See BN_generate_prime_ex(3) for information on the
53       BN_GENCB_call() function.
54
55       DH_generate_parameters() is similar to DH_generate_prime_ex() but
56       expects an old-style callback function; see BN_generate_prime(3) for
57       information on the old-style callback.
58
59       DH_check_params() confirms that the p and g are likely enough to be
60       valid.  This is a lightweight check, if a more thorough check is
61       needed, use DH_check().  The value of *codes is updated with any
62       problems found.  If *codes is zero then no problems were found,
63       otherwise the following bits may be set:
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65       DH_CHECK_P_NOT_PRIME
66           The parameter p has been determined to not being an odd prime.
67           Note that the lack of this bit doesn't guarantee that p is a prime.
68
69       DH_NOT_SUITABLE_GENERATOR
70           The generator g is not suitable.  Note that the lack of this bit
71           doesn't guarantee that g is suitable, unless p is known to be a
72           strong prime.
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74       DH_MODULUS_TOO_SMALL
75           The modulus is too small.
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77       DH_MODULUS_TOO_LARGE
78           The modulus is too large.
79
80       DH_check() confirms that the Diffie-Hellman parameters dh are valid.
81       The value of *codes is updated with any problems found. If *codes is
82       zero then no problems were found, otherwise the following bits may be
83       set:
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85       DH_CHECK_P_NOT_PRIME
86           The parameter p is not prime.
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88       DH_CHECK_P_NOT_SAFE_PRIME
89           The parameter p is not a safe prime and no q value is present.
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91       DH_UNABLE_TO_CHECK_GENERATOR
92           The generator g cannot be checked for suitability.
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94       DH_NOT_SUITABLE_GENERATOR
95           The generator g is not suitable.
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97       DH_CHECK_Q_NOT_PRIME
98           The parameter q is not prime.
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100       DH_CHECK_INVALID_Q_VALUE
101           The parameter q is invalid.
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103       DH_CHECK_INVALID_J_VALUE
104           The parameter j is invalid.
105
106       DH_check_ex(), DH_check_params() and DH_check_pub_key_ex() are similar
107       to DH_check() and DH_check_params() respectively, but the error reasons
108       are added to the thread's error queue instead of provided as return
109       values from the function.
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RETURN VALUES

112       DH_generate_parameters_ex(), DH_check() and DH_check_params() return 1
113       if the check could be performed, 0 otherwise.
114
115       DH_generate_parameters() returns a pointer to the DH structure or NULL
116       if the parameter generation fails.
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118       DH_check_ex(), DH_check_params() and DH_check_pub_key_ex() return 1 if
119       the check is successful, 0 for failed.
120
121       The error codes can be obtained by ERR_get_error(3).
122

SEE ALSO

124       DH_new(3), ERR_get_error(3), RAND_bytes(3), DH_free(3)
125

HISTORY

127       All of these functions were deprecated in OpenSSL 3.0.
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129       DH_generate_parameters() was deprecated in OpenSSL 0.9.8; use
130       DH_generate_parameters_ex() instead.
131

133       Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
134
135       Licensed under the Apache License 2.0 (the "License").  You may not use
136       this file except in compliance with the License.  You can obtain a copy
137       in the file LICENSE in the source distribution or at
138       <https://www.openssl.org/source/license.html>.
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1423.0.5                             2022-07-05     DH_GENERATE_PARAMETERS(3ossl)
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