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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
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5 | |
6 | DH_generate_parameters_ex, DH_generate_parameters, | |
7 | DH_check - generate and check Diffie-Hellman parameters | |
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8 | |
9 | =head1 SYNOPSIS | |
10 | ||
11 | #include <openssl/dh.h> | |
12 | ||
aafbe1cc | 13 | int DH_generate_parameters_ex(DH *dh, int prime_len,int generator, BN_GENCB *cb); |
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14 | |
15 | int DH_check(DH *dh, int *codes); | |
16 | ||
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17 | Deprecated: |
18 | ||
19 | DH *DH_generate_parameters(int prime_len, int generator, | |
20 | void (*callback)(int, int, void *), void *cb_arg); | |
21 | ||
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22 | =head1 DESCRIPTION |
23 | ||
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24 | DH_generate_parameters_ex() generates Diffie-Hellman parameters that can |
25 | be shared among a group of users, and stores them in the provided B<DH> | |
26 | structure. The pseudo-random number generator must be | |
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27 | seeded prior to calling DH_generate_parameters(). |
28 | ||
29 | B<prime_len> is the length in bits of the safe prime to be generated. | |
30 | B<generator> is a small number E<gt> 1, typically 2 or 5. | |
31 | ||
32 | A callback function may be used to provide feedback about the progress | |
aafbe1cc | 33 | of the key generation. If B<cb> is not B<NULL>, it will be |
9b86974e | 34 | called as described in L<BN_generate_prime(3)> while a random prime |
aafbe1cc | 35 | number is generated, and when a prime has been found, B<BN_GENCB_call(cb, 3, 0)> |
9b86974e | 36 | is called. See L<BN_generate_prime(3)> for information on |
aafbe1cc | 37 | the BN_GENCB_call() function. |
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38 | |
39 | DH_check() validates Diffie-Hellman parameters. It checks that B<p> is | |
40 | a safe prime, and that B<g> is a suitable generator. In the case of an | |
41 | error, the bit flags DH_CHECK_P_NOT_SAFE_PRIME or | |
42 | DH_NOT_SUITABLE_GENERATOR are set in B<*codes>. | |
43 | DH_UNABLE_TO_CHECK_GENERATOR is set if the generator cannot be | |
44 | checked, i.e. it does not equal 2 or 5. | |
45 | ||
46 | =head1 RETURN VALUES | |
47 | ||
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48 | DH_generate_parameters_ex() and DH_check() return 1 if the check could be |
49 | performed, 0 otherwise. | |
50 | ||
51 | DH_generate_parameters() (deprecated) returns a pointer to the DH structure, or | |
52 | NULL if the parameter generation fails. | |
4486d0cd | 53 | |
9b86974e | 54 | The error codes can be obtained by L<ERR_get_error(3)>. |
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55 | |
56 | =head1 NOTES | |
57 | ||
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58 | DH_generate_parameters_ex() and DH_generate_parameters() may run for several |
59 | hours before finding a suitable prime. | |
4486d0cd | 60 | |
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61 | The parameters generated by DH_generate_parameters_ex() and DH_generate_parameters() |
62 | are not to be used in signature schemes. | |
4486d0cd | 63 | |
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64 | =head1 BUGS |
65 | ||
66 | If B<generator> is not 2 or 5, B<dh-E<gt>g>=B<generator> is not | |
67 | a usable generator. | |
68 | ||
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69 | =head1 SEE ALSO |
70 | ||
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71 | L<dh(3)>, L<ERR_get_error(3)>, L<rand(3)>, |
72 | L<DH_free(3)> | |
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73 | |
74 | =head1 HISTORY | |
75 | ||
76 | DH_check() is available in all versions of SSLeay and OpenSSL. | |
77 | The B<cb_arg> argument to DH_generate_parameters() was added in SSLeay 0.9.0. | |
78 | ||
79 | In versions before OpenSSL 0.9.5, DH_CHECK_P_NOT_STRONG_PRIME is used | |
80 | instead of DH_CHECK_P_NOT_SAFE_PRIME. | |
81 | ||
82 | =cut |