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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
5 | DSA_sign, DSA_sign_setup, DSA_verify - DSA signatures | |
6 | ||
7 | =head1 SYNOPSIS | |
8 | ||
9 | #include <openssl/dsa.h> | |
10 | ||
11 | int DSA_sign(int type, const unsigned char *dgst, int len, | |
12 | unsigned char *sigret, unsigned int *siglen, DSA *dsa); | |
13 | ||
14 | int DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp, | |
15 | BIGNUM **rp); | |
16 | ||
17 | int DSA_verify(int type, const unsigned char *dgst, int len, | |
18 | unsigned char *sigbuf, int siglen, DSA *dsa); | |
19 | ||
20 | =head1 DESCRIPTION | |
21 | ||
22 | DSA_sign() computes a digital signature on the B<len> byte message | |
23 | digest B<dgst> using the private key B<dsa> and places its ASN.1 DER | |
24 | encoding at B<sigret>. The length of the signature is places in | |
25 | *B<siglen>. B<sigret> must point to DSA_size(B<dsa>) bytes of memory. | |
26 | ||
27 | DSA_sign_setup() may be used to precompute part of the signing | |
28 | operation in case signature generation is time-critical. It expects | |
29 | B<dsa> to contain DSA parameters. It places the precomputed values | |
30 | in newly allocated B<BIGNUM>s at *B<kinvp> and *B<rp>, after freeing | |
31 | the old ones unless *B<kinvp> and *B<rp> are NULL. These values may | |
32 | be passed to DSA_sign() in B<dsa-E<gt>kinv> and B<dsa-E<gt>r>. | |
33 | B<ctx> is a pre-allocated B<BN_CTX> or NULL. | |
34 | ||
35 | DSA_verify() verifies that the signature B<sigbuf> of size B<siglen> | |
36 | matches a given message digest B<dgst> of size B<len>. | |
37 | B<dsa> is the signer's public key. | |
38 | ||
39 | The B<type> parameter is ignored. | |
40 | ||
74235cc9 UM |
41 | The PRNG must be seeded before DSA_sign() (or DSA_sign_setup()) |
42 | is called. | |
43 | ||
38e33cef UM |
44 | =head1 RETURN VALUES |
45 | ||
46 | DSA_sign() and DSA_sign_setup() return 1 on success, 0 on error. | |
47 | DSA_verify() returns 1 for a valid signature, 0 for an incorrect | |
48 | signature and -1 on error. The error codes can be obtained by | |
9b86974e | 49 | L<ERR_get_error(3)>. |
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50 | |
51 | =head1 CONFORMING TO | |
52 | ||
53 | US Federal Information Processing Standard FIPS 186 (Digital Signature | |
54 | Standard, DSS), ANSI X9.30 | |
55 | ||
56 | =head1 SEE ALSO | |
57 | ||
9b86974e RS |
58 | L<dsa(3)>, L<ERR_get_error(3)>, L<rand(3)>, |
59 | L<DSA_do_sign(3)> | |
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60 | |
61 | =head1 HISTORY | |
62 | ||
63 | DSA_sign() and DSA_verify() are available in all versions of SSLeay. | |
64 | DSA_sign_setup() was added in SSLeay 0.8. | |
65 | ||
66 | =cut |