| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | DSA_sign, DSA_sign_setup, DSA_verify - DSA signatures
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/dsa.h>
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| 10 |
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| 11 | int DSA_sign(int type, const unsigned char *dgst, int len,
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| 12 | unsigned char *sigret, unsigned int *siglen, DSA *dsa);
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| 13 |
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| 14 | int DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp, BIGNUM **rp);
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| 15 |
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| 16 | int DSA_verify(int type, const unsigned char *dgst, int len,
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| 17 | unsigned char *sigbuf, int siglen, DSA *dsa);
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| 18 |
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| 19 | =head1 DESCRIPTION
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| 20 |
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| 21 | DSA_sign() computes a digital signature on the B<len> byte message
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| 22 | digest B<dgst> using the private key B<dsa> and places its ASN.1 DER
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| 23 | encoding at B<sigret>. The length of the signature is places in
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| 24 | *B<siglen>. B<sigret> must point to DSA_size(B<dsa>) bytes of memory.
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| 25 |
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| 26 | DSA_sign_setup() is defined only for backward binary compatibility and
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| 27 | should not be used.
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| 28 | Since OpenSSL 1.1.0 the DSA type is opaque and the output of
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| 29 | DSA_sign_setup() cannot be used anyway: calling this function will only
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| 30 | cause overhead, and does not affect the actual signature
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| 31 | (pre-)computation.
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| 32 |
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| 33 | DSA_verify() verifies that the signature B<sigbuf> of size B<siglen>
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| 34 | matches a given message digest B<dgst> of size B<len>.
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| 35 | B<dsa> is the signer's public key.
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| 36 |
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| 37 | The B<type> parameter is ignored.
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| 38 |
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| 39 | The random generator must be seeded when DSA_sign() (or DSA_sign_setup())
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| 40 | is called.
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| 41 | If the automatic seeding or reseeding of the OpenSSL CSPRNG fails due to
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| 42 | external circumstances (see L<RAND(7)>), the operation will fail.
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| 43 |
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| 44 | =head1 RETURN VALUES
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| 45 |
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| 46 | DSA_sign() and DSA_sign_setup() return 1 on success, 0 on error.
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| 47 | DSA_verify() returns 1 for a valid signature, 0 for an incorrect
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| 48 | signature and -1 on error. The error codes can be obtained by
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| 49 | L<ERR_get_error(3)>.
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| 50 |
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| 51 | =head1 CONFORMING TO
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| 52 |
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| 53 | US Federal Information Processing Standard FIPS 186 (Digital Signature
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| 54 | Standard, DSS), ANSI X9.30
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| 55 |
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| 56 | =head1 SEE ALSO
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| 57 |
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| 58 | L<DSA_new(3)>, L<ERR_get_error(3)>, L<RAND_bytes(3)>,
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| 59 | L<DSA_do_sign(3)>,
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| 60 | L<RAND(7)>
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| 61 |
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| 62 | =head1 COPYRIGHT
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| 63 |
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| 64 | Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.
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| 65 |
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| 66 | Licensed under the OpenSSL license (the "License"). You may not use
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| 67 | this file except in compliance with the License. You can obtain a copy
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| 68 | in the file LICENSE in the source distribution or at
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| 69 | L<https://www.openssl.org/source/license.html>.
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| 70 |
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| 71 | =cut
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