=pod
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=head1 NAME
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dsa - Digital Signature Algorithm
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=head1 SYNOPSIS
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#include <openssl/dsa.h>
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#include <openssl/engine.h>
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DSA * DSA_new(void);
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void DSA_free(DSA *dsa);
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int DSA_size(const DSA *dsa);
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DSA * DSA_generate_parameters(int bits, unsigned char *seed,
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int seed_len, int *counter_ret, unsigned long *h_ret,
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void (*callback)(int, int, void *), void *cb_arg);
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DH * DSA_dup_DH(const DSA *r);
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int DSA_generate_key(DSA *dsa);
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int DSA_sign(int dummy, const unsigned char *dgst, int len,
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unsigned char *sigret, unsigned int *siglen, DSA *dsa);
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int DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp,
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BIGNUM **rp);
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int DSA_verify(int dummy, const unsigned char *dgst, int len,
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const unsigned char *sigbuf, int siglen, DSA *dsa);
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void DSA_set_default_method(const DSA_METHOD *meth);
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const DSA_METHOD *DSA_get_default_method(void);
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int DSA_set_method(DSA *dsa, const DSA_METHOD *meth);
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DSA *DSA_new_method(ENGINE *engine);
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const DSA_METHOD *DSA_OpenSSL(void);
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int DSA_get_ex_new_index(long argl, char *argp, int (*new_func)(),
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int (*dup_func)(), void (*free_func)());
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int DSA_set_ex_data(DSA *d, int idx, char *arg);
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char *DSA_get_ex_data(DSA *d, int idx);
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DSA_SIG *DSA_SIG_new(void);
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void DSA_SIG_free(DSA_SIG *a);
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int i2d_DSA_SIG(const DSA_SIG *a, unsigned char **pp);
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DSA_SIG *d2i_DSA_SIG(DSA_SIG **v, unsigned char **pp, long length);
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DSA_SIG *DSA_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
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int DSA_do_verify(const unsigned char *dgst, int dgst_len,
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DSA_SIG *sig, DSA *dsa);
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DSA * d2i_DSAPublicKey(DSA **a, unsigned char **pp, long length);
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DSA * d2i_DSAPrivateKey(DSA **a, unsigned char **pp, long length);
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DSA * d2i_DSAparams(DSA **a, unsigned char **pp, long length);
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int i2d_DSAPublicKey(const DSA *a, unsigned char **pp);
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int i2d_DSAPrivateKey(const DSA *a, unsigned char **pp);
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int i2d_DSAparams(const DSA *a,unsigned char **pp);
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int DSAparams_print(BIO *bp, const DSA *x);
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int DSAparams_print_fp(FILE *fp, const DSA *x);
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int DSA_print(BIO *bp, const DSA *x, int off);
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int DSA_print_fp(FILE *bp, const DSA *x, int off);
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=head1 DESCRIPTION
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These functions implement the Digital Signature Algorithm (DSA). The
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generation of shared DSA parameters is described in
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L<DSA_generate_parameters(3)|DSA_generate_parameters(3)>;
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L<DSA_generate_key(3)|DSA_generate_key(3)> describes how to
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generate a signature key. Signature generation and verification are
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described in L<DSA_sign(3)|DSA_sign(3)>.
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The B<DSA> structure consists of several BIGNUM components.
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struct
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{
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BIGNUM *p; // prime number (public)
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BIGNUM *q; // 160-bit subprime, q | p-1 (public)
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BIGNUM *g; // generator of subgroup (public)
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BIGNUM *priv_key; // private key x
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BIGNUM *pub_key; // public key y = g^x
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// ...
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}
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DSA;
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In public keys, B<priv_key> is NULL.
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Note that DSA keys may use non-standard B<DSA_METHOD> implementations,
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either directly or by the use of B<ENGINE> modules. In some cases (eg. an
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ENGINE providing support for hardware-embedded keys), these BIGNUM values
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will not be used by the implementation or may be used for alternative data
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storage. For this reason, applications should generally avoid using DSA
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structure elements directly and instead use API functions to query or
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modify keys.
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=head1 CONFORMING TO
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US Federal Information Processing Standard FIPS 186 (Digital Signature
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Standard, DSS), ANSI X9.30
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=head1 SEE ALSO
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L<bn(3)|bn(3)>, L<dh(3)|dh(3)>, L<err(3)|err(3)>, L<rand(3)|rand(3)>,
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L<rsa(3)|rsa(3)>, L<sha(3)|sha(3)>, L<engine(3)|engine(3)>,
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L<DSA_new(3)|DSA_new(3)>,
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L<DSA_size(3)|DSA_size(3)>,
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L<DSA_generate_parameters(3)|DSA_generate_parameters(3)>,
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L<DSA_dup_DH(3)|DSA_dup_DH(3)>,
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L<DSA_generate_key(3)|DSA_generate_key(3)>,
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L<DSA_sign(3)|DSA_sign(3)>, L<DSA_set_method(3)|DSA_set_method(3)>,
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L<DSA_get_ex_new_index(3)|DSA_get_ex_new_index(3)>,
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L<RSA_print(3)|RSA_print(3)>
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=cut
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