dsa(3)

NAME
dsa - Digital Signature Algorithm

SYNOPSIS
 #include <openssl/dsa.h>

 DSA *  DSA_new(void);
 void   DSA_free(DSA *dsa);

 int    DSA_size(DSA *dsa);

 DSA *  DSA_generate_parameters(int bits, unsigned char *seed,
                int seed_len, int *counter_ret, unsigned long *h_ret,
                void (*callback)(int, int, void *), void *cb_arg);

 DH *   DSA_dup_DH(DSA *r);

 int    DSA_generate_key(DSA *dsa);

 int    DSA_sign(int dummy, const unsigned char *dgst, int len,
                unsigned char *sigret, unsigned int *siglen, DSA *dsa);
 int    DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp,
                BIGNUM **rp);
 int    DSA_verify(int dummy, const unsigned char *dgst, int len,
                unsigned char *sigbuf, int siglen, DSA *dsa);

 void DSA_set_default_method(DSA_METHOD *meth);
 DSA_METHOD *DSA_get_default_method(void);
 DSA_METHOD *DSA_set_method(DSA *dsa, DSA_METHOD *meth);
 DSA *DSA_new_method(DSA_METHOD *meth);
 DSA_METHOD *DSA_OpenSSL(void);

 int DSA_get_ex_new_index(long argl, char *argp, int (*new_func)(),
             int (*dup_func)(), void (*free_func)());
 int DSA_set_ex_data(DSA *d, int idx, char *arg);
 char *DSA_get_ex_data(DSA *d, int idx);

 DSA_SIG *DSA_SIG_new(void);
 void   DSA_SIG_free(DSA_SIG *a);
 int    i2d_DSA_SIG(DSA_SIG *a, unsigned char **pp);
 DSA_SIG *d2i_DSA_SIG(DSA_SIG **v, unsigned char **pp, long length);

 DSA_SIG *DSA_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
 int    DSA_do_verify(const unsigned char *dgst, int dgst_len,
             DSA_SIG *sig, DSA *dsa);

 DSA *  d2i_DSAPublicKey(DSA **a, unsigned char **pp, long length);
 DSA *  d2i_DSAPrivateKey(DSA **a, unsigned char **pp, long length);
 DSA *  d2i_DSAparams(DSA **a, unsigned char **pp, long length);
 int    i2d_DSAPublicKey(DSA *a, unsigned char **pp);
 int    i2d_DSAPrivateKey(DSA *a, unsigned char **pp);
 int    i2d_DSAparams(DSA *a,unsigned char **pp);

 int    DSAparams_print(BIO *bp, DSA *x);
 int    DSAparams_print_fp(FILE *fp, DSA *x);
 int    DSA_print(BIO *bp, DSA *x, int off);
 int    DSA_print_fp(FILE *bp, DSA *x, int off);

DESCRIPTION
These functions implement the Digital Signature Algorithm (DSA). The generation of shared DSA parameters is described in DSA_generate_parameters(3); DSA_generate_key(3) describes how to generate a signature key. Signature generation and verification are described in DSA_sign(3).

The DSA structure consists of several BIGNUM components.

 struct
        {
        BIGNUM *p;              // prime number (public)
        BIGNUM *q;              // 160-bit subprime, q | p-1 (public)
        BIGNUM *g;              // generator of subgroup (public)
        BIGNUM *priv_key;       // private key x
        BIGNUM *pub_key;        // public key y = g^x
        // ...
        }
 DSA;

In public keys, priv_key is NULL.

CONFORMING TO
US Federal Information Processing Standard FIPS 186 (Digital Signature Standard, DSS), ANSI X9.30

SEE ALSO
bn(3), dh(3), err(3), rand(3), rsa(3), sha(3), DSA_new(3), DSA_size(3), DSA_generate_parameters(3), DSA_dup_DH(3), DSA_generate_key(3), DSA_sign(3), DSA_set_method(3), DSA_get_ex_new_index(3), RSA_print(3)