DSA(2) DSA(2) NAME dsagen, dsasign, dsaverify, dsapuballoc, dsapubfree, dsaprivalloc, dsaprivfree, dsasigalloc, dsasigfree, dsaprivtopub - digital signature algorithm SYNOPSIS #include <u.h> #include <libc.h> #include <mp.h> #include <libsec.h> DSApriv* dsagen(DSApub *opub) DSAsig* dsasign(DSApriv *k, mpint *m) int dsaverify(DSApub *k, DSAsig *sig, mpint *m) DSApub* dsapuballoc(void) void dsapubfree(DSApub*) DSApriv* dsaprivalloc(void) void dsaprivfree(DSApriv*) DSAsig* dsasigalloc(void) void dsasigfree(DSAsig*) DSApub* dsaprivtopub(DSApriv*) DESCRIPTION DSA is the NIST approved digital signature algorithm. The owner of a key publishes the public part of the key: struct DSApub { mpint *p; // modulus mpint *q; // group order, q divides p-1 mpint *alpha; // group generator mpint *key; // alpha**secret mod p }; This part can be used for verifying signatures (with dsaverify) created by the owner. The owner signs (with dsasign) using his private key: struct DSApriv { DSApub pub; Page 1 Plan 9 (printed 12/4/24) DSA(2) DSA(2) mpint *secret; // (decryption key) }; Keys are generated using dsagen. If dsagen's argument opub is nil, a key is created using a new p and q generated by DSAprimes (see prime(2)). Otherwise, p and q are copied from the old key. Dsaprivtopub returns a newly allocated copy of the public key corresponding to the private key. The routines dsapuballoc, dsapubfree, dsaprivalloc, and dsaprivfree are provided to manage key storage. Dsasign signs message m using a private key k yielding a struct DSAsig { mpint *r, *s; }; Dsaverify returns 0 if the signature is valid and -1 if not. The routines dsasigalloc and dsasigfree are provided to man- age signature storage. SOURCE /sys/src/libsec SEE ALSO mp(2), aes(2), blowfish(2), des(2), rc4(2), rsa(2), sechash(2), prime(2), rand(2) Page 2 Plan 9 (printed 12/4/24)