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)

intdsaverify(DSApub ∗k, DSAsig ∗sig, mpint ∗m)

DSApub∗dsapuballoc(void)

voiddsapubfree(DSApub∗)

DSApriv∗dsaprivalloc(void)

voiddsaprivfree(DSApriv∗)

DSAsig∗dsasigalloc(void)

voiddsasigfree(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
{
DSApubpub;
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(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 manage 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)

Plan 9  —  July 25, 2002