X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/70f31709e822f1a1877cf72d7f27bab5259b6c9d..41a324a748544b0fb9b0acfc65b1a39b7611550c:/ec.c diff --git a/ec.c b/ec.c index 604190b..37d8ad3 100644 --- a/ec.c +++ b/ec.c @@ -1,6 +1,6 @@ /* -*-c-*- * - * $Id: ec.c,v 1.1 2001/04/29 18:12:33 mdw Exp $ + * $Id: ec.c,v 1.2 2001/05/07 17:29:44 mdw Exp $ * * Elliptic curve definitions * @@ -30,6 +30,10 @@ /*----- Revision history --------------------------------------------------* * * $Log: ec.c,v $ + * Revision 1.2 2001/05/07 17:29:44 mdw + * Treat projective coordinates as an internal representation. Various + * minor interface changes. + * * Revision 1.1 2001/04/29 18:12:33 mdw * Prototype version. * @@ -97,21 +101,22 @@ void ec_setinf(ec *p) { EC_SETINF(p); } void ec_copy(ec *d, const ec *p) { EC_COPY(d, p); } -/*----- Real arithmetic ---------------------------------------------------*/ +/*----- Standard curve operations -----------------------------------------*/ -/* --- @ec_denorm@ --- * +/* --- @ec_idin@, @ec_idout@ --- * * * Arguments: @ec_curve *c@ = pointer to an elliptic curve - * @ec *d@ = pointer to the destination point - * @const ec *p@ = pointer to the source point + * @ec *d@ = pointer to the destination + * @const ec *p@ = pointer to a source point * - * Returns: --- + * Returns: The destination @d@. * - * Use: Denormalizes the given point, converting to internal - * representations and setting the denominator to 1. + * Use: An identity operation if your curve has no internal + * representation. (The field internal representation is still + * used.) */ -void ec_denorm(ec_curve *c, ec *d, const ec *p) +ec *ec_idin(ec_curve *c, ec *d, const ec *p) { if (EC_ATINF(p)) EC_SETINF(d); @@ -119,24 +124,50 @@ void ec_denorm(ec_curve *c, ec *d, const ec *p) field *f = c->f; d->x = F_IN(f, d->x, p->x); d->y = F_IN(f, d->y, p->y); - mp_drop(d->z); - d->z = MP_COPY(f->one); + mp_drop(d->z); d->z = 0; + } + return (d); +} + +ec *ec_idout(ec_curve *c, ec *d, const ec *p) +{ + if (EC_ATINF(p)) + EC_SETINF(d); + else { + field *f = c->f; + d->x = F_OUT(f, d->x, p->x); + d->y = F_OUT(f, d->y, p->y); + mp_drop(d->z); d->z = 0; } + return (d); } -/* --- @ec_norm@ --- * +/* --- @ec_projin@, @ec_projout@ --- * * * Arguments: @ec_curve *c@ = pointer to an elliptic curve - * @ec *d@ = pointer to the destination point - * @const ec *p@ = pointer to the source point + * @ec *d@ = pointer to the destination + * @const ec *p@ = pointer to a source point * - * Returns: --- + * Returns: The destination @d@. * - * Use: Normalizes the given point, by dividing through by the - * denominator and returning to external representation. + * Use: Conversion functions if your curve operations use a + * projective representation. */ -void ec_norm(ec_curve *c, ec *d, const ec *p) +ec *ec_projin(ec_curve *c, ec *d, const ec *p) +{ + if (EC_ATINF(p)) + EC_SETINF(d); + else { + field *f = c->f; + d->x = F_IN(f, d->x, p->x); + d->y = F_IN(f, d->y, p->y); + mp_drop(d->z); d->z = MP_COPY(f->one); + } + return (d); +} + +ec *ec_projout(ec_curve *c, ec *d, const ec *p) { if (EC_ATINF(p)) EC_SETINF(d); @@ -152,8 +183,11 @@ void ec_norm(ec_curve *c, ec *d, const ec *p) d->y = F_OUT(f, y, y); d->z = 0; } + return (d); } +/*----- Real arithmetic ---------------------------------------------------*/ + /* --- @ec_find@ --- * * * Arguments: @ec_curve *c@ = pointer to an elliptic curve @@ -165,14 +199,13 @@ void ec_norm(ec_curve *c, ec *d, const ec *p) * Use: Finds a point on an elliptic curve with a given x-coordinate. */ -void ec_find(ec_curve *c, ec *d, mp *x) +ec *ec_find(ec_curve *c, ec *d, mp *x) { - int rc; x = F_IN(c->f, MP_NEW, x); - if ((rc = EC_FIND(c, d, x)) == 0) - ec_norm(c, d, d); + if ((d = EC_FIND(c, d, x)) != 0) + EC_OUT(c, d, d); mp_drop(x); - return (rc); + return (d); } /* --- @ec_add@ --- * @@ -186,15 +219,16 @@ void ec_find(ec_curve *c, ec *d, mp *x) * Use: Adds two points on an elliptic curve. */ -void ec_add(ec_curve *c, ec *d, const ec *p, const ec *q) +ec *ec_add(ec_curve *c, ec *d, const ec *p, const ec *q) { ec pp = EC_INIT, qq = EC_INIT; - ec_denorm(c, &pp, p); - ec_denorm(c, &qq, q); + EC_IN(c, &pp, p); + EC_IN(c, &qq, q); EC_ADD(c, d, &pp, &qq); - ec_norm(c, d, d); + EC_OUT(c, d, d); EC_DESTROY(&pp); EC_DESTROY(&qq); + return (d); } /* --- @ec_dbl@ --- * @@ -208,11 +242,11 @@ void ec_add(ec_curve *c, ec *d, const ec *p, const ec *q) * Use: Doubles a point on an elliptic curve. */ -void ec_dbl(ec_curve *c, ec *d, const ec *p) +ec *ec_dbl(ec_curve *c, ec *d, const ec *p) { - ec_denorm(c, d, p); + EC_IN(c, d, p); EC_DBL(c, d, d); - ec_norm(c, d, d); + return (EC_OUT(c, d, d)); } /* --- @ec_mul@ --- * @@ -227,7 +261,7 @@ void ec_dbl(ec_curve *c, ec *d, const ec *p) * Use: Multiplies a point by a scalar, returning %$n p$%. */ -void ec_mul(ec_curve *c, ec *d, const ec *p, mp *n) +ec *ec_mul(ec_curve *c, ec *d, const ec *p, mp *n) { mpscan sc; ec g = EC_INIT; @@ -243,7 +277,7 @@ void ec_mul(ec_curve *c, ec *d, const ec *p, mp *n) while (!MP_RBIT(&sc)) MP_RSTEP(&sc); - ec_denorm(c, &g, p); + EC_IN(c, &g, p); if ((n->f & MP_BURN) && !(g.x->f & MP_BURN)) MP_DEST(g.x, 0, MP_BURN); if ((n->f & MP_BURN) && !(g.y->f & MP_BURN)) @@ -274,7 +308,7 @@ done: EC_DESTROY(&g); exit: - ec_norm(c, d, d); + return (EC_OUT(c, d, d)); } /*----- That's all, folks -------------------------------------------------*/