ed448goldilocks/test/test_pointops.c

#include "test.h"

#include <stdio.h>

#include "ec_point.h"
#include "magic.h"
#include "field.h"
#include "crandom.h"


static void
failprint_ext (
    const struct extensible_t *a
) {
    field_a_t zi, scaled;
    field_print("    x", a->x);
    field_print("    y", a->y);
    field_print("    z", a->z);
    field_inverse(zi, a->z);
    field_mul(scaled, zi, a->x);
    field_print("    X", scaled);
    field_mul(scaled, zi, a->y);
    field_print("    Y", scaled);
    printf("\n");
}

static void
failprint_tw_ext (
    const struct tw_extensible_t *a
) {
    failprint_ext((const struct extensible_t *)a);
}

static mask_t
fail_if_different (
    const struct extensible_t *a,
    const struct extensible_t *b,
    const char *faildescr,
    const char *adescr,
    const char *bdescr
) {
    mask_t succ = eq_extensible(a, b);
    
    if (!succ) {
        youfail();
        printf("    %s\n", faildescr);
        
        printf("\n    %s:\n", adescr);
        failprint_ext(a);
        
        printf("\n    %s:\n", bdescr);
        failprint_ext(b);
    }
    
    return succ;
}

static mask_t
validate_ext(
    const struct extensible_t *ext,
    int evenness,
    const char *description
) {
    mask_t succ = validate_extensible(ext), succ2;
    const char *error = "Point isn't on the curve.";
    if (evenness > 0) {
        succ2 = is_even_pt(ext);
        if (succ &~ succ2) error = "Point isn't even.";
        succ &= succ2;
    } else if (evenness < 0) {
        succ2 = is_even_pt(ext);
        if (succ &~ succ2) error = "Point is even but shouldn't be.";
        succ &= succ2;
    } /* FUTURE: quadness */
    
    if (~succ) {
        youfail();
        printf("    %s\n", error);
        printf("    %s\n", description);
        failprint_ext(ext);
    }
    
    return succ;
}

static mask_t
validate_tw_ext(
    const struct tw_extensible_t *ext,
    int evenness,
    const char *description
) {
    mask_t succ = validate_tw_extensible(ext), succ2;
    const char *error = "Point isn't on the twisted curve.";
    if (evenness > 0) {
        succ2 = is_even_tw(ext);
        if (succ &~ succ2) error = "Point isn't even.";
        succ &= succ2;
    } else if (evenness < 0) {
        succ2 = is_even_tw(ext);
        if (succ &~ succ2) error = "Point is even but shouldn't be.";
        succ &= succ2;
    } /* FUTURE: quadness */
    
    if (~succ) {
        youfail();
        printf("    %s\n", error);
        printf("    %s\n", description);
        failprint_tw_ext(ext);
    }
    
    return succ;
}

static mask_t
fail_if_different_tw (
    const struct tw_extensible_t *a,
    const struct tw_extensible_t *b,
    const char *faildescr,
    const char *adescr,
    const char *bdescr
) {
    return fail_if_different(
        (const struct extensible_t *)a, (const struct extensible_t *)b,
        faildescr,adescr,bdescr
    );
}

static int
add_double_test (
    const struct affine_t *base1,
    const struct affine_t *base2 
) {
    mask_t succ = MASK_SUCCESS;
    struct extensible_t exb;
    struct tw_extensible_t text1, text2, texta, textb;
    struct tw_pniels_t pn;
    
    /* Convert to ext */
    convert_affine_to_extensible(&exb, base1);
    succ &= validate_ext(&exb,0,"base1");
    twist_and_double(&text1, &exb);
    succ &= validate_tw_ext(&text1,2,"iso1");
    convert_affine_to_extensible(&exb, base2);
    succ &= validate_ext(&exb,0,"base2");
    twist_and_double(&text2, &exb);
    succ &= validate_tw_ext(&text2,2,"iso2");
    
    /* a + b == b + a? */
    convert_tw_extensible_to_tw_pniels(&pn, &text1);
    copy_tw_extensible(&texta, &text2);
    add_tw_pniels_to_tw_extensible(&texta, &pn);
    
    convert_tw_extensible_to_tw_pniels(&pn, &text2);
    copy_tw_extensible(&textb, &text1);
    add_tw_pniels_to_tw_extensible(&textb, &pn);
    
    succ &= fail_if_different_tw(&texta,&textb,"Addition commutativity","a+b","b+a");
    
    copy_tw_extensible(&textb, &text2);
    add_tw_pniels_to_tw_extensible(&textb, &pn);
    copy_tw_extensible(&texta, &text2);
    double_tw_extensible(&texta);
    
    succ &= fail_if_different_tw(&texta,&textb,"Doubling test","2b","b+b");
    
    if (~succ) {
        printf("    Bases were:\n");
        field_print("    x1", base1->x);
        field_print("    y1", base1->y);
        field_print("    x2", base2->x);
        field_print("    y2", base2->y);
    }
    
    return succ ? 0 : -1;
}

static int
single_twisting_test (
    const struct affine_t *base
) {
    struct extensible_t exb, ext, tmpext;
    struct tw_extensible_t text, text2;
    mask_t succ = MASK_SUCCESS;
    
    convert_affine_to_extensible(&exb, base);
    succ &= validate_ext(&exb,0,"base");
    
    /* check: dual . iso = 4 */
    twist_and_double(&text, &exb);
    succ &= validate_tw_ext(&text,2,"iso");
    untwist_and_double(&ext, &text);
    succ &= validate_ext(&ext,2,"dual.iso");
    
    copy_extensible(&tmpext,&exb);
    double_extensible(&tmpext);
    succ &= validate_ext(&tmpext,1,"2*base");
    
    double_extensible(&tmpext);
    succ &= validate_ext(&tmpext,2,"4*base");
    
    succ &= fail_if_different(&ext,&tmpext,"Isogeny and dual","Dual . iso","4*base");
    
    /* check: twist and serialize */
    test_only_twist(&text, &exb);
    succ &= validate_tw_ext(&text,0,"tot");
    mask_t evt = is_even_tw(&text), evb = is_even_pt(&exb);
    if (evt != evb) {
        youfail();
        printf("    Different evenness from twist base: %d, twist: %d\n", (int)-evt, (int)-evb);
        
        succ = 0;
    } /* FUTURE: quadness */
    
    field_a_t sera,serb;
    untwist_and_double_and_serialize(sera,&text);
    copy_extensible(&tmpext,&exb);
    double_extensible(&tmpext);
    serialize_extensible(serb,&tmpext);
    
    /* check that their (doubled; FUTURE?) serializations are equal */
    if (~field_eq(sera,serb)) {
        youfail();
        printf("    Different serialization from twist + double ()\n");
        field_print("    t", sera);
        field_print("    b", serb);
        succ = 0;
    }
    
    untwist_and_double(&ext, &text);
    succ &= validate_ext(&tmpext,1,"dual.tot");
    
    twist_and_double(&text2, &ext);
    succ &= validate_tw_ext(&text2,2,"iso.dual.tot");

    double_tw_extensible(&text);
    succ &= validate_tw_ext(&text,1,"2*tot");

    double_tw_extensible(&text);
    succ &= validate_tw_ext(&text,2,"4*tot");
    
    succ &= fail_if_different_tw(&text,&text2,"Dual and isogeny","4*tot","iso.dual.tot");
    
    if (~succ) {
        printf("    Base was:\n");
        field_print("    x", base->x);
        field_print("    y", base->y);
    }
    
    
    return succ ? 0 : -1;
}

int test_pointops (void) {
    struct affine_t base, pbase;
    field_a_t serf;
    
    struct crandom_state_t crand;
    crandom_init_from_buffer(&crand, "test_pointops random initializer");
    
    struct extensible_t ext_base;
    if (!validate_affine(goldilocks_base_point)) {
        youfail();
        printf("  Base point isn't on the curve.\n");
        return -1;
    }
    convert_affine_to_extensible(&ext_base, goldilocks_base_point);
    if (!validate_ext(&ext_base, 2, "base")) return -1;
    
    int i, ret;
    for (i=0; i<1000; i++) {
        uint8_t ser[FIELD_BYTES];
        crandom_generate(&crand, ser, sizeof(ser));


        #if (FIELD_BITS % 8)
            ser[FIELD_BYTES-1] &= (1<<(FIELD_BITS%8)) - 1;
        #endif
        
        /* TODO: we need a field generate, which can return random or pathological. */
        mask_t succ = field_deserialize(serf, ser);
        if (!succ) {
            youfail();
            printf("   Unlikely: fail at field_deserialize\n");
            return -1;
        }
        
        if (i) {
            copy_affine(&pbase, &base);
        }
        elligator_2s_inject(&base, serf);
        
        if (i) {
            ret = add_double_test(&base, &pbase);
            if (ret) return ret;
        }
        
        ret = single_twisting_test(&base);
        if (ret) return ret;
    }
    
    return 0;
}