Funny Fractal Encryption

/* Mandelbrot Set ASCII by Chris M. Thomasson   :^)
___________________________________________________________________*/


#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>


#define CT_MIN(mp_0, mp_1) (((mp_0) < (mp_1)) ? (mp_0) : (mp_1))
#define CT_SQ(mp_n) ((mp_n) * (mp_n))


#define CT_MBROT_ABET_PUNC \
    " ,./\\;'[]-=<>?:""{}_+`~"

#define CT_MBROT_ABET_NUM_SHIFT \
    "!@#$%^&*()"

#define CT_MBROT_ABET_NUM \
    "0123456789"

#define CT_MBROT_ABET_UPPER \
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

#define CT_MBROT_ABET_LOWER \
    "abcdefghijklmnopqrstuvwxyz"


#define CT_MBROT_ABET       \
    CT_MBROT_ABET_UPPER     \
    CT_MBROT_ABET_LOWER     \
    CT_MBROT_ABET_NUM       \
    CT_MBROT_ABET_NUM_SHIFT \
    CT_MBROT_ABET_PUNC

#define CT_MBROT_ABET_MOD (sizeof(CT_MBROT_ABET) - 1U)

#define CT_MBROT_ABET_LOOKUP(mp_char) \
    ((strchr(CT_MBROT_ABET, (mp_char))) - CT_MBROT_ABET)


struct ct_mbrotcp_pixel
{
    double x;
    double y;
};


struct ct_mbrotcp_plane
{
    double xmin;
    double xmax;
    double ymin;
    double ymax;
};


struct ct_mbrotvp_plane
{
    unsigned int width;
    unsigned int height;
};




unsigned int
ct_mbrotpixel(
    struct ct_mbrotcp_pixel const* pixel_c,
    unsigned int const imax
){
    unsigned int i = 0;
    unsigned int ret = 0;

    struct ct_mbrotcp_pixel pixel_z = *pixel_c;

    struct ct_mbrotcp_pixel pixel_z_sq = {
        CT_SQ(pixel_z.x), CT_SQ(pixel_z.y)
    };

    struct ct_mbrotcp_pixel pixel_cj = { -0.7, 0.0 };

    double cmin = 9999999999999.0;

    for (i = 0; i < imax; ++i)
    {
        pixel_z.y = pixel_z.x * pixel_z.y * 2.0 + pixel_cj.y;
        pixel_z.x = pixel_z_sq.x - pixel_z_sq.y + pixel_cj.x;

        pixel_z_sq.x = CT_SQ(pixel_z.x);
        pixel_z_sq.y = CT_SQ(pixel_z.y);

        cmin = CT_MIN(cmin, CT_SQ(pixel_z_sq.x) + CT_SQ(pixel_z_sq.y));

        if (pixel_z_sq.x + pixel_z_sq.y > 2357)
        {
            ret = (unsigned int)(113747 * fabs(cos(i * cmin * 573)));

            putchar(CT_MBROT_ABET[ret % CT_MBROT_ABET_MOD]);

            return ret;
        }
    }

    {
        unsigned int mc = 0;

        ret = (unsigned int)(234777 * fabs(sin(i * cmin * 3233)));
        mc = ret % CT_MBROT_ABET_MOD;

        putchar(CT_MBROT_ABET[mc]);

        /* uncomment to display points that escape as "blanks" */
        /* putchar(' '); */
    }

    return ret;
}


void
ct_mbrotplane(
    struct ct_mbrotcp_plane const* cp_plane,
    struct ct_mbrotvp_plane const* vp_plane,
    unsigned int const imax,
    unsigned int* icounts
){
    unsigned int vpyi = 0;

    struct ct_mbrotcp_pixel cp_pixel = { 0.0, 0.0 };

    double const cp_width = cp_plane->xmax - cp_plane->xmin;
    double const cp_height = cp_plane->ymax - cp_plane->ymin;

    double const xstep = cp_width / vp_plane->width;
    double const ystep = cp_height / vp_plane->height;

    for (vpyi = 0; vpyi < vp_plane->height; ++vpyi)
    {
        unsigned int vpxi = 0;

        cp_pixel.y = cp_plane->ymax - vpyi * ystep;

        for (vpxi = 0; vpxi < vp_plane->width; ++vpxi)
        {
            cp_pixel.x = cp_plane->xmin + vpxi * xstep;

            unsigned int icount = ct_mbrotpixel(&cp_pixel, imax);

            if (icounts)
            {
                unsigned int i = (vpyi * vp_plane->width) + vpxi;

                icounts[i] = icount;
            }
        }

        putchar('\n');
    }
}







/* Funny Fractal Encryption
___________________________________________________________________*/

#define CT_FFE_ABET_NUM     CT_MBROT_ABET_PUNC
#define CT_FFE_ABET_UPPER   CT_MBROT_ABET_UPPER
#define CT_FFE_ABET_LOWER   CT_MBROT_ABET_LOWER
#define CT_FFE_ABET         CT_MBROT_ABET
#define CT_FFE_ABET_MOD     CT_MBROT_ABET_MOD
#define CT_FFE_ABET_LOOKUP  CT_MBROT_ABET_LOOKUP



struct ct_ffe
{
    struct ct_mbrotcp_plane cp_plane;
    struct ct_mbrotvp_plane vp_plane;
    unsigned int* icounts;
};



int
ct_ffe_create(
    struct ct_ffe* const self
){
    unsigned int n = self->vp_plane.width * self->vp_plane.height;

    self->icounts = calloc(n, sizeof(*self->icounts));

    if (self->icounts)
    {
        return 1;
    }

    return 0;
}


void
ct_ffe_destroy(
    struct ct_ffe* const self
){
    free(self->icounts);
}


void
ct_ffe_encrypt_prepare(
    struct ct_ffe* const self,
    unsigned int const imax
){
    ct_mbrotplane(&self->cp_plane, &self->vp_plane, imax, self->icounts);
}


int
ct_ffe_encrypt(
    struct ct_ffe* const self,
    char const* omsg,
    unsigned int omsg_size,
    char* emsg,
    unsigned int emsg_size
){
    unsigned int i = 0;

    if (emsg_size < omsg_size)
    {
        return 0;
    }

    for (i = 0; i < omsg_size; ++i)
    {
        unsigned int icount = self->icounts[i] % CT_FFE_ABET_MOD;
        unsigned int cx = CT_FFE_ABET_LOOKUP(omsg[i]);
        unsigned int ec = (cx + icount) % CT_FFE_ABET_MOD;

        emsg[i] = CT_FFE_ABET[ec];
    }

    return 1;
}


int
ct_ffe_decrypt(
    struct ct_ffe* const self,
    char const* emsg,
    unsigned int emsg_size,
    char* dmsg,
    unsigned int dmsg_size
){
    unsigned int i = 0;

    if (dmsg_size < emsg_size)
    {
        return 0;
    }

    for (i = 0; i < emsg_size; ++i)
    {
        unsigned int icount = self->icounts[i] % CT_FFE_ABET_MOD;
        unsigned int cx = CT_FFE_ABET_LOOKUP(emsg[i]);

        int ec = cx - icount;

        if (ec < 0)
        {
            ec = cx + CT_FFE_ABET_MOD;
            ec = abs(icount - ec);
        }

        dmsg[i] = CT_FFE_ABET[ec];
    }

    return 1;
}







/* Sample FFE Usage Program
___________________________________________________________________*/
int
main(void)
{
    char omsg[] = "/Fun\\ <with> [Fractals]! (tm) `Hello'";
    char emsg[sizeof(omsg)] = { '\0' };
    char dmsg[sizeof(omsg)] = { '\0' };

    unsigned int n = sizeof(omsg) - 1;
    unsigned int dim = (((unsigned int)sqrt(n)) + 1);
    unsigned int dim_scale = 3;
    unsigned int gwidth = dim * dim_scale;
    unsigned int gheight = gwidth;


    struct ct_ffe fe = {
        { -1.1, 1.0, -1.0, 1.413 },
        { gwidth, gheight },
        NULL
    };

    if (ct_ffe_create(&fe))
    {
        printf(
            "CT_FFE_ABET_MOD = %u\r\n"
            "________________________________\r\n"
            "Fractal Pad: z^2 + c (Julia Set)\r\n"
            "Grid Dims:   %u x %u\r\n"
            "--------------------------------\r\n",
            (unsigned int)CT_FFE_ABET_MOD,
            gwidth,
            gheight
        );

        ct_ffe_encrypt_prepare(&fe, CT_FFE_ABET_MOD * dim_scale);

        printf("________________________________\r\n");

        if (ct_ffe_encrypt(&fe, omsg, n, emsg, n))
        {
            if (ct_ffe_decrypt(&fe, emsg, n, dmsg, n))
            {
                printf("\r\noriginal  = %s\r\n\r\n", omsg);
                printf("encrypted = %s\r\n\r\n", emsg);
                printf("decrypted = %s\r\n", dmsg);
            }
        }

        ct_ffe_destroy(&fe);
    }

    return 0;
}