Форум программистов [Powered by Invision Power Board]

Код

#include <stdlib.h>
#include <stdio.h>
#include <time.h>

long P=1003;
long a=357;
long g=2;
long b;

long g_in_a(long g,long a,long P);
void shifruem();
void rasshifruem();
void ax_by_c(long A, long *X, long B, long *Y, long C);

int main()
{
    b = g_in_a(g,a,P);
    shifruem();
    rasshifruem();
    return 0;
}

void shifruem()
{
    FILE *fi,*fo;
    fi = fopen("in.txt","r");
    fo = fopen("out.txt","w");
    char c;
    long r=7;
    long C1, C2;
    long X=0;
    srand( (unsigned)time( NULL ) );
    while( fscanf(fi,"%c",&c)!=EOF )
    {
        if( c>='A' && c<='Z' ) c=c-'A'+'a';
        if( c>='a' && c<='z' )
        {
            r = (long)((double)rand()/(double)RAND_MAX*(P-2)+1);
            c -= 'a'; c += 10;
            X = c;
            C1 = g_in_a(g,r,P);
            C2 = g_in_a(b,r,P);
            C2 = (C2*X)%P;
            fprintf(fo,"%d %d  ",C1,C2);
        }
    }
    fclose(fo);
    fclose(fi);
}

void rasshifruem()
{
    FILE *fi,*fo;
    fi = fopen("out.txt","r");
    fo = fopen("out2.txt","w");

    long C1, C2;
    long X=0, t, Y;
    int k=0;
    while( fscanf(fi,"%d%d",&C1, &C2)!=EOF )
    {
        t = g_in_a(C1,a,P);
        ax_by_c( t, &X, P, &Y, C2 );        
        while( X<0 ) X += P;
        X = X%P;
        fprintf(fo,"%c",X-10+'a');
        k++;
        if( k==6 ){ k=0; fprintf(fo," "); }
    }
    fclose(fo);
    fclose(fi);
}


void ax_by_c(long A, long *X, long B, long *Y, long C)
{
    long E[2][2];
    E[0][0]=1; E[0][1]=0;
    E[1][1]=1; E[1][0]=0;
    long e1,e2,e3,e4;
    long k, r;
    while(1)
    {
        r=A%B;
        if( r==0 ) break;
        k=(A-r)/B;
        e1=E[0][1]; e2=E[0][0]-E[0][1]*k;
        e3=E[1][1]; e4=E[1][0]-E[1][1]*k;
        E[0][0]=e1; E[0][1]=e2;
        E[1][0]=e3; E[1][1]=e4;
        A=B; B=r;
    }
    (*Y)=E[1][1]*C;
    (*X)= E[0][1]*C;
}

long g_in_a(long g,long a,long P)
{
    long r;
    int d[30], n=0, i;
    
    while( a>0 )
    {
           d[n++]=a%2;
           a/=2;
    }
    for( r=g, i=n-2; i>=0; --i )
    {
        r=(r*r)%P;
        if( d[i]==1 ) r=(r*g)%P;
    }
    return r;         
}