jiami.txt

四种加密解密算法的源代码/*辗转相除法求a,b的最大公因数*/

四种加密解密算法的源代码

#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <malloc.h>
void Shift()          /*移位密码*/
{
        char c[100];
        int length, i=0, key=0;
        clrscr();

        printf("********Shift Cipher********\nPlease input primal sentence: ");
        gets(c);
        length = strlen(c);
        printf("Input the key(0~26): ");
        scanf("%d", &key);
        getchar();

        if(key<0)
        {
            printf("The value of key is error!\nPress any key to return...");
            getch();
            return;
        }
        for(i=0; i<length; i++)
        {
            if(c[i]>96&&c[i]<123)
                c[i] = (c[i]+key-97)%26+65;
            else if(c[i]>64&&c[i]<91)
                c[i] = (c[i]+key-65)%26+65;
        }
        printf("Result is: %s\n", c);
        for(i=0; i<length; i++)
        {
            if(c[i]>64&&c[i]<91)
                c[i] = (c[i]-key-65+26)%26+97;
        }
        printf("\nAfter translated the sentence,we can see the primal sentence as follow:\n%s\n", c);
        printf("Press any key to return...");
        getch();
}

int gcd(int a, int b)    /*辗转相除法求a,b的最大公因数*/
{
        int k = 0;

        do
        {
            k = a%b;
            a = b;
            b = k;
        }while(k!=0);
        return a;
}

int Ni(int a, int b)  /*求a相对于b的逆*/
{
        int i = 0;
        while(a*(++i)%b!=1);
        return i;
}

void Affine()          /*仿射密码*/
{
        char c[100];
        int length, i=0, ka=0, kb=0, tmp;
        clrscr();

        printf("********Affine Cipher********\nPlease input primal sentence: ");
        gets(c);
        length = strlen(c);
        printf("Input the key(2 numbers): ");
        scanf("%d%d", &ka, &kb);
        getchar();
        if(gcd(ka,26)!=1)
        {
            printf("The value of the key is error!\nPress any key to return...");
            return;
        }

        for(i=0; i<length; i++)
        {
            if(c[i]>96&&c[i]<123)
                c[i] = (ka*(c[i]-97)+kb)%26+65;
            else if(c[i]>64&&c[i]<91)
                c[i] = (ka*(c[i]-65)+kb)%26+65;
        }
        printf("Result is: %s\n", c);
        for(i=0; i<length; i++)
        {
            if(c[i]>64&&c[i]<91)
            {
                tmp = Ni(ka,26)*((c[i]-65)-kb);
                if(tmp<0)
                    c[i] = tmp%26+26+97;
                else
                    c[i] = tmp%26+97;
            }
        }
        printf("\nAfter translated the sentence,we can see the primal sentence as follow:\n%s\n", c);
        printf("Press any key to return...");
        getch();
}

void Vigenere()    /*维吉利亚密码*/
{
        char c[100], key[100];
        int lenc, lenk, i=0, j=0, tmp;
        clrscr();

        printf("********Vigenere Cipher********\nPlease input primal sentence: ");
        gets(c);
        lenc = strlen(c);
        strcpy(c, strupr(c));
        printf("Input the key: ");
        gets(key);
        lenk = strlen(key);
        strcpy(key, strupr(key));
        for(; i<lenc; i++)
        {
            j = j%lenk;
            if(c[i]>64&&c[i]<91)
            {
                c[i] = (c[i]-65+key[j]-65)%26+65;
                j++;
            }
        }
        printf("Result is: %s\n", c);
        for(i=0, j=0; i<lenc; i++)
        {
            j = j%lenk;
            if(c[i]>64&&c[i]<91)
            {
                tmp = c[i]-65-(key[j]-65);
                if(tmp>=0)
                    c[i] = tmp%26+97;
                else
                    c[i] = (tmp+26)%26+97;
                j++;
            }
        }
        printf("\nAfter translated the sentence,we can see the primal sentence as follow:\n%s\n", c);
        printf("Press any key to return...");
        getch();
}

void Permutation() /*置换密码*/
{
        char c[100], *q;
        int *key, len, m, i, j=0;
        clrscr();

        printf("********Permutation Cipher********\nPlease input primal sentence: ");
        gets(c);
        strcpy(c, strupr(c));
        len = strlen(c);
        for(i=0; i<len; i++)
        {
            if(c[i]<65||c[i]>90)
            {
                for(j=i; j<len-1; j++)
                    c[j] = c[j+1];
                len--;
            }
        }
        c[len] = '\0';
        printf("Input the length of the key: ");
        scanf("%d", &m);
        key = (int)malloc(m*sizeof(int));
        q = (int)malloc(len*sizeof(int));
        printf("Input the key: ");
        for(i=0; i<m; i++)
        {
            scanf("%d", key+i);
            key[i]--;
        }
        getchar();

        for(i=0; i<len; i++)
        {
            j = (i/m)*m;
            q[i] = c[*(key+i%m)+j];
        }
        q[i] = '\0';

        printf("Result is: %s\n", q);

        for(i=0, j=0; i<len; i++)
        {
            j = (i/m)*m;
            c[*(key+i%m)+j] = q[i]+32;
        }
        c[len] = '\0';

        printf("After translated the sentence,we can see the primal sentence as follow:\n%s\n", c);
        printf("Press any key to return...");
        free(key);
        free(q);
        getch();
}

void main()
{
    char i = '0';
    clrscr();

    while(i!='5')
    {
        clrscr();
        printf("********Press 1~5 to choose:********\n");
        printf("1.  Shift Cipher\n2.  Affine Cipher\n3.  Vigenere Cipher\n4.  Permutation Cipher\n5.  Exit\n");
        i = getch();
        if(i=='1')
            Shift();
        else if(i=='2')
            Affine();
        else if(i=='3')
            Vigenere();
        else if(i=='4')
            Permutation();
        else if(i=='5')
            break;
    }
}