Transposition Cipher Implementation > C Program

Transposition Cipher Implementation > C Program

Cryptography and System Security

Program:

#include<stdio.h>

int check(int x,int y)

{

int a,b,c;

if(x%y==0)

return 0;

a=x/y;

b=y*(a+1);

c=b-x;

return c;

}

void main()

{

int l1,i,d,j;

printf("\nEnter the length of the key. ");

scanf("%d",&l1);

int sequence[l1];

printf("\nEnter the sequence key. ");

for(i=0;i<l1;++i)

{

scanf("%d",&sequence[i]);

}

int order[l1];

for(i=1;i<=l1;++i)

{

for(j=0;j<l1;++j)

{

if(sequence[j]==i)

order[i-1]=j;

}

}

printf("\nEnter the depth. ");

scanf("%d",&d);

int l2;

printf("\nEnter the length of String without spaces . ");

scanf("%d",&l2);

int temp1=check(l2,l1);

int r=(l2+temp1)/l1;

char p[l2+temp1];

char p1[r][l1];

//char p2[r][l1];

if(temp1>0)

printf("\nYou need to enter %d bogus characters.So enter total %d characters. ",temp1,(l2+temp1));

else

printf("\nEnter the string. ");

for(i=-1;i<(l2+temp1);++i)

{

scanf("%c",&p[i]);

}

int count=0;

while(d>0)

{

count=0;

for(i=0;i<r;++i)

{

for(j=0;j<l1;++j)

{

p1[i][j]=p[count];

count=count+1;

}

}

printf("\n\n\n");

for(i=0;i<r;++i)

{

for(j=0;j<l1;++j)

{

printf("%c ",p1[i][j]);

}

printf("\n");

}

count=0;

for(i=0;i<l1;++i)

{

for(j=0;j<r;++j)

{

p[count]=p1[j][order[i]];

count=count+1;

}

}

for(i=0;i<(l2+temp1);++i)

printf("%c ",p[i]);

d=d-1;

}

}

/* OUTPUT

[prat@localhost Desktop]$ gcc transposition.c

[prat@localhost Desktop]$ ./a.out

Enter the length of the key. 7

Enter the sequence key. 4 3 1 2 5 6 7

Enter the depth. 2

Enter the length of String without spaces . 23

You need to enter 5 bogus characters.So enter total 28 characters. attackpostponeduntiltwoamxyz

a t t a c k p 

o s t p o n e 

d u n t i l t 

w o a m x y z 

t t n a a p t m t s u o a o d w c o i x k n l y p e t z 

t t n a a p t 

m t s u o a o 

d w c o i x k 

n l y p e t z 

n s c y a u o p t t w l t m d n a o i e p a x t t o k z 

*/