hdu1211

RSA is one of the most powerful methods to encrypt data. The RSA algorithm is described as follow:

> choose two large prime integer p, q
> calculate n = p × q, calculate F(n) = (p - 1) × (q - 1)
> choose an integer e(1 < e < F(n)), making gcd(e, F(n)) = 1, e will be the public key
> calculate d, making d × e mod F(n) = 1 mod F(n), and d will be the private key

M = D(c) = c^d mod n

RSA 加密

 

#include <stdio.h>int main(){    int i,j,p,q,e,l,c,d,m;    __int64 fn,n;    while(scanf("%d%d%d%d",&p,&q,&e,&l)!=EOF)    {        n=p*q;        fn=(p-1)*(q-1);        for(i=0;;i++)            if((i*fn+1)%e==0)            {                d=(i*fn+1)/e;                break;            }          for(i=0; i<l; i++)        {            scanf("%d",&c);            m=1;            for(j=1; j<=d; j++)            {                m=(m*c)%n;            }            printf("%c",m);        }        printf("\n");    }    return 0;}