rsa2.txt

公钥密码！主要是实现文件的加密和解密功能

/*RSA algorithm */ 
#include <stdio.h> 
#include <string.h> 
#include <stdlib.h> 
#define MM 7081 
#define KK 1789 
#define PHIM 6912 
#define PP 85 
typedef char strtype[10000]; 
int len; 
long nume[10000]; 
int change[126]; 
char antichange[37]; 

void initialize() 
{ int i; 
char c; 
for (i = 11, c = 'A'; c <= 'Z'; c ++, i ++) 
{ change[c] = i; 
antichange[i] = c; 
} 
} 
void changetonum(strtype str) 
{ int l = strlen(str), i; 
len = 0; 
memset(nume, 0, sizeof(nume)); 
for (i = 0; i < l; i ++) 
{ nume[len] = nume[len] * 100 + change[str[i]]; 
if (i % 2 == 1) len ++; 
} 
if (i % 2 != 0) len ++; 
} 
long binamod(long numb, long k) 
{ if (k == 0) return 1; 
long curr = binamod (numb, k / 2); 
if (k % 2 == 0) 
return curr * curr % MM; 
else return (curr * curr) % MM * numb % MM; 
} 
long encode(long numb) 
{ return binamod(numb, KK); 
} 
long decode(long numb) 
{ return binamod(numb, PP); 
} 
main() 
{ strtype str; 
int i, a1, a2; 
long curr; 
initialize(); 
puts("Input 'Y' if encoding, otherwise input 'N':"); 
gets(str); 
if (str[0] == 'Y') 
{ gets(str); 
changetonum(str); 
printf("encoded: "); 
for (i = 0; i < len; i ++) 
{ if (i) putchar('-'); 
printf(" %ld ", encode(nume[i])); 
} 
putchar('\n'); 
} 
else 
{ scanf("%d", &len); 
for (i = 0; i < len; i ++) 
{ scanf("%ld", &curr); 
curr = decode(curr); 
a1 = curr / 100; 
a2 = curr % 100; 
printf("decoded: "); 
if (a1 != 0) putchar(antichange[a1]); 
if (a2 != 0) putchar(antichange[a2]); 
} 
putchar('\n'); 
} 
putchar('\n'); 
system("PAUSE"); 
return 0; 
}