Encryption
Dear Everyone,
Can someone give me a simple example for encrypt the "Hello",
I've download the "encrypt.c", but so hard for me,
please who can give me the simple one.
Thanks.
/*
* File: encrypt.c
* Date: 8 May 1999
* Author: Bret Taylor ([email protected])
* -------------------------------------------
* This is the implementation for the encrypt.h library. This
* library uses bit manipulation to consistently map characters
* to an unreadable format that is also 8 bits in length. It does
* so with the bitwise XOR operator (^), which returns which bits
* are on in the first operand, but not in both. The useful thing
* about this operator is that a variable XOR'd with another can be
* returned to its original state simply by XORing it with that
* variable again. Hence, this library (internally, anyway) doesn't
* even make a distinction between encrypting and decrypting (both
* simply require XORing each character in the input file)!
*/
#include "encrypt.h"
#include <assert.h>
/* Private Function Prototypes */
static void ApplyKeyToFile(FILE *in, FILE *out, unsigned char key);
/*
* Public Function: EncodeFile
* ---------------------------
* This function is simply a wrapper function for the ApplyKeyToFile
* decoder/encoder function.
*/
void EncodeFile(FILE *textFile, FILE *outputFile, unsigned char key)
{
assert(textFile && outputFile);
ApplyKeyToFile(textFile, outputFile, key);
}
/*
* Public Function: DecodeFile
* ---------------------------
* This function is simply a wrapper function for the ApplyKeyToFile
* decoder/encoder function.
*/
void DecodeFile(FILE *encodedFile, FILE *outputFile, unsigned char key)
{
assert(encodedFile && outputFile);
ApplyKeyToFile(encodedFile, outputFile, key);
}
/*
* Function: ApplyKeyToFile
* ------------------------
* This function reads in characters from the in file, applying
* the bitwise XOR operator on each. It then writes those characters
* to out. Read this file's comments for a detailed explanation why
* this function makes no distinction between "encoding" and
* "decoding".
*/
static void ApplyKeyToFile(FILE *in, FILE *out, unsigned char key)
{
int ch;
while ((ch = getc(in)) != EOF)
putc(ch ^ key, out);
}
