异或加解密

// Description:
// By Sarah Dean
// Email: sdean12@sdean12.org
// WWW:   http://www.FreeOTFE.org/
//
// -----------------------------------------------------------------------------
//


#include <stdio.h>

#define SECTOR_SIZE 512






// Dump out to "stream" a pretty-printed hex dump of the memory from "data"
// Not perfect, but hey, it'll do for now...
// If dataLength%columns != 0, you may get the ASCII on the last line in
// the wrong place
//
// stream - the stream to which the pretty-printed dump should be sent
// data - pointer to the data to be pretty-printed
// dataLength - amount of data to be dumped out (in bytes)
// columns - number of columns to be used in pretty-printing the hexdump
// indent - pointer to a string to be printed at the start of each line
void HexDump(FILE *stream, const unsigned char *data, int dataLength, int columns, char *indent)
{
    int i;
    int j;
    // Print column numbers
    fprintf(stream, "%s   | ", indent);

    for (j = 0; j < columns; j++) {
        fprintf(stream, "%02x ", j);
    }

    fprintf(stream, "  ASCII\n");
    // Print line under column numbers
    fprintf(stream, "%s---+-", indent);

    for (j = 0; j < columns; j++) {
        fprintf(stream, "---");
    }

    fprintf(stream, "-------\n");

    // Print out nicely formatted data
    for (i = 0; i < dataLength; i = i + columns) {
        fprintf(stream, "%s%02x | ", indent, i);

        // Hex representation
        for (j = 0; j < columns; j++) {
            fprintf(stream, "%02x ", data[i + j]);
        }

        fprintf(stream, "  ");

        // ASCII representation (where possible)
        for (j = 0; j < columns; j++) {
            // Print char if it's printable, otherwise print a "."
            if (((data[i + j]) >= ' ') && ((data[i + j]) <= '~')) {
                fprintf(stream, "%c", data[i + j]);
            } else {
                fprintf(stream, ".");
            }
        }

        fprintf(stream, "\n");
    }
}




void main(void)
{
    FILE *inFile;
    FILE *outFile;
    unsigned char inBuf[SECTOR_SIZE];
    unsigned char outBuf[SECTOR_SIZE];
    unsigned char* inBufPtr;
    unsigned char* outBufPtr;
    unsigned int x;
    unsigned int i;
    int cipher;
    // 20 * 8 = 160 bits
    // - it should be 20, not 32
    unsigned char key[32];
    unsigned char keyIdx;
    unsigned int keyBytes;
    // Blank out key; ensures data beyond end of buffer is zero'd
    memset(key, 0, sizeof(key));
    key[ 0] = 'p';
    key[ 1] = 'a';
    key[ 2] = 's';
    key[ 3] = 's';
    key[ 4] = 'w';
    key[ 5] = 'o';
    key[ 6] = 'r';
    key[ 7] = 'd';
    keyBytes = 8;  // In *bytes*
    inFile = fopen("inFile.dat", "rb");

    if (inFile == NULL) {
        printf("Unable to open inFile file\n");
        exit(-1);
    }

    outFile = fopen("outFile.dat", "wb");

    if (outFile == NULL) {
        printf("Unable to open outFile file\n");
        exit(-1);
    }

    printf("Sector size: %d\n", SECTOR_SIZE);

    // Main loop
    while (!feof(inFile)) {
        x = fread(inBuf, 1, SECTOR_SIZE, inFile);

        if (x > 0) {
            printf("Bytes read: %d\n", x);

            // Pad out, if needed
            if (x < SECTOR_SIZE) {
                // Zero out any part of the unused buffer
                // This *shouldn't* be needed - it depends on the cypher implementation,
                // and whether it reads beyond the data supplied to it
                memset(&inBuf[x], 0, (SECTOR_SIZE - x));
            }

            inBufPtr = inBuf;
            outBufPtr = outBuf;

            if (keyBytes < 1) {
                memcpy(outBuf, inBuf, SECTOR_SIZE);
            } else {
                keyIdx = 0;

                for (i = 0; i < SECTOR_SIZE; i++) {
                    outBufPtr[i] = inBufPtr[i] ^ key[keyIdx];
                    // Increment key ptr, ready for next...
                    keyIdx++;

                    if (keyIdx >= keyBytes) {
                        keyIdx = 0;
                    }
                }
            }

            HexDump(stdout, (const unsigned char*)outBuf, 64, 8, (char *)"");
            fwrite(outBuf, 1, SECTOR_SIZE, outFile);
            //exit(1);
        }
    }  // while (!feof(inFile))

    fclose(inFile);
    fclose(outFile);
}