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/*
* SimpleCrypt
* Non-ECB version
* So simple it's all one function.
*
* Nathan Lasseter (User_4574)
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char** argv) {
// We need a file to encrypt
if (argc != 2) {
fprintf(stderr, "Usage: encrypt <file>\n");
return EXIT_FAILURE;
}
// Now lets open that file
FILE* file = fopen(argv[1], "r");
if (file == NULL) {
fprintf(stderr, "No such file\n");
return EXIT_FAILURE;
}
// Now we need the passphrase. Get it
char *passphrase = malloc(256);
do {
printf("Enter Passphrase: ");
if (fgets(passphrase, 255, stdin) == NULL) {
fclose(file);
fprintf(stderr, "Read error or end of file\n");
return EXIT_FAILURE;
}
} while (strlen(passphrase) <= 0);
// And a temporary file to hold the encrypted data
char tpath[] = ".SimCr.XXXXXX";
int tempfd = mkstemp(tpath);
FILE* temp = fdopen(tempfd, "w");
// Now we decrypt!
int passlen = strlen(passphrase) - 2;
int c, d, j = 0;
while ((c=fgetc(file)) != EOF) {
d = c - passphrase[j];
passphrase[j] = c;
fputc(d, temp);
if (j == passlen) j=0;
else j++;
}
// Close the files
fflush(temp);
fclose(temp);
fclose(file);
// Free used memory
free(passphrase);
// Move the file back
if (rename(tpath, argv[1]) != 0) {
fprintf(stderr, "Your encrypted file is located in %s.", tpath);
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
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