XOR two files

SimpleXOR.cpp

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#define MAX_KEY_BYTE 65536

int binSize(FILE *fp) {
    fseek(fp, 0, SEEK_END); // seek to end of file
    int size = ftell(fp); // get current file pointer
    fseek(fp, 0, SEEK_SET); // seek back to beginning of file
    return size;
}

int xor_file(const char *cryptoFile, const char *keyFile, const char *outfile) {
    FILE *fpCrypto, *fpKey, *fpo;

    if ((fpCrypto = fopen(cryptoFile, "rb")) == NULL) {
        fprintf(stderr, "Cannot open crpyto file %s: %s\n", cryptoFile, strerror(errno));
        return 1;
    }
    if ((fpKey = fopen(keyFile, "rb")) == NULL) {
        fprintf(stderr, "Cannot open key file %s: %s\n", keyFile, strerror(errno));
        fclose(fpCrypto);
        return 1;
    }
    if ((fpo = fopen(outfile, "wb")) == NULL) {
        fprintf(stderr, "Cannot open output file %s: %s\n", outfile, strerror(errno));
        fclose(fpCrypto);
        fclose(fpKey);
        return 2;
    }

    int keySize = binSize(fpKey);
    char *keyBuffer = (char*)malloc(sizeof(char) * keySize);
    if (fread (keyBuffer, 1, keySize, fpKey) != keySize) {
        fprintf(stderr, "Key file is broken: %s\n", strerror(errno));
    }

    int cryptoSize = binSize(fpCrypto);
    char *cryptoBuffer = (char*)malloc(sizeof(char) * cryptoSize);
    if (fread (cryptoBuffer, 1, cryptoSize, fpCrypto) != cryptoSize) {
        fprintf(stderr, "Crypto file is broken: %s\n", strerror(errno));
    }

    for (int i = 0; i < cryptoSize; i++) {
        cryptoBuffer[i] ^= keyBuffer[i % keySize];
    }

    fwrite(cryptoBuffer, sizeof(char), cryptoSize, fpo);

    // Close
    fclose(fpCrypto);
    fclose(fpKey);
    fclose(fpo);
    free(keyBuffer);
    free(cryptoBuffer);
    return 0;
}

int main(int argc, char *argv[]) {
    if (argc == 4) {
        xor_file(argv[1], argv[2], argv[3]);
    } else {
        fprintf(stderr, "usage:key.exe <crypto_file> <key_file> <output_file>\n");
    }
    //getch();  // avoid the need for this by running your program in the terminal
    return 0;
}