int main(int argc, char **argv)
{
extern int opterr, optind;
extern char *optarg;
int c, fd, many, first;
char *fn;
long lines = 10;
setlocale(LC_ALL, "");
opterr = 0;
while ((c = getopt(argc, argv, "n:")) != -1)
switch (c)
{
case 'n':
if (*optarg && (lines = ctol(optarg)) > 0)
break;
/* else fall through */
default:
fprintf(stderr, USAGE);
exit(1);
}
if (optind >= argc)
headfile(STDIN_FILENO, "stdin", lines);
else
{
many = (optind + 1 < argc) ? 1 : 0;
first = 1;
while (optind < argc)
{
fn = argv[optind++];
if (many)
{
if (first)
first = 0;
else
printf("\n");
printf("==> %s <==\n", fn);
}
if (strcmp(fn, "-") == 0)
headfile(STDIN_FILENO, "stdin", lines);
else
if ((fd = open(fn, O_RDONLY)) == -1)
error(fn);
else
{
headfile(fd, fn, lines);
if (close(fd) == -1)
error(fn);
}
}
}
return(exitstatus);
}
/**
* Encrypts a plaintext string
* @param plaintext - the plaintext string
* @return - the encrypted ciphertext string
*/
string DES::encrypt(const string& plaintext)
{
//LOGIC:
//1. Check to make sure that the block is exactly 8 characters (i.e. 64 bits)
//2. Declare an array DES_LONG block[2];
//3. Use ctol() to convert the first 4 chars into long; store the result in block[0]
//4. Use ctol() to convert the second 4 chars into long; store the resul in block[1]
//5. Perform des_encrypt1 in order to encrypt the block using this->key (see sample codes for details)
//6. Convert the first ciphertext long to 4 characters using ltoc()
//7. Convert the second ciphertext long to 4 characters using ltoc()
//8. Save the results in the resulting 8-byte string (e.g. bytes[8])
//9. Convert the string (e.g. bytes[8]) to a C++ string.
//10.Return the C++ string
string ptext = plaintext;
size_t number_of_padding = 0;
while (ptext.size() < 8)
{
ptext.append("0");
number_of_padding++;
}
// convert int to a character in ASCII
char number_of_padding_char = '0' + number_of_padding;
/**
* put the number of padding at the end of padded plaintext block
* pad only one zero may be a special case?
* std::string.back() should not be used on the empty string
* it's important to do the bound checking when dealing with end of string
* we will remove the padding in the cipher.cpp
*/
if (number_of_padding > 0 && number_of_padding < 8) {
size_t last_index = ptext.length() - 1;
ptext.at(last_index) = number_of_padding_char;
}
DES_LONG block[2];
//Convert C++ string to c-string
char cstr1[4];
char cstr2[4];
ptext.copy(cstr1, 4, 0);
cstr1[4] = '\0';
ptext.copy(cstr2, 4, 4);
cstr2[4] = '\0';
unsigned char ucstr1[4];
memset(ucstr1, 0, sizeof(ucstr1));
for (int i = 0; i < sizeof(cstr1); i++) {
ucstr1[i] = cstr1[i];
}
ucstr1[sizeof(cstr1)] = '\0';
unsigned char ucstr2[4];
memset(ucstr2, 0, sizeof(ucstr2));
for (int i = 0; i < sizeof(cstr2); i++) {
ucstr2[i] = cstr2[i];
}
ucstr2[sizeof(cstr2)] = '\0';
//Convert first 4 chars into Long Int
block[0] = ctol(ucstr1);
block[1] = ctol(ucstr2);
//Encrypt
des_encrypt1(block,key,ENC);
//Convert long to c string
unsigned char txtText1[4];
unsigned char txtText2[4];
ltoc(block[0], txtText1);
ltoc(block[1], txtText2);
//Convert c string to C++ string
string convertcstr1 = "";
for (int i = 0; i < sizeof(txtText1); i++) {
convertcstr1.push_back(txtText1[i]);
}
string convertcstr2 = "";
for (int i = 0; i < sizeof(txtText2); i++) {
convertcstr2.push_back(txtText2[i]);
}
//cout << "ciphertext: " << convertcstr1 + convertcstr2 << endl;
//cout << "decrypt test: " << decrypt(convertcstr1 + convertcstr2) << "|" << endl;
return convertcstr1 + convertcstr2;
}
/**
* Decrypts a string of ciphertext
* @param ciphertext - the ciphertext
* @return - the plaintext
*/
string DES::decrypt(const string& ciphertext)
{
//LOGIC:
// Same logic as encrypt(), except in step 5. decrypt instead of encrypting
DES_LONG block[2];
//Convert C++ string to c-string
/*const char* cstrText1 = ciphertext.substr(0,4).c_str();
const char* cstrText2 = ciphertext.substr(4,4).c_str();
char cstr1[4], cstr2[4];
strncpy (cstr1, cstrText1, sizeof(cstrText1));
strncpy (cstr2, cstrText2, sizeof(cstrText2));
*/
char cstr1[4];
char cstr2[4];
ciphertext.copy(cstr1, 4, 0);
cstr1[4] = '\0';
ciphertext.copy(cstr2, 4, 4);
cstr2[4] = '\0';
unsigned char ucstr1[4];
memset(ucstr1, 0, sizeof(ucstr1));
for (int i = 0; i < sizeof(cstr1); i++) {
ucstr1[i] = cstr1[i];
}
ucstr1[sizeof(cstr1)] = '\0';
unsigned char ucstr2[4];
memset(ucstr2, 0, sizeof(ucstr2));
for (int i = 0; i < sizeof(cstr2); i++) {
ucstr2[i] = cstr2[i];
}
ucstr2[sizeof(cstr2)] = '\0';
//Convert first 4 chars into Long Int
block[0] = ctol(ucstr1);
block[1] = ctol(ucstr2);
//Decrypt
des_encrypt1(block,key,DEC);
//Convert Long back to c string
unsigned char txtText1[4];
unsigned char txtText2[4];
ltoc(block[0], txtText1);
ltoc(block[1], txtText2);
//Convert c string to C++ string
string convertcstr1 = "";
for (int i = 0; i < sizeof(txtText1); i++) {
convertcstr1.push_back(txtText1[i]);
}
string convertcstr2 = "";
for (int i = 0; i < sizeof(txtText2); i++) {
convertcstr2.push_back(txtText2[i]);
}
//cout << "length of plaintext: " << test.length() << endl;
return convertcstr1 + convertcstr2;
}
