Task 4 : The key is hardcoded in the provided source DES encryption/decryption programs. Please change the source code files of the DES encryption/decryption programs, so that the key would be entered through the command line as the 4th input argument. SOURCE CODE FOR ENCODE: #include<iostream> #include<fstream> #include<sstream> #include<string> using namespace std; #include"cryptopp/cryptlib.h" #include"cryptopp/hex.h" #include"cryptopp/filters.h" #include"cryptopp/des.h" #include"cryptopp/modes.h" using namespace CryptoPP; string des_encode(string & plain,byte key[]) { string cipher; try { //cout << "plain text: " << plain << endl; ECB_Mode<DES>::Encryption enc; enc.SetKey(key, DES::DEFAULT_KEYLENGTH); StringSource(plain, true, new StreamTransformationFilter(enc, new StringSink(cipher)));//add padding by StreamTransformationFilter } catch(const CryptoPP::Exception& e) { cerr << e.what() << endl; exit(1); } return cipher; } int main(int argc, char * argv[]) { ifstream file1; ofstream file2; byte key[DES::DEFAULT_KEYLENGTH]={'1','2','3','4','a','b','c','d'}; //key is hardcoded if(argc!=3) { cout<<"usage:des_encode infile outfile" << endl; } cout << " The input file name is " << argv [1] << endl; cout << " The output file name is " << argv [2] << endl; file1.open(argv[1]); file2.open(argv[2]); //reading stringstream buffer; buffer << file1.rdbuf(); string plain(buffer.str()); //print key string encoded; encoded.clear(); StringSource(key, sizeof(key), true, new HexEncoder( new StringSink(encoded))); cout << "key: " << encoded << endl; //encrypt string cipher=des_encode(plain,key); file2<<cipher; cout<<"cipher text stored in:"<<argv[2]<<endl; file1.close(); file2.close(); return 0; } SOURCE CODE FOR DECODE: #include<iostream> #include<fstream> #include<sstream> #include<string> using namespace std; #include"cryptopp/cryptlib.h" #include"cryptopp/hex.h" #include"cryptopp/filters.h" #include"cryptopp/des.h" #include"cryptopp/modes.h" using namespace CryptoPP; string des_decode(string & cipher,byte key[]) { string plain; //decryption try { ECB_Mode< DES >::Decryption dec; dec.SetKey(key, DES::DEFAULT_KEYLENGTH); StringSource s(cipher, true, new StreamTransformationFilter(dec, new StringSink(plain))); cout << "recovered text: " << plain<< endl; } catch(const CryptoPP::Exception& e) { cerr << e.what() << endl; exit(1); } return plain; } int main(int argc,char * argv[]) { ifstream file1; ofstream file2; byte key[DES::DEFAULT_KEYLENGTH]={'1','2','3','4','a','b','c','d'}; //key is hardcoded; if(argc!=3) { cout<<"usage:des_decode infile outfile" <<endl; } cout << " The input file name is " << argv [1] << endl; cout << " The output file name is " << argv [2] << endl; file1.open(argv[1]); file2.open(argv[2]); //reading stringstream buffer; buffer << file1.rdbuf(); string cipher(buffer.str()); //print key string encoded; encoded.clear(); StringSource(key, sizeof(key), true, new HexEncoder( new StringSink(encoded))); cout << "key: " << encoded << endl; //de.

1. Task 4 : The key is hardcoded in the provided source DES encryption/decryption programs.
Please change the source code files of the DES encryption/decryption programs, so that the key
would be entered through the command line as the 4th input argument.
SOURCE CODE FOR ENCODE: #include<iostream> #include<fstream> #include<sstream>
#include<string> using namespace std; #include"cryptopp/cryptlib.h" #include"cryptopp/hex.h"
#include"cryptopp/filters.h" #include"cryptopp/des.h" #include"cryptopp/modes.h" using
namespace CryptoPP; string des_encode(string & plain,byte key[]) { string cipher; try { //cout <<
"plain text: " << plain << endl; ECB_Mode<DES>::Encryption enc; enc.SetKey(key,
DES::DEFAULT_KEYLENGTH); StringSource(plain, true, new StreamTransformationFilter(enc,
new StringSink(cipher)));//add padding by StreamTransformationFilter } catch(const
CryptoPP::Exception& e) { cerr << e.what() << endl; exit(1); } return cipher; } int main(int argc, char
* argv[]) { ifstream file1; ofstream file2; byte
key[DES::DEFAULT_KEYLENGTH]={'1','2','3','4','a','b','c','d'}; //key is hardcoded if(argc!=3) {
cout<<"usage:des_encode infile outfile" << endl; } cout << " The input file name is " << argv [1] <<
endl; cout << " The output file name is " << argv [2] << endl; file1.open(argv[1]);
file2.open(argv[2]); //reading stringstream buffer; buffer << file1.rdbuf(); string plain(buffer.str());
//print key string encoded; encoded.clear(); StringSource(key, sizeof(key), true, new HexEncoder(
new StringSink(encoded))); cout << "key: " << encoded << endl; //encrypt string
cipher=des_encode(plain,key); file2<<cipher; cout<<"cipher text stored in:"<<argv[2]<<endl;
file1.close(); file2.close(); return 0; }
SOURCE CODE FOR DECODE: #include<iostream> #include<fstream> #include<sstream>
#include<string> using namespace std; #include"cryptopp/cryptlib.h" #include"cryptopp/hex.h"
#include"cryptopp/filters.h" #include"cryptopp/des.h" #include"cryptopp/modes.h" using
namespace CryptoPP; string des_decode(string & cipher,byte key[]) { string plain; //decryption try {
ECB_Mode< DES >::Decryption dec; dec.SetKey(key, DES::DEFAULT_KEYLENGTH);
StringSource s(cipher, true, new StreamTransformationFilter(dec, new StringSink(plain))); cout <<
"recovered text: " << plain<< endl; } catch(const CryptoPP::Exception& e) { cerr << e.what() <<
endl; exit(1); } return plain; } int main(int argc,char * argv[]) { ifstream file1; ofstream file2; byte
key[DES::DEFAULT_KEYLENGTH]={'1','2','3','4','a','b','c','d'}; //key is hardcoded; if(argc!=3) {
cout<<"usage:des_decode infile outfile" <<endl; } cout << " The input file name is " << argv [1] <<
endl; cout << " The output file name is " << argv [2] << endl; file1.open(argv[1]);
file2.open(argv[2]); //reading stringstream buffer; buffer << file1.rdbuf(); string cipher(buffer.str());
//print key string encoded; encoded.clear(); StringSource(key, sizeof(key), true, new HexEncoder(
new StringSink(encoded))); cout << "key: " << encoded << endl; //decryption; string
plain=des_decode(cipher,key); file2<<plain; cout<<"plain text stored in:"<<argv[2]<<endl;
file1.close(); file2.close(); return 0; }