void BCipher::verify_signature(std::string content,std::string signature){
std::cout<<"Receiver verifies signature using sender's publickey"<<std::endl;
RSA::PublicKey rsaPublickey;
{
FileSource input("sender_public.dat", true);
rsaPublickey.BERDecode(input);
}
RSASSA_PKCS1v15_SHA_Verifier verifier(rsaPublickey);
StringSource ss4(content + signature, true,
new SignatureVerificationFilter(
verifier, NULL,
SignatureVerificationFilter::THROW_EXCEPTION
) // SignatureVerificationFilter
); // StringSource
std::cout << "Verified signature on message" << std::endl;
}
void BCipher::decrypt(std::string fkfile,std::string filename,std::string encryptedfile,std::string decryptedfile,std::string content,std::string signature){
AutoSeededRandomPool rng;
RSA::PrivateKey privateKey;
{
FileSource input("receiver_private.dat", true);
privateKey.BERDecode(input);
}
RSA::PublicKey publicKey;
{
FileSource input("receiver_public.dat", true);
publicKey.BERDecode(input);
}
//InvertibleRSAFunction params;
//params.GenerateRandomWithKeySize(rng, 3072);
//RSA::PrivateKey privateKey(params);
//RSA::PublicKey publicKey(params);
std::cout<<"Sending public key to sender..."<<std::endl;
std::string plain, cipher, recovered, cipher1,hmaccontents;
std::stringstream ss;
//read key file
std::ifstream infk(fkfile.c_str());
ss << infk.rdbuf();
std::string fk = ss.str();
ss.str("");
infk.close();
plain=fk;
//read HMAC file
std::ifstream inmd5(("hmac_"+encryptedfile).c_str());
ss << inmd5.rdbuf();
//std::string hmaccontents = ss.str();
std::string hmac = ss.str();
ss.str("");
inmd5.close();
// Encryption
std::cout<<"User encrypting key and HMAC of uploaded file with public key..."<<std::endl;
RSAES_OAEP_SHA_Encryptor e(publicKey);
StringSource ss1(plain, true,
new PK_EncryptorFilter(rng, e,
new StringSink(cipher)
) // PK_EncryptorFilter
); // StringSource
StringSource ss3(hmac, true,
new PK_EncryptorFilter(rng, e,
new StringSink(cipher1)
) // PK_EncryptorFilter
); // StringSource
std::cout<<"Encryption Complete.\nSender now sharing the encrypted key and HMAC of uploaded file over unsecure channel..."<<std::endl;
std::ofstream encrtptedkey("ekey.txt");
encrtptedkey << cipher;
encrtptedkey.close();
std::ofstream encrtptedhmac("ehmac_efile.txt");
encrtptedhmac << cipher1;
encrtptedhmac.close();
std::cout<<"Peer receives the encrypted files."<<std::endl;
std::cout<<"Decrypting the files using his private key..."<<std::endl;
// Decryption
RSAES_OAEP_SHA_Decryptor d(privateKey);
StringSource ss2(cipher, true,
new PK_DecryptorFilter(rng, d,
new StringSink(recovered)
) // PK_DecryptorFilter
); // StringSource
StringSource ss4(cipher1, true,
new PK_DecryptorFilter(rng, d,
new StringSink(hmaccontents)
) // PK_DecryptorFilter
); // StringSource
fk=recovered;
std::cout<<"====================================================================="<<std::endl;
//check if file is what I want.
authorize(filename);
std::cout<<"====================================================================="<<std::endl;
// verify digital signature.
verify_signature(content,signature);
std::cout<<"====================================================================="<<std::endl;
Hexa b;
std::string hmackey = fk.substr(AES::MAX_KEYLENGTH*2 + AES::BLOCKSIZE*2,HMAC_KEYLENGTH*2);
std::string skey = fk.substr(0,AES::MAX_KEYLENGTH*2);
std::string siv = fk.substr(AES::MAX_KEYLENGTH*2,AES::BLOCKSIZE*2);
//std::cout<<hmackey<<std::endl;
//std::cout<<skey<<std::endl;
//std::cout<<siv<<std::endl;
// Get key in byte form from hex
byte *key=b.hex_to_byte_decoder(skey);
// Get iv in byte form from hex
byte *iv=b.hex_to_byte_decoder(siv);
// Get cipher text from file
std::ifstream in(encryptedfile.c_str());
ss << in.rdbuf();
std::string input=ss.str();
size_t len = input.length();
int ctlen = len/2;
ss.str("");
in.close();
std::cout<<"Checking HMAC of downloaded file ..."<<std::endl;
HashMac h;
if(h.verify_hmac(hmackey,input,hmaccontents)){
std::cout<<"File authenticated and integrity maintained!"<<std::endl;
}
else{
std::cout<<"File could not be authenticated!"<<std::endl;
return;
}
// Convert ciphertext to bytes from hex
byte *ciphertext=b.hex_to_byte_decoder(input);
unsigned char *plaintext = new unsigned char[ctlen+1];
plaintext[ctlen]='\0';
std::cout<<"====================================================================="<<std::endl;
// Decrypt the file and store contents to file
CFB_Mode<AES>::Decryption cfbDecryption(key, AES::MAX_KEYLENGTH, iv);
cfbDecryption.ProcessData(plaintext, ciphertext, ctlen+1);
std::string x = b.byte_to_hex_encoder(plaintext,ctlen);
std::ofstream outfinal(decryptedfile.c_str());
outfinal << x;
outfinal.close();
std::cout<<"Succeed! You can check file_recovered.txt"<<std::endl;
}