Re: Problem with Serpent Encrypt and Decrypt a File

[Dariusz Chilimoniuk]

Hi

Look into help (on-line). There is an example how use crypt functions.
Anyway, some time or other I made two a very simple programs. One for
encrypt and one for decrypt. I hope this will be useful for you. Just
change CBC_Mode<AES> to CBC_Mode<Serpent>, other things with 'AES'
keyword and also add a new #include.


Regards

-----
/*
ENCRYPTING FILES

- SZYFROWANIE PLIKOW
- Dariusz Chilimoniuk http://www.elwizard.com 18-VII-2003

- Program demonstruje uzycie klas FileSource, FileSink,
- StreamTransformationFilter, CBC_Mode<T>, SHA256, ArraySink,
- StringSource, HashFilter, AutoSeededRandomPool
- do budowy programu szyfrujacego
*/

//#include "stdafx.h"

#include "filters.h"
#include "files.h"
#include "sha.h"
#include "modes.h"
#include "aes.h"
#include "mars.h"
#include "osrng.h"

#include <iostream>
#include <cstring>


USING_NAMESPACE(CryptoPP)
USING_NAMESPACE(std)

int main()
{
       byte pass[ SHA256::DIGESTSIZE ];// digest of password
       byte iv[ AES::BLOCKSIZE ];// Initial Vector (IV)
       byte block[ AES::BLOCKSIZE ];// auxliary buffer

       AutoSeededRandomPool *rng;
       rng = new AutoSeededRandomPool;// random number generator

       string file, password;

       cout << "*** ENCRYPT ***\nType file name: " << endl;
       getline(cin, file);

       cout << "Enter password: ";
       getline(cin, password);// of corse it is not secure solution

       // digest password
       delete new StringSource( password, true,
               new HashFilter(*(new SHA256), new
ArraySink(pass,SHA256::DIGESTSIZE)) );

       // random Initial Vector
       rng->GenerateBlock(iv, AES::BLOCKSIZE);

       // create object for encrypting
       StreamTransformationFilter *encryptor;
       encryptor = new StreamTransformationFilter(
                                       *new
CBC_Mode<AES>::Encryption(pass, AES::DEFAULT_KEYLENGTH, iv),
                                       new FileSink(
(file+".encrypt").c_str() ) );

       //HEADER OF ENCRYPTED FILE:
       // 3 special blocks
       // (It works only with CBC mode)
       //
       // Let explain a little:
       //   Encrypt process:
       //    (a) get random IV;
       //    (b) encrypt 3 special blocks:
       //       - block1 and block2 are filled random data,
       //       - block3 contain the same data what are in block2
       //
       //   Decrypt process:
       //    (a) decrypt first three blocks (IV is unimportant);
       //    (b) if block2 is equal with block3 then password is correct and
       //         continue decrypting
       rng->GenerateBlock(block, AES::BLOCKSIZE);
       encryptor->Put(block, AES::BLOCKSIZE);// block1
       rng->GenerateBlock(block, AES::BLOCKSIZE);
       encryptor->Put(block, AES::BLOCKSIZE);// block2
       encryptor->Put(block, AES::BLOCKSIZE);// block3

       delete rng;

       // "bind" a file and encrypt one
       delete new FileSource(file.c_str(), true, encryptor);

       cout << "Done !" << endl;

       return 0;
}

/*
DECRYPTING FILE

- DESZYFROWANIE PLIKOW
- Dariusz Chilimoniuk http://www.elwizard.com 18-VII-2003
*/

//#include "stdafx.h"

#include "filters.h"
#include "files.h"
#include "sha.h"
#include "modes.h"
#include "aes.h"

#include <iostream>
#include <cstring>

USING_NAMESPACE(CryptoPP)
USING_NAMESPACE(std)

int main()
{
       byte pass[ SHA256::DIGESTSIZE ];
       byte iv[ AES::BLOCKSIZE ];
       byte head_file[ 3 * AES::BLOCKSIZE ];
       byte head_file_dec[ 3 * AES::BLOCKSIZE ];

       memset(iv, 0, AES::BLOCKSIZE );
       string file, file_out, password;

       cout << "*** DECRYPTING ***\nType file name: " << endl;
       getline(cin, file);

       cout << "Enter password: ";
       getline(cin, password);

       FileSource *source;
       source = new FileSource(file.c_str(), false);

       delete new StringSource( password, true,
               new HashFilter(*(new SHA256), new ArraySink(pass,
SHA256::DIGESTSIZE)) );

       CBC_Mode<AES>::Decryption *decryption;
       decryption = new  CBC_Mode<AES>::Decryption(pass, AES::DEFAULT_KEYLENGTH,
               iv);

       // checking password
               // get and encrypt 3 blocks
       source->Pump(3 * AES::BLOCKSIZE);
       source->Get(head_file, 3 * AES::BLOCKSIZE);
       decryption->ProcessBlocks(head_file_dec, head_file, 3);
               // compare block2 and block3
       if(0 != memcmp(
                       &head_file_dec[AES::BLOCKSIZE],
&head_file_dec[2*AES::BLOCKSIZE],
                       AES::BLOCKSIZE)) {
                       cout << "Bad password !" << endl;
                       return 0;
               }
       // password is correct so continue

       cout << "Type output file name:" << endl;
       getline(cin, file_out);

       // "bind" decryptor to output file
       source->Attach( new StreamTransformationFilter(*decryption,
               new FileSink(file_out.c_str()) ) );

       // push the rest data
       source->PumpAll();

       cout << "Done !" << endl;

return 0;
}
----


2005/12/30, changsengua (sent by Nabble.com) <[EMAIL PROTECTED]>:
> I am a newbie to use crypto5.0 and i have a project just want to encrypt and
> decrypt a file ,for example like .doc, .txt and so on, I face a problem is i
> cannot use the Serpent function to encrypt the whole file, can anyone give
> me the tips to do the encrypt and decrypt the file, the DES_EDE2 can
> function, but i don't know how to change it to serpent, anyone can help me?
> ________________________________
> Sent from the Crypto++ forum at Nabble.com:
> Problem with Serpent Encrypt and Decrypt a File


--
Dariusz Chilimoniuk
+48 504 228 158