如何将图像读取到字符串以加密Crypto ++

Question

我需要将文件读取为二进制数据，然后才能对其进行加密和解密。我正在测试Crypto ++中不同算法的速度。到目前为止，我一直在使用getline来阅读文本文件。

int main( int argc, char* argv[] ) {
string plaintext, ciphertext, encoded, recovered, sample_files_path, data_file, line_contents, file_size; 

ifstream initial_file_contents ( "1MB.txt");
if (initial_file_contents.is_open()) {
    plaintext = "";
    while ( getline( initial_file_contents, line_contents ) ) {
        plaintext = plaintext + line_contents;
        plaintext.push_back('\n');
        initial_file_contents.close();
    }
} else {
    cout << "Unable to open file" << endl;
}

/*BLOWFISH ALGORITHM*/
AutoSeededRandomPool blowfish_prng; // This class seeds itself using an operating system provided RNG
SecByteBlock blowfish_key(Blowfish::DEFAULT_KEYLENGTH); // Generate a random key
blowfish_prng.GenerateBlock(blowfish_key, blowfish_key.size()); // Generate a random initialization vector
byte blowfish_iv[Blowfish::BLOCKSIZE];
blowfish_prng.GenerateBlock(blowfish_iv, sizeof(blowfish_iv));

// Encrypts the plaintext
e.SetKeyWithIV( blowfish_key, blowfish_key.size(), blowfish_iv, sizeof(blowfish_iv) );
ciphertext.clear();
StringSource ss1(plaintext, true, new AuthenticatedEncryptionFilter( e, new StringSink( ciphertext ) )  ); 

// Decrypts the test
EAX< Blowfish >::Decryption d;
d.SetKeyWithIV( blowfish_key, blowfish_key.size(), blowfish_iv, sizeof(blowfish_iv) );
recovered.clear();
StringSource ss2(ciphertext, true, new AuthenticatedDecryptionFilter( d, new StringSink( recovered ), AuthenticatedDecryptionFilter::THROW_EXCEPTION ) ); 
return 0;
}

我见过其他文章，例如Reading an image file in C/C++和Read a binary file (jpg) to a string using c++，但我不确定该怎么做。我觉得http://www.cplusplus.com/reference/istream/istream/read/可能是一个很好的例子，但我仍然不确定如何实现它。有人可以告诉我如何读取.jpg文件等文件，并将其存储为字符串，以便加密吗？

如果我有一个名为image.jpg的文件，我怎么读它才能像明文一样在字符串变量中？

Answer 1

使用FileSource和FileSink。它避免将数据读入像string这样的中间对象，但在某些情况下可能会更有效。

AutoSeededRandomPool prng;

SecByteBlock key(Blowfish::DEFAULT_KEYLENGTH);
prng.GenerateBlock( key, key.size() );

byte iv[ Blowfish::BLOCKSIZE ];
prng.GenerateBlock( iv, sizeof(iv) );

string ofilename = "puppy-and-teddy-orig.jpg";
string efilename = "puppy-and-teddy.enc";
string rfilename = "puppy-and-teddy-recovered.jpg";

try {

    /*********************************\
    \*********************************/

    EAX< Blowfish >::Encryption e1;
    e1.SetKeyWithIV(key, key.size(), iv, sizeof(iv));

    FileSource fs1(ofilename.c_str(), true,
                   new AuthenticatedEncryptionFilter(e1,
                       new FileSink(efilename.c_str())
                   ) );

    /*********************************\
    \*********************************/

    EAX< Blowfish >::Decryption d2;
    d2.SetKeyWithIV( key, key.size(), iv, sizeof(iv) );

    FileSource fs2(efilename.c_str(), true,
                   new AuthenticatedDecryptionFilter( d2,
                       new FileSink( rfilename.c_str() ),
                       AuthenticatedDecryptionFilter::THROW_EXCEPTION
                   ) );

} catch (const Exception& ex) {
    cerr << ex.what() << endl;
}

这是图像：

这里是十六进制编辑器下的加密图像：

运行它在原始图像和恢复图像之间没有区别：

$ ./cryptopp-test.exe
$ diff puppy-and-teddy-orig.jpg puppy-and-teddy-recovered.jpg 
$

---

如果确实希望将其读入字符串，则以下是相关更改：

std::ifstream ifile("puppy-and-teddy-orig.jpg", ios::binary);
std::ifstream::pos_type size = ifile.seekg(0, std::ios_base::end).tellg();
ifile.seekg(0, std::ios_base::beg);

string temp;
temp.resize(size);
ifile.read((char*)temp.data(), temp.size());

/*********************************\
\*********************************/

EAX< Blowfish >::Encryption e1;
e1.SetKeyWithIV(key, key.size(), iv, sizeof(iv));

StringSource ss1(temp, true,
                 new AuthenticatedEncryptionFilter( e1,
                     new FileSink(efilename.c_str())
                 ) );

/*********************************\
\*********************************/

EAX< Blowfish >::Decryption d2;
d2.SetKeyWithIV( key, key.size(), iv, sizeof(iv) );

FileSource fs2(efilename.c_str(), true,
               new AuthenticatedDecryptionFilter(d2,
                   new FileSink(rfilename.c_str()),
                   AuthenticatedDecryptionFilter::THROW_EXCEPTION
               ) );