Hi
I am trying to create a simple transformation that will be pipelined,
however I think I may be approaching this all wrong. Basically I am
looking to (ideally) pass a key (or pad) to the stream and xor this
(repeating the pad if necessary up to size of data stream). Ideally
non blocking and streaming.
I have been hacking about and think I am going insane doing so :-)
Here is some examples of what I have been attempting. Please feel free
to ignore and provide an example of this. Problem seem to perhaps be
passing the pad or key into the XOR stream, that plus the fact I am
trying to get used to the library and language. Sorry if it seems a
bit on the wild side.
I am also looking to pass the xor'ed data down through a pipeline and
perhaps pass in a string pointer to be populated with a hash of the
data that was passed through the filter, either that or somehow have
more than one sink (but that seems very insane :D.
Any help / examples appreciated. I am very new to cryptopp and am not
getting time to digest all the information properly so please be
gentle.
Anyway I defined this
======================================
class XORFilter : public CryptoPP::Filter {
public:
XORFilter(CryptoPP::BufferedTransformation *attachment = NULL,
std::string pad = "", // was a pointer to start with
std::string *result_hash = NULL): Filter(attachment),
pad_(pad),
result_hash_(result_hash) {
// CryptoPP::Filter::Detach(attachment); // unsure of why this
exists in examples, need to wrap head around terminology
};
size_t Put2(const byte* inString,
size_t length,
int messageEnd,
bool blocking);
bool IsolatedFlush(bool, bool) { return false; }
private:
std::string pad_;
std::string *result_hash_;
};
==================================================
and implemented something like this (extreme messiness but you get the
point).
/**
* Implementation of XOR transformation filter to allow pipe-lining
*
*/
size_t XORFilter::Put2(const byte* inString,
size_t length,
int messageEnd,
bool blocking) {
// Anything to process? If not, we will pass it on
// to the lower filter just in case... from example
if((length == 0) || (pad_.length() < length ))
return AttachedTransformation()->Put2(inString,
length,
messageEnd,
blocking);
// Do XOR
byte *buffer;
byte *pad = new byte[length]; // assuming pad_ is == length for now
as a test
memcpy(pad, pad_.c_str(), pad_.length()); / OK dangerous but for
testing !!
//CryptoPP::xorbuf(pad, inString, length); // tried both xorbuf
methods
size_t padlength = pad_.length(); // debugging
for (size_t i = 0; i <= length; ++i) {
buffer[i] = inString[i] ^ pad[i];
}
return AttachedTransformation()->Put2(buffer,
length,
messageEnd,
blocking );
}
Anyhow, hope you can help!
David
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