sketch.cpp

关于BCH编码的一个应用

// sketch.cpp
//
// C++ code by Kevin Harmon and Leonid Reyzin
//
// Finds the PinSketch (BCH-based secure sketch) of an input set.
//
// See pinsketch.txt for detailed documentation
//

#include "pinsketch.h"

int main(int argc, char** argv)
{
	long d; // minimum distance of the code;
		// can handle set difference up to t=(d-1)/2 elements
		// sketch is (d-1)/2 elements long

        long m; // elements of the set and of the sketch are m-bit values

	int len;// length of argv[1] if it exists


	if (argc != 2 || (len=strlen(argv[1]))<5 || strcmp(&argv[1][len-4], ".set"))
	{
		cerr << "Usage: sketch A.set" << endl;
		if (argc == 2)
			cerr << "(file must be named `*.set`)" << endl;
		return -1;
	}

// Fix field and error-tolerance
	ifstream infile(argv[1]);
        if (!infile) {
          cerr << "Could not open file for reading!\n";
          return -1;
        }
	ReadSetParams(m, d, infile);

        GF2X irrP;
	BuildSparseIrred(irrP, m); // fix irreducible poly of deg m over GF(2)
	GF2E::init(irrP); // fix field as GF(2^m)

// read in set  
	vec_GF2E set, ss;
	ReadSet(set, infile, m);
	infile.close();

// compute secure sketch of the set
	BCHSyndromeCompute(ss, set, d);

// write the sketch to file with same name and .ss extension
	strcpy(&argv[1][strlen(argv[1])-4], ".ss");
	ofstream outfile (argv[1], ios::out | ios::trunc);
        if (!outfile) {
          cerr << "Could not open file for writing!\n";
          return -1;
        }
	OutputSS(outfile, ss, d, GF2E::modulus());
	outfile.close();

	cout << "Secure sketch written to file `" << argv[1] << "`." << endl;
	
	return 0;
}