RSDecoder< F, vec_F, FX, FXY, mat_F > Class Template Reference

Reed-Solomon Decoder. More...

#include <rsdecoder.h>

Public Member Functions
	RSDecoder ()
	GF2E Constructor. More...
	RSDecoder (const ZZ &p1, const ZZ &p2)
	ZZ_p Constructor. More...
bool	Recover (dbsize_t bytes_per_word, nservers_t t, nservers_t h, const vector< nservers_t > &goodservers, const vector< vector< vec_F > > &values, const vec_F &server_indices, vector< vector< DecoderResult< F > > > &results, vector< std::set< dbsize_t > > &decoded, const vector< vec_F > &vec_interp_indices, const nqueries_t multi_only=0)
	The main method to do the Reed-Solomon Decoding. More...

Static Public Member Functions
static string	append (const string &s, const F &wz, unsigned int bytes_per_word)
	A helper function to append an element of F to a string. More...
static void	test_interpolate (unsigned short t, const vec_F &values, const vec_F &indices, const vector< unsigned short > &I, const vector< unsigned short > &G, unsigned short &numagree, unsigned short &numdisagree, vector< unsigned short > &vecagree, FX &phi)
	Interpolate some points I and check how many points G agree with the result. More...

Detailed Description

template<class F, class vec_F, class FX, class FXY, class mat_F>
class RSDecoder< F, vec_F, FX, FXY, mat_F >

Reed-Solomon Decoder.

The main RSDecoder class, genericized to work over different types of fields.

Template Parameters

F	The field used for decoding.
vec_F	Vectors over the field F.
FX	Univariate polynomials over the field F.
FXY	Bivariate polynomials over the field F.
mat_F	Matrices over the field F.

Constructor & Destructor Documentation

RSDecoder ( )

inline

GF2E Constructor.

Call this constructor for GF2E. Be sure to call GF2E::init as well, with an appropriate polynomial modulus.

RSDecoder ( const ZZ &  p1, const ZZ &  p2  )

inline

ZZ_p Constructor.

Call this constructor for ZZ_p. p2 should be prime, and p1 should be either prime or 1. The modulus used is p1*p2.

Member Function Documentation

static string append ( const string &  s, const F &  wz, unsigned int  bytes_per_word  )

static

A helper function to append an element of F to a string.

It's public and static so that EasyRecover can use it.

Parameters

s	The string to append to.
wz	The fields element to append to the string.
bytes_per_word	The number of bytes each word uses.

Returns

The string s appended with wz.

bool Recover	(	dbsize_t	bytes_per_word,
		nservers_t	t,
		nservers_t	h,
		const vector< nservers_t > &	goodservers,
		const vector< vector< vec_F > > &	values,
		const vec_F &	server_indices,
		vector< vector< DecoderResult< F > > > &	results,
		vector< std::set< dbsize_t > > &	decoded,
		const vector< vec_F > &	vec_interp_indices,
		const nqueries_t	multi_only = 0
	)

The main method to do the Reed-Solomon Decoding.

Parameters

bytes_per_word	The number of bytes each word uses.
t	The privacy level. I.e. the maximum number of servers that can collude without breaking privacy.
h	The number of honest servers.
goodservers	The indices of the servers that did not act up.
values	The server shares. Indexed by query then by word.
server_indices	The indices used for server shares.
results	The decoding results for each query. Will be filled as decoding occurs.
decoded	For each query, the words that have been successfully decoded. Will be updated as decoding occurs.
vec_interp_indices	The indices corresponding to each block requested.
multi_only	The number of queries that should only be processed using multi-query decoding. The first multi_only queries were previously attempted, were not successfully decoded and were saved for multi-query decoding.

Returns

Return true if all queries were decoded, false otherwise.

void test_interpolate ( unsigned short  t, const vec_F &  values, const vec_F &  indices, const vector< unsigned short > &  I, const vector< unsigned short > &  G, unsigned short &  numagree, unsigned short &  numdisagree, vector< unsigned short > &  vecagree, FX &  phi  )

static

Interpolate some points I and check how many points G agree with the result.

Set phi to the degree-t polynomial which interpolates the (indices,values) pairs indexed by I. Check which (indices,values) pairs indexed by G agree and disagree with phi, and set numagree, numdisagree, and vecagree accordingly.

Parameters

t	The degree of the interpolating polynomial.
values	The values of the points.
indices	The indices of the points.
I	The indices of the points to interpolate.
G	The indices of the points to check with phi.
numagree	Number of points in G that agree with phi.
numdisagree	Number of points in G that do not agree with phi.
vecagree	The indices of the points in G that agree with phi.
phi	The interpolant.

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The documentation for this class was generated from the following files:

• rsdecoder.h
• rsdecoder_impl.h