Implements a CipherGroup, i.e. the cartesian product of two Groups. El-Gamal operations are implemented here. More...

#include <ciphergroup.hpp>

Collaboration diagram for elGamal::CipherGroup:

Public Member Functions
	CipherGroup (arithm::Group *group)
	Builds a CipherGroup from a group in which computations will be made.
arithm::Group *	getGrp ()
	Returns the group in which the computations are made.
CipherText	getCipherText (verifierUtils::ByteTree *bt)
	Returns a CipherText from this group built from a bytetree.
ArrayOfCiphers	getArrayOfCiphers (verifierUtils::ByteTree *bt)
	Returns an ArrayOfCiphers from this group built from a bytetree.
Encryption/decryption
CipherText	enc (arithm::Elmt y, arithm::Elmt m, arithm::Elmt s)
	Let grp->getGenerator() be g then returns $Enc_{(g,y)} (m,s) = (g^s, y^s m)$ .
arithm::Elmt	dec (arithm::Elmt x, CipherText uv)
	Let uv be . Then returns $Dec_x (u,v) = u^{-x} v$ .
arithm::Elmt	pdec (arithm::Elmt xl, CipherText uv)
	Let uv be . Then returns $PDec_{x_l}(u,v) = u^{x_l}$ .
arithm::ArrayOfElmts	pdec (arithm::Elmt xl, ArrayOfCiphers uv)
	Applies pdec component-wise on an array of cipher text using a fixed public key.
arithm::Elmt	tdec (CipherText uv, arithm::Elmt f)
	Let uv be . The returns $TDec((u,v),f) = v f^{-1}$ .
arithm::ArrayOfElmts	tdec (ArrayOfCiphers uv, arithm::ArrayOfElmts f)
	Applies tdec component-wise on an array of cipher texts and an array of decryption factors (i.e. group elements).
Group operations
CipherText	exponentiation (CipherText c, arithm::Elmt s)
	Componentwise exponentiation of a ciphertext.
CipherText	multiplication (CipherText c1, CipherText c2)
	Componentwise multiplication of a ciphertext.
ArrayOfCiphers	exponentiation (ArrayOfCiphers c, arithm::ArrayOfElmts s)
	Componentwise exponentiation of an array of ciphertext.
CipherText	expProduct (ArrayOfCiphers c, arithm::ArrayOfElmts s)
	Componentwise call to Group::expProduct().
bool	compare (CipherText c1, CipherText c2)
	Returns true if c1 and c2 are identical, false otherwise.
bool	compare (ArrayOfCiphers c1, ArrayOfCiphers c2)
	Returns true if c1 and c2 contain strictly identical ciphertexts, false otherwise.

Private Attributes
arithm::Group *	grp
	The group in which computations are made.

Detailed Description

Implements a CipherGroup, i.e. the cartesian product of two Groups. El-Gamal operations are implemented here.

Definition at line 28 of file ciphergroup.hpp.

Constructor & Destructor Documentation

CipherGroup::CipherGroup ( arithm::Group * group )

Builds a CipherGroup from a group in which computations will be made.

Definition at line 20 of file ciphergroup.cpp.

{
        grp = group;
}

Member Function Documentation

bool CipherGroup::compare	(	CipherText	c1,
		CipherText	c2
	)

Returns true if c1 and c2 are identical, false otherwise.

Definition at line 131 of file ciphergroup.cpp.

{
        return (  (grp->compare(c1.getU(), c2.getU())) &&
                  (grp->compare(c1.getV(), c2.getV()))  );
}

bool CipherGroup::compare	(	ArrayOfCiphers	c1,
		ArrayOfCiphers	c2
	)

Returns true if c1 and c2 contain strictly identical ciphertexts, false otherwise.

Definition at line 138 of file ciphergroup.cpp.

{
        for (unsigned int i=0; i<c1.size(); i++)
                if (! compare(c1.getCipherText(i), c2.getCipherText(i)) )
                        return false;
        return true;
}

arithm::Elmt CipherGroup::dec	(	arithm::Elmt	x,
		CipherText	uv
	)

Let uv be $(u,v)$ . Then returns $Dec_x (u,v) = u^{-x} v$ .

Definition at line 58 of file ciphergroup.cpp.

{
        return grp->multiplication(
                grp->exponentiation(grp->multInverse(uv.getU()),x),
                uv.getV());
}

CipherText CipherGroup::enc	(	arithm::Elmt	y,
		arithm::Elmt	m,
		arithm::Elmt	s
	)

Let grp->getGenerator() be g then returns $Enc_{(g,y)} (m,s) = (g^s, y^s m)$ .

Definition at line 49 of file ciphergroup.cpp.

{
        arithm::Elmt u = grp->exponentiation(grp->getGenerator(),s);
        arithm::Elmt v = grp->multiplication(grp->exponentiation(y,s),m);
        return CipherText(u,v);
}

CipherText CipherGroup::exponentiation	(	CipherText	c,
		arithm::Elmt	s
	)

Componentwise exponentiation of a ciphertext.

Definition at line 100 of file ciphergroup.cpp.

{
        return CipherText(grp->exponentiation(c.getU(),s),
                          grp->exponentiation(c.getV(),s));
                          
}

ArrayOfCiphers CipherGroup::exponentiation	(	ArrayOfCiphers	c,
		arithm::ArrayOfElmts	s
	)

Componentwise exponentiation of an array of ciphertext.

Definition at line 115 of file ciphergroup.cpp.

{
        return ArrayOfCiphers(grp->exponentiation(c.getUarray(),s),
                              grp->exponentiation(c.getVarray(),s));
}

CipherText CipherGroup::expProduct	(	ArrayOfCiphers	c,
		arithm::ArrayOfElmts	s
	)

Componentwise call to Group::expProduct().

Definition at line 123 of file ciphergroup.cpp.

{
        return CipherText(grp->expProduct(c.getUarray(),s),
                          grp->expProduct(c.getVarray(),s));
}

ArrayOfCiphers CipherGroup::getArrayOfCiphers ( verifierUtils::ByteTree * bt )

Returns an ArrayOfCiphers from this group built from a bytetree.

Definition at line 38 of file ciphergroup.cpp.

{
        return ArrayOfCiphers(bt,*this);
}

CipherText CipherGroup::getCipherText ( verifierUtils::ByteTree * bt )

Returns a CipherText from this group built from a bytetree.

Definition at line 32 of file ciphergroup.cpp.

{
        return CipherText(bt,*this);
}

arithm::Group * CipherGroup::getGrp ( )

Returns the group in which the computations are made.

Definition at line 26 of file ciphergroup.cpp.

{
        return grp;
}

CipherText CipherGroup::multiplication	(	CipherText	c1,
		CipherText	c2
	)

Componentwise multiplication of a ciphertext.

Definition at line 108 of file ciphergroup.cpp.

{
        return CipherText(grp->multiplication(c1.getU(),c2.getU()),
                          grp->multiplication(c1.getV(),c2.getV()));
}

arithm::Elmt CipherGroup::pdec	(	arithm::Elmt	xl,
		CipherText	uv
	)

Let uv be $(u,v)$ . Then returns $PDec_{x_l}(u,v) = u^{x_l}$ .

Definition at line 66 of file ciphergroup.cpp.

{
        return grp->exponentiation(uv.getU(),xl);
}

arithm::ArrayOfElmts CipherGroup::pdec	(	arithm::Elmt	xl,
		ArrayOfCiphers	uv
	)

Applies pdec component-wise on an array of cipher text using a fixed public key.

Definition at line 72 of file ciphergroup.cpp.

{
        arithm::ArrayOfElmts result;
        for (unsigned int i=0; i<uv.size(); i++)
                result.addElmt(pdec(xl, uv.getCipherText(i)));
        return result;
}

arithm::Elmt CipherGroup::tdec	(	CipherText	uv,
		arithm::Elmt	f
	)

Let uv be $(u,v)$ . The returns $TDec((u,v),f) = v f^{-1}$ .

Definition at line 81 of file ciphergroup.cpp.

{
        return grp->multiplication(uv.getV(),grp->multInverse(f));
}

arithm::ArrayOfElmts CipherGroup::tdec	(	ArrayOfCiphers	uv,
		arithm::ArrayOfElmts	f
	)

Applies tdec component-wise on an array of cipher texts and an array of decryption factors (i.e. group elements).

Definition at line 87 of file ciphergroup.cpp.

{
        arithm::ArrayOfElmts result;
        for (unsigned int i=0; i<uv.size(); i++)
                result.addElmt(tdec(uv.getCipherText(i),f.getElmt(i)));
        return result;
}

Member Data Documentation

arithm::Group* elGamal::CipherGroup::grp

private

The group in which computations are made.

Definition at line 34 of file ciphergroup.hpp.

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

elgamal/ciphergroup.hpp
elgamal/ciphergroup.cpp

Public Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation