dgk.h File Reference

A library implementing the DGK crypto system with full decryption Thanks to Marina Blanton for sharing her Miracl DGK implementation from M. Blanton and P. Gasti, "Secure and efficient protocols for iris and fingerprint identification" (ESORICS’11) with us. We used it as a template for this GMP version. More...

#include <gmp.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include "powmod.h"

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Classes
struct	dgk_pubkey_t
struct	dgk_prvkey_t

Functions
void	dgk_keygen (unsigned int modulusbits, unsigned int lbits, dgk_pubkey_t **pub, dgk_prvkey_t **prv)
void	dgk_encrypt_fb (mpz_t res, dgk_pubkey_t *pub, mpz_t pt, gmp_randstate_t rnd)
void	dgk_encrypt_plain (mpz_t res, dgk_pubkey_t *pub, mpz_t pt, gmp_randstate_t rnd)
void	dgk_encrypt_crt (mpz_t res, dgk_pubkey_t *pub, dgk_prvkey_t *prv, mpz_t pt, gmp_randstate_t rnd)
void	dgk_decrypt (mpz_t res, dgk_pubkey_t *pub, dgk_prvkey_t *prv, mpz_t ct)
void	dgk_storekey (unsigned int modulusbits, unsigned int lbits, dgk_pubkey_t *pub, dgk_prvkey_t *prv)
void	dgk_readkey (unsigned int modulusbits, unsigned int lbits, dgk_pubkey_t **pub, dgk_prvkey_t **prv)
void	dgk_freepubkey (dgk_pubkey_t *pub)
void	dgk_freeprvkey (dgk_prvkey_t *prv)
void	dgk_complete_pubkey (unsigned int modulusbits, unsigned int lbits, dgk_pubkey_t **pub, mpz_t n, mpz_t g, mpz_t h)

Variables
mpz_t *	powtwo
mpz_t *	gvpvqp

Detailed Description

A library implementing the DGK crypto system with full decryption Thanks to Marina Blanton for sharing her Miracl DGK implementation from M. Blanton and P. Gasti, "Secure and efficient protocols for iris and fingerprint identification" (ESORICS’11) with us. We used it as a template for this GMP version.

Author

Daniel Demmler

Copyright

Copyright (C) 2015 EC SPRIDE - danie.nosp@m.l.de.nosp@m.mmler.nosp@m.@ec-.nosp@m.sprid.nosp@m.e.de

The implementation structure was inspired by libpailler - A library implementing the Paillier crypto system. (http://hms.isi.jhu.edu/acsc/libpaillier/)

Function Documentation

void dgk_complete_pubkey	(	unsigned int	modulusbits,
		unsigned int	lbits,
		dgk_pubkey_t **	pub,
		mpz_t	n,
		mpz_t	g,
		mpz_t	h
	)

create the full public key struct type given only n, g and h (e.g. after key exchange)

void dgk_decrypt	(	mpz_t	res,
		dgk_pubkey_t *	pub,
		dgk_prvkey_t *	prv,
		mpz_t	ct
	)

use CRT and double base combined - unfortunately not efficient due to different sized exponents, therefore deactivated DGK decryption

void dgk_encrypt_crt	(	mpz_t	res,
		dgk_pubkey_t *	pub,
		dgk_prvkey_t *	prv,
		mpz_t	pt,
		gmp_randstate_t	rnd
	)

encrypt using CRT if we have the private key for efficiency

void dgk_encrypt_fb	(	mpz_t	res,
		dgk_pubkey_t *	pub,
		mpz_t	pt,
		gmp_randstate_t	rnd
	)

encrypt with public key only and double-base encryption - unfortunately not efficient due to different sized exponents, therefore deactivated encrypt with public key only, fixed-base encryption (must be initialized before first use!)

void dgk_encrypt_plain	(	mpz_t	res,
		dgk_pubkey_t *	pub,
		mpz_t	pt,
		gmp_randstate_t	rnd
	)

encrypt with public key only, no further optimization (slower than fixed-base encryption)

void dgk_keygen	(	unsigned int	modulusbits,
		unsigned int	lbits,
		dgk_pubkey_t **	pub,
		dgk_prvkey_t **	prv
	)

create a DGK key pair. This will take some time, depending on the size (up to several minutes!) modulusbits is the size of the modulus n, e.g. 1024 or 2048 bit lbits is equal to the share length, e.g. 16 or 32 bit (We use 2*lbits+2 internally) the parameter t is internally fixed to 160, as recommended in the paper

void dgk_readkey	(	unsigned int	modulusbits,
		unsigned int	lbits,
		dgk_pubkey_t **	pub,
		dgk_prvkey_t **	prv
	)

reads a previously stored key pair from disc

void dgk_storekey	(	unsigned int	modulusbits,
		unsigned int	lbits,
		dgk_pubkey_t *	pub,
		dgk_prvkey_t *	prv
	)

stores a generated key pair to disc