dmcfe.h File Reference

Decentralized multi-client inner-product scheme based on the paper "Decentralized Multi-Client Functional Encryption for Inner Product" by Chotard, Dufour Sans, Gay, Phan, and Pointcheval. More...

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Data Structures
struct	cfe_dmcfe_client

Typedefs
typedef struct cfe_dmcfe_client	cfe_dmcfe_client

Functions
void	cfe_dmcfe_client_init (cfe_dmcfe_client *c, size_t idx)
void	cfe_dmcfe_client_free (cfe_dmcfe_client *c)
void	cfe_dmcfe_set_share (cfe_dmcfe_client *c, ECP_BN254 *pub_keys, size_t num_clients)
void	cfe_dmcfe_encrypt (ECP_BN254 *cipher, cfe_dmcfe_client *c, mpz_t x, char *label, size_t label_len)
void	cfe_dmcfe_fe_key_part_init (cfe_vec_G2 *fe_key_part)
void	cfe_dmcfe_derive_fe_key_part (cfe_vec_G2 *fe_key_part, cfe_dmcfe_client *c, cfe_vec *y)
cfe_error	cfe_dmcfe_decrypt (mpz_t res, ECP_BN254 *ciphers, cfe_vec_G2 *key_shares, char *label, size_t label_len, cfe_vec *y, mpz_t bound)

Detailed Description

Decentralized multi-client inner-product scheme based on the paper "Decentralized Multi-Client Functional Encryption for Inner Product" by Chotard, Dufour Sans, Gay, Phan, and Pointcheval.

Typedef Documentation

cfe_dmcfe_client

typedef struct cfe_dmcfe_client cfe_dmcfe_client

cfe_dmcfe_client represents a client in a decentralized multi-client scheme.

Function Documentation

cfe_dmcfe_client_init()

void cfe_dmcfe_client_init	(	cfe_dmcfe_client *	c,
		size_t	idx
	)

Configures a new client for the dmcfe scheme.

Parameters

c	A pointer to an uninitialized struct representing the scheme
idx	Identification value of the client; it is assumed that if there are n clients, their identifications are from [0,n)

cfe_dmcfe_client_free()

void cfe_dmcfe_client_free

(

cfe_dmcfe_client *

c

)

Frees the memory occupied by the struct members. It does not free the memory occupied by the struct itself.

Parameters

c	A pointer to an instance of the scheme (initialized cfe_dmcfe_client struct)

cfe_dmcfe_set_share()

void cfe_dmcfe_set_share	(	cfe_dmcfe_client *	c,
		ECP_BN254 *	pub_keys,
		size_t	num_clients
	)

Sets a secret key share for the client based on the public keys of all the participant. Note that the function assumes that if there are n clients, their identifications are from [0,n).

Parameters

c	A pointer to an initialized struct representing the scheme
pub_keys	An array of public keys
num_clients	Number of clients

cfe_dmcfe_encrypt()

void cfe_dmcfe_encrypt	(	ECP_BN254 *	cipher,
		cfe_dmcfe_client *	c,
		mpz_t	x,
		char *	label,
		size_t	label_len
	)

Client c encrypts input value x, a coordinate of a vector. All clients should use the same label to encrypt a vector.

Parameters

cipher	A pointer to ECP_BN254 struct (the resulting ciphertext will be stored here)
c	A pointer to an instance of the scheme (initialized cfe_dmcfe_client
x	The input value
label	A string label of the encrypted vector
label_len	The length of the label to prevent non NULL terminated strings struct)

cfe_dmcfe_fe_key_part_init()

void cfe_dmcfe_fe_key_part_init

(

cfe_vec_G2 *

fe_key_part

)

Configures a new functional encryption key share for the dmcfe scheme.

Parameters

fe_key_part

A pointer to an uninitialized cfe_vec_G2 vec representing the share

cfe_dmcfe_derive_fe_key_part()

void cfe_dmcfe_derive_fe_key_part	(	cfe_vec_G2 *	fe_key_part,
		cfe_dmcfe_client *	c,
		cfe_vec *	y
	)

Sets a part of a functional encryption key needed for the decryption of an inner product of encrypted vector and y.

Parameters

fe_key_part	A pointer to initialized cfe_vec_G2 (the key share will be save here)
c	A pointer to an initialized struct representing the scheme
y	A pointer to the inner-product vector

cfe_dmcfe_decrypt()

cfe_error cfe_dmcfe_decrypt	(	mpz_t	res,
		ECP_BN254 *	ciphers,
		cfe_vec_G2 *	key_shares,
		char *	label,
		size_t	label_len,
		cfe_vec *	y,
		mpz_t	bound
	)

Accepts an array of ciphers, i.e. the encrypted vector, an array of key shares for the inner-product, a plaintext vector y, and a bound on the inputs of the encrypted and inner-product vector. The bound is used to improve the computation of the discrete logarithm needed for the decryption. It calculates the inner product of x and y. If decryption failed, an error is returned.

Parameters

res	The result of the decryption (the value will be stored here)
ciphers	An array of the encrypted coordinates of the vector
key_shares	An array of the decryption key shares
label	A string label of the encrypted value
label_len	The length of the label to prevent non NULL terminated strings
y	A pointer to the inner-product vector
bound	A bound on all the values of the encrypted vector and inner-product vector

Returns

Error code