// FH-Multi-IPE represents a Function Hiding Multi-client Inner Product Encryption scheme based on the paper by P. Datta, T. Okamoto, and J. Tomida: "Full-Hiding (Unbounded) Multi-Input Inner Product Functional Encryption from the 𝒌-Linear Assumption". It allows clients to encrypt vectors {x_1,...,x_m} and derive a secret key based on an inner product vectors {y_1,...,y_m} so that a decryptor can decrypt the sum of inner products <x_1,y_1> + ... + <x_m, y_m> without revealing vectors x_i or y_i. The scheme is slightly modified from the original one to achieve a better performance. The difference is in storing the secret master key as matrices B_hat, B_hat_star, instead of matrices of elliptic curve elements g_1^B_hat, g_2^B_hat_star. This replaces elliptic curves operations with matrix multiplications. More...

Data Structures
struct	cfe_fh_multi_ipe

struct	cfe_fh_multi_ipe_sec_key

Typedefs
typedef struct cfe_fh_multi_ipe	cfe_fh_multi_ipe

typedef struct cfe_fh_multi_ipe_sec_key	cfe_fh_multi_ipe_sec_key

Functions
cfe_error	cfe_fh_multi_ipe_init (cfe_fh_multi_ipe *c, size_t sec_level, size_t num_clients, size_t vec_len, mpz_t bound_x, mpz_t bound_y)

void	cfe_fh_multi_ipe_copy (cfe_fh_multi_ipe res, cfe_fh_multi_ipe c)

void	cfe_fh_multi_ipe_free (cfe_fh_multi_ipe *c)

void	cfe_fh_multi_ipe_master_key_init (cfe_fh_multi_ipe_sec_key sec_key, cfe_fh_multi_ipe c)

void	cfe_fh_multi_ipe_master_key_free (cfe_fh_multi_ipe_sec_key *sec_key)

cfe_error	cfe_fh_multi_ipe_generate_keys (cfe_fh_multi_ipe_sec_key sec_key, FP12_BN254 pub_key, cfe_fh_multi_ipe *c)

void	cfe_fh_multi_ipe_fe_key_init (cfe_mat_G2 fe_key, cfe_fh_multi_ipe c)

cfe_error	cfe_fh_multi_ipe_derive_fe_key (cfe_mat_G2 fe_key, cfe_mat y, cfe_fh_multi_ipe_sec_key sec_key, cfe_fh_multi_ipe c)

void	cfe_fh_multi_ipe_ciphertext_init (cfe_vec_G1 cipher, cfe_fh_multi_ipe c)

cfe_error	cfe_fh_multi_ipe_encrypt (cfe_vec_G1 cipher, cfe_vec x, cfe_mat part_sec_key, cfe_fh_multi_ipe c)

cfe_error	cfe_fh_multi_ipe_decrypt (mpz_t res, cfe_vec_G1 ciphers, cfe_mat_G2 fe_key, FP12_BN254 pub_key, cfe_fh_multi_ipe c)

Detailed Description

// FH-Multi-IPE represents a Function Hiding Multi-client Inner Product Encryption scheme based on the paper by P. Datta, T. Okamoto, and J. Tomida: "Full-Hiding (Unbounded) Multi-Input Inner Product Functional Encryption from the 𝒌-Linear Assumption". It allows clients to encrypt vectors {x_1,...,x_m} and derive a secret key based on an inner product vectors {y_1,...,y_m} so that a decryptor can decrypt the sum of inner products <x_1,y_1> + ... + <x_m, y_m> without revealing vectors x_i or y_i. The scheme is slightly modified from the original one to achieve a better performance. The difference is in storing the secret master key as matrices B_hat, B_hat_star, instead of matrices of elliptic curve elements g_1^B_hat, g_2^B_hat_star. This replaces elliptic curves operations with matrix multiplications.

Typedef Documentation

◆ cfe_fh_multi_ipe

typedef struct cfe_fh_multi_ipe cfe_fh_multi_ipe

cfe_fh_multi_ipe contains the shared choice for parameters on which the functionality of the scheme depend.

◆ cfe_fh_multi_ipe_sec_key

typedef struct cfe_fh_multi_ipe_sec_key cfe_fh_multi_ipe_sec_key

cfe_fh_multi_ipe_sec_key represents a master secret key in fh_multi_ipe scheme.

Function Documentation

◆ cfe_fh_multi_ipe_init()

cfe_error cfe_fh_multi_ipe_init	(	cfe_fh_multi_ipe *	c,
		size_t	sec_level,
		size_t	num_clients,
		size_t	vec_len,
		mpz_t	bound_x,
		mpz_t	bound_y
	)

Configures a new client for the fh_multi_ipe scheme. It returns an error if the bounds and length of vectors are too high.

Parameters

c	A pointer to an uninitialized struct representing the scheme
sec_level	The parameter defines the security assumption of the scheme, so called k-Lin assumption, where k is the specified sec_level
num_clients	Number of clients participating in the scheme
vec_len	Length of the vectors that each client will encrypt
bound_x	Bound on the inputs of the vectors that will be encrypted
bound_y	Bound on the inputs of the inner product vectors for which the functional keys will be generated.

Returns: Error code

◆ cfe_fh_multi_ipe_copy()

void cfe_fh_multi_ipe_copy	(	cfe_fh_multi_ipe *	res,
		cfe_fh_multi_ipe *	c
	)

Reconstructs the scheme with the same configuration parameters from an already existing fh_multi_ipe scheme instance.

Parameters

res	A pointer to an uninitialized cfe_fh_multi_ipe struct
c	A pointer to an instance of the scheme (initialized cfe_fh_multi_ipe struct)

◆ cfe_fh_multi_ipe_free()

void cfe_fh_multi_ipe_free ( cfe_fh_multi_ipe * 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_fh_multi_ipe struct)

◆ cfe_fh_multi_ipe_master_key_init()

void cfe_fh_multi_ipe_master_key_init	(	cfe_fh_multi_ipe_sec_key *	sec_key,
		cfe_fh_multi_ipe *	c
	)

Initializes the struct which represents the master secret key in fh_multi_ipe.

Parameters

sec_key	A pointer to an uninitialized cfe_fh_multi_ipe_sec_key struct
c	A pointer to an instance of the scheme (initialized cfe_fh_multi_ipe struct)

◆ cfe_fh_multi_ipe_master_key_free()

void cfe_fh_multi_ipe_master_key_free ( cfe_fh_multi_ipe_sec_key * sec_key )

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

Parameters

sec_key A pointer to an initialized cfe_fh_multi_ipe_sec_key struct

◆ cfe_fh_multi_ipe_generate_keys()

cfe_error cfe_fh_multi_ipe_generate_keys	(	cfe_fh_multi_ipe_sec_key *	sec_key,
		FP12_BN254 *	pub_key,
		cfe_fh_multi_ipe *	c
	)

Generates a master secret key and a public key for the scheme. It returns an error if generating one of the parts of the secret key failed.

Parameters

sec_key	A pointer to a cfe_fh_multi_ipe_sec_key struct (the master secret key will be stored here)
pub_key	A pointer to a FH12_BN256 struct (the public key will be stored here)
c	A pointer to an instance of the scheme (initialized cfe_fh_multi_ipe struct)

Returns: Error code

◆ cfe_fh_multi_ipe_fe_key_init()

void cfe_fh_multi_ipe_fe_key_init	(	cfe_mat_G2 *	fe_key,
		cfe_fh_multi_ipe *	c
	)

Initializes the struct which represents the functional encryption key in fh_multi_ipe.

Parameters

fe_key	A pointer to an uninitialized cfe_mat_G2 struct
c	A pointer to an instance of the scheme (initialized cfe_fh_multi_ipe struct)

◆ cfe_fh_multi_ipe_derive_fe_key()

cfe_error cfe_fh_multi_ipe_derive_fe_key	(	cfe_mat_G2 *	fe_key,
		cfe_mat *	y,
		cfe_fh_multi_ipe_sec_key *	sec_key,
		cfe_fh_multi_ipe *	c
	)

Takes a master secret key and input matrix y, and derives the functional encryption key. In case the key could not be derived, it returns an error.

Parameters

fe_key	A pointer to a cfe_mat_G2 struct (the functional encryption key will be stored here)
y	A pointer to the inner product matrix
sec_key	A pointer to the master secret key
c	A pointer to an instance of the scheme (initialized cfe_fh_multi_ipe struct)

Returns: Error code

◆ cfe_fh_multi_ipe_ciphertext_init()

void cfe_fh_multi_ipe_ciphertext_init	(	cfe_vec_G1 *	cipher,
		cfe_fh_multi_ipe *	c
	)

Initializes the struct which represents the ciphertext.

Parameters

cipher	A pointer to an uninitialized cfe_vec_G1 struct
c	A pointer to an instance of the scheme (initialized cfe_fh_multi_ipe struct)

◆ cfe_fh_multi_ipe_encrypt()

cfe_error cfe_fh_multi_ipe_encrypt	(	cfe_vec_G1 *	cipher,
		cfe_vec *	x,
		cfe_mat *	part_sec_key,
		cfe_fh_multi_ipe *	c
	)

The function is called by a client that encrypts input vector x with the provided part master secret key. It returns a ciphertext struct. If encryption failed, an error is returned.

Parameters

cipher	A pointer to an initialized cfe_vec_G1 struct (the resulting ciphertext will be stored here)
x	A pointer to the plaintext vector
part_sec_key	A pointer to a matrix representing a part of the master secret key (i-th client gets i-th matrix in array B_hat)
c	A pointer to an instance of the scheme (initialized cfe_fh_multi_ipe struct)

Returns: Error code

◆ cfe_fh_multi_ipe_decrypt()

cfe_error cfe_fh_multi_ipe_decrypt	(	mpz_t	res,
		cfe_vec_G1 *	ciphers,
		cfe_mat_G2 *	fe_key,
		FP12_BN254 *	pub_key,
		cfe_fh_multi_ipe *	c
	)

Accepts the encrypted vectors and functional encryption key. It returns the inner product of x and y, i.e. <x_1,y_1> + ... + <x_m, y_m> where x_i is i-th encrypted vector and y_i is i-th inner product vector (i-th row of 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 ciphertexts
fe_key	A pointer to the functional encryption key
pub_key	A pointer to the public key
c	A pointer to an instance of the scheme (initialized cfe_fh_multi_ipe struct)

Returns: Error code

Data Structures

Typedefs

Functions

Detailed Description

Typedef Documentation

◆ cfe_fh_multi_ipe

◆ cfe_fh_multi_ipe_sec_key

Function Documentation

◆ cfe_fh_multi_ipe_init()

◆ cfe_fh_multi_ipe_copy()

◆ cfe_fh_multi_ipe_free()

◆ cfe_fh_multi_ipe_master_key_init()

◆ cfe_fh_multi_ipe_master_key_free()

◆ cfe_fh_multi_ipe_generate_keys()

◆ cfe_fh_multi_ipe_fe_key_init()

◆ cfe_fh_multi_ipe_derive_fe_key()

◆ cfe_fh_multi_ipe_ciphertext_init()

◆ cfe_fh_multi_ipe_encrypt()

◆ cfe_fh_multi_ipe_decrypt()