sgp.h File Reference

SGP scheme. More...

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Data Structures
struct	cfe_sgp
struct	cfe_sgp_sec_key
struct	cfe_sgp_cipher

Typedefs
typedef struct cfe_sgp	cfe_sgp
typedef struct cfe_sgp_sec_key	cfe_sgp_sec_key
typedef struct cfe_sgp_cipher	cfe_sgp_cipher

Functions
cfe_error	cfe_sgp_init (cfe_sgp *s, size_t l, mpz_t bound)
void	cfe_sgp_free (cfe_sgp *s)
void	cfe_sgp_sec_key_init (cfe_sgp_sec_key *msk, cfe_sgp *sgp)
void	cfe_sgp_sec_key_free (cfe_sgp_sec_key *msk)
void	cfe_sgp_generate_sec_key (cfe_sgp_sec_key *msk, cfe_sgp *s)
cfe_error	cfe_sgp_derive_fe_key (ECP2_BN254 *key, cfe_sgp *sgp, cfe_sgp_sec_key *msk, cfe_mat *f)
void	cfe_sgp_cipher_init (cfe_sgp_cipher *cipher, cfe_sgp *s)
void	cfe_sgp_cipher_free (cfe_sgp_cipher *cipher)
cfe_error	cfe_sgp_encrypt (cfe_sgp_cipher *cipher, cfe_sgp *s, cfe_vec *x, cfe_vec *y, cfe_sgp_sec_key *msk)
cfe_error	cfe_sgp_decrypt (mpz_t res, cfe_sgp *s, cfe_sgp_cipher *cipher, ECP2_BN254 *key, cfe_mat *f)

Detailed Description

SGP scheme.

Typedef Documentation

cfe_sgp

typedef struct cfe_sgp cfe_sgp

cfe_sgp represents a scheme for quadratic multi-variate polynomials based on Sans, Gay and Pointcheval: "Reading in the Dark: Classifying Encrypted Digits with Functional Encryption", see https://eprint.iacr.org/2018/206.pdf.

cfe_sgp_sec_key

typedef struct cfe_sgp_sec_key cfe_sgp_sec_key

cfe_sgp_sec_key represents a secret key for SGP scheme.

cfe_sgp_cipher

typedef struct cfe_sgp_cipher cfe_sgp_cipher

cfe_sgp_sec_key represents a ciphertext in SGP scheme.

Function Documentation

cfe_sgp_init()

cfe_error cfe_sgp_init	(	cfe_sgp *	s,
		size_t	l,
		mpz_t	bound
	)

Configures a new instance of the scheme.

Parameters

s	A pointer to an uninitialized struct representing the scheme
l	The length of input vectors
bound	The bound by which coordinates of the encryption vectors and matrix for quadratic polynomial are bounded

Returns

Error code

cfe_sgp_free()

void cfe_sgp_free

(

cfe_sgp *

s

)

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

Parameters

s	A pointer to an instance of the scheme (initialized cfe_sgp struct)

cfe_sgp_sec_key_init()

void cfe_sgp_sec_key_init	(	cfe_sgp_sec_key *	msk,
		cfe_sgp *	sgp
	)

Initializes the struct which represents the master secret key.

Parameters

msk	A pointer to an uninitialized secret key
sgp	A pointer to an instance of the scheme (initialized cfe_sgp struct)

cfe_sgp_sec_key_free()

void cfe_sgp_sec_key_free

(

cfe_sgp_sec_key *

msk

)

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

Parameters

msk	A pointer to an instance of the secret key (initialized cfe_sgp_sec_key struct)

cfe_sgp_generate_sec_key()

void cfe_sgp_generate_sec_key	(	cfe_sgp_sec_key *	msk,
		cfe_sgp *	s
	)

Generates a private secret key for the scheme.

Parameters

msk	A pointer to a secret key (master secret key will be stored here)
s	A pointer to an instance of the scheme (initialized cfe_sgp struct)

Returns

Error code

cfe_sgp_derive_fe_key()

cfe_error cfe_sgp_derive_fe_key	(	ECP2_BN254 *	key,
		cfe_sgp *	sgp,
		cfe_sgp_sec_key *	msk,
		cfe_mat *	f
	)

Takes master secret key and a matrix, and returns the corresponding functional encryption key.

Parameters

key	A pointer to a ECP2_BN254 struct (the functional encryption key will be stored here)
sgp	A pointer to an instance of the scheme (initialized cfe_sgp struct)
msk	A pointer to the master secret key
f	A pointer to the matrix for the quadratic polynomial

Returns

Error code

cfe_sgp_cipher_init()

void cfe_sgp_cipher_init	(	cfe_sgp_cipher *	cipher,
		cfe_sgp *	s
	)

Initializes the struct which represents the ciphertext.

Parameters

cipher	A pointer to an uninitialized ciphertext struct
s	A pointer to an instance of the scheme (initialized cfe_sgp struct)

cfe_sgp_cipher_free()

void cfe_sgp_cipher_free

(

cfe_sgp_cipher *

cipher

)

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

Parameters

cipher

A pointer to an instance of the ciphertext (initialized cfe_sgp_cipher struct)

cfe_sgp_encrypt()

cfe_error cfe_sgp_encrypt	(	cfe_sgp_cipher *	cipher,
		cfe_sgp *	s,
		cfe_vec *	x,
		cfe_vec *	y,
		cfe_sgp_sec_key *	msk
	)

Encrypts input vectors x and y with the provided master secret key.

Parameters

cipher	A pointer to a vector (the resulting ciphertext will be stored here)
s	A pointer to an instance of the scheme (initialized cfe_sgp struct)
x	A pointer to the input vector
y	A pointer to the input vector
msk	A pointer to a master secret key.

Returns

Error code

cfe_sgp_decrypt()

cfe_error cfe_sgp_decrypt	(	mpz_t	res,
		cfe_sgp *	s,
		cfe_sgp_cipher *	cipher,
		ECP2_BN254 *	key,
		cfe_mat *	f
	)

Based on the encryption, functional encryption key, and a matrix, it returns the value of the quadratic polynomial. If decryption failed, an error is returned.

Parameters

res	The result of the decryption (the value will be stored here)
s	A pointer to an instance of the scheme (initialized cfe_sgp struct)
cipher	A pointer to the ciphertext
key	A pointer to the functional encryption key
f	A pointer to the matrix of the quadratic polynomial

Returns

Error code