ddh.h File Reference

DDH scheme. More...

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Data Structures
struct	cfe_ddh

Typedefs
typedef struct cfe_ddh	cfe_ddh

Functions
cfe_error	cfe_ddh_init (cfe_ddh *s, size_t l, size_t modulus_len, mpz_t bound)
cfe_error	cfe_ddh_precomp_init (cfe_ddh *s, size_t l, size_t modulus_len, mpz_t bound)
void	cfe_ddh_free (cfe_ddh *s)
void	cfe_ddh_copy (cfe_ddh *res, cfe_ddh *s)
void	cfe_ddh_master_keys_init (cfe_vec *msk, cfe_vec *mpk, cfe_ddh *s)
void	cfe_ddh_ciphertext_init (cfe_vec *ciphertext, cfe_ddh *s)
void	cfe_ddh_generate_master_keys (cfe_vec *msk, cfe_vec *mpk, cfe_ddh *s)
cfe_error	cfe_ddh_derive_fe_key (mpz_t res, cfe_ddh *s, cfe_vec *msk, cfe_vec *y)
cfe_error	cfe_ddh_encrypt (cfe_vec *ciphertext, cfe_ddh *s, cfe_vec *x, cfe_vec *mpk)
cfe_error	cfe_ddh_decrypt (mpz_t res, cfe_ddh *s, cfe_vec *ciphertext, mpz_t key, cfe_vec *y)

Detailed Description

DDH scheme.

Typedef Documentation

cfe_ddh

typedef struct cfe_ddh cfe_ddh

cfe_ddh represents a scheme instantiated from the DDH assumption.

Function Documentation

cfe_ddh_init()

cfe_error cfe_ddh_init	(	cfe_ddh *	s,
		size_t	l,
		size_t	modulus_len,
		mpz_t	bound
	)

Configures a new instance of the scheme. It returns an error in case the scheme could not be properly configured, or if precondition 2 * l * bound² is >= order of the cyclic group.

Parameters

s	A pointer to an uninitialized struct representing the scheme
l	The length of input vectors
modulus_len	The bit length of the modulus
bound	The bound by which coordinates of input vectors are bounded

Returns

Error code

cfe_ddh_precomp_init()

cfe_error cfe_ddh_precomp_init	(	cfe_ddh *	s,
		size_t	l,
		size_t	modulus_len,
		mpz_t	bound
	)

Configures a new instance of the scheme based on precomputed prime numbers and generators. It returns an error in case the scheme could not be properly configured, or if precondition 2 * l * bound² is >= order of the cyclic group.

Parameters

s	A pointer to an uninitialized struct representing the scheme
l	The length of input vectors
modulus_len	The bit length of the modulus
bound	The bound by which coordinates of input vectors are bounded

Returns

Error code

cfe_ddh_free()

void cfe_ddh_free

(

cfe_ddh *

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_ddh struct)

cfe_ddh_copy()

void cfe_ddh_copy	(	cfe_ddh *	res,
		cfe_ddh *	s
	)

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

Parameters

res	A pointer to an uninitialized ddh struct
s	A pointer to an instance of the scheme (initialized cfe_ddh struct)

cfe_ddh_master_keys_init()

void cfe_ddh_master_keys_init	(	cfe_vec *	msk,
		cfe_vec *	mpk,
		cfe_ddh *	s
	)

Initializes the vectors which represent the master secret key and master public key.

Parameters

msk	A pointer to an uninitialized vector
mpk	A pointer to an uninitialized vector
s	A pointer to an instance of the scheme (initialized cfe_ddh struct)

cfe_ddh_ciphertext_init()

void cfe_ddh_ciphertext_init	(	cfe_vec *	ciphertext,
		cfe_ddh *	s
	)

Initializes the vector which represents the ciphertext.

Parameters

ciphertext	A pointer to an uninitialized vector
s	A pointer to an instance of the scheme (initialized cfe_ddh struct)

cfe_ddh_generate_master_keys()

void cfe_ddh_generate_master_keys	(	cfe_vec *	msk,
		cfe_vec *	mpk,
		cfe_ddh *	s
	)

Generates a pair of master secret key and master public key for the scheme. It returns an error in case master keys could not be generated.

Parameters

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

cfe_ddh_derive_fe_key()

cfe_error cfe_ddh_derive_fe_key	(	mpz_t	res,
		cfe_ddh *	s,
		cfe_vec *	msk,
		cfe_vec *	y
	)

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

Parameters

res	The derived key (the value will be stored here)
s	A pointer to an instance of the scheme (initialized cfe_ddh struct)
msk	A pointer to the master secret key
y	A pointer to the input vector

Returns

Error code

cfe_ddh_encrypt()

cfe_error cfe_ddh_encrypt	(	cfe_vec *	ciphertext,
		cfe_ddh *	s,
		cfe_vec *	x,
		cfe_vec *	mpk
	)

Encrypts input vector x with the provided master public key. It returns a ciphertext vector. If encryption failed, an error is returned.

Parameters

ciphertext	A pointer to a vector (the resulting ciphertext will be stored here)
s	A pointer to an instance of the scheme (initialized cfe_ddh struct)
x	A pointer to the input vector
mpk	A pointer to the master public key

Returns

Error code

cfe_ddh_decrypt()

cfe_error cfe_ddh_decrypt	(	mpz_t	res,
		cfe_ddh *	s,
		cfe_vec *	ciphertext,
		mpz_t	key,
		cfe_vec *	y
	)

Accepts the encrypted vector x, functional encryption key, and a plaintext vector y. It returns 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)
s	A pointer to an instance of the scheme (initialized cfe_ddh struct)
ciphertext	A pointer to the ciphertext vector
key	The functional encryption key
y	A pointer to the plaintext vector

Returns

Error code