damgard.h File Reference

Damgard scheme. More...

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Data Structures
struct	cfe_damgard
struct	cfe_damgard_sec_key
struct	cfe_damgard_fe_key

Typedefs
typedef struct cfe_damgard	cfe_damgard
typedef struct cfe_damgard_sec_key	cfe_damgard_sec_key
typedef struct cfe_damgard_fe_key	cfe_damgard_fe_key

Functions
cfe_error	cfe_damgard_init (cfe_damgard *s, size_t l, size_t modulus_len, mpz_t bound)
cfe_error	cfe_damgard_precomp_init (cfe_damgard *s, size_t l, size_t modulus_len, mpz_t bound)
void	cfe_damgard_free (cfe_damgard *s)
void	cfe_damgard_copy (cfe_damgard *res, cfe_damgard *s)
void	cfe_damgard_sec_key_free (cfe_damgard_sec_key *key)
void	cfe_damgard_fe_key_free (cfe_damgard_fe_key *key)
void	cfe_damgard_sec_key_init (cfe_damgard_sec_key *msk, cfe_damgard *s)
void	cfe_damgard_pub_key_init (cfe_vec *mpk, cfe_damgard *s)
void	cfe_damgard_generate_master_keys (cfe_damgard_sec_key *msk, cfe_vec *mpk, cfe_damgard *s)
void	cfe_damgard_fe_key_init (cfe_damgard_fe_key *fe_key)
cfe_error	cfe_damgard_derive_fe_key (cfe_damgard_fe_key *fe_key, cfe_damgard *s, cfe_damgard_sec_key *msk, cfe_vec *y)
void	cfe_damgard_ciphertext_init (cfe_vec *ciphertext, cfe_damgard *s)
cfe_error	cfe_damgard_encrypt (cfe_vec *ciphertext, cfe_damgard *s, cfe_vec *x, cfe_vec *mpk)
cfe_error	cfe_damgard_decrypt (mpz_t res, cfe_damgard *s, cfe_vec *ciphertext, cfe_damgard_fe_key *key, cfe_vec *y)

Detailed Description

Damgard scheme.

Typedef Documentation

cfe_damgard

typedef struct cfe_damgard cfe_damgard

cfe_damgard represents a scheme instantiated from the DDH assumption.

cfe_damgard_sec_key

typedef struct cfe_damgard_sec_key cfe_damgard_sec_key

cfe_damgard_sec_key is a secret key for Damgard scheme.

cfe_damgard_fe_key

typedef struct cfe_damgard_fe_key cfe_damgard_fe_key

cfe_damgard_fe_key is a functional encryption key for Damgard scheme.

Function Documentation

cfe_damgard_init()

cfe_error cfe_damgard_init	(	cfe_damgard *	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_damgard_precomp_init()

cfe_error cfe_damgard_precomp_init	(	cfe_damgard *	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_damgard_free()

void cfe_damgard_free

(

cfe_damgard *

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_damgard struct)

cfe_damgard_copy()

void cfe_damgard_copy	(	cfe_damgard *	res,
		cfe_damgard *	s
	)

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

Parameters

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

cfe_damgard_sec_key_free()

void cfe_damgard_sec_key_free

(

cfe_damgard_sec_key *

key

)

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

Parameters

key	A pointer to an initialized cfe_damgard_sec_key struct

cfe_damgard_fe_key_free()

void cfe_damgard_fe_key_free

(

cfe_damgard_fe_key *

key

)

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

Parameters

key	A pointer to an initialized cfe_damgard_fe_key struct

cfe_damgard_sec_key_init()

void cfe_damgard_sec_key_init	(	cfe_damgard_sec_key *	msk,
		cfe_damgard *	s
	)

Initializes the struct which represents the master secret key.

Parameters

msk	A pointer to an uninitialized cfe_damgard_sec_key struct
s	A pointer to an instance of the scheme (initialized cfe_damgard struct)

cfe_damgard_pub_key_init()

void cfe_damgard_pub_key_init	(	cfe_vec *	mpk,
		cfe_damgard *	s
	)

Initializes the vector which represents the master public key.

Parameters

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

cfe_damgard_generate_master_keys()

void cfe_damgard_generate_master_keys	(	cfe_damgard_sec_key *	msk,
		cfe_vec *	mpk,
		cfe_damgard *	s
	)

Generates a master secret key and master public key for the scheme.

Parameters

msk	A pointer to a cfe_damgard_sec_key struct (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_damgard struct)

cfe_damgard_fe_key_init()

void cfe_damgard_fe_key_init

(

cfe_damgard_fe_key *

fe_key

)

Initializes the struct which represents the functional encryption key.

Parameters

fe_key

A pointer to an uninitialized cfe_damgard_fe_key struct

cfe_damgard_derive_fe_key()

cfe_error cfe_damgard_derive_fe_key	(	cfe_damgard_fe_key *	fe_key,
		cfe_damgard *	s,
		cfe_damgard_sec_key *	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

fe_key	A pointer to a cfe_damgard_fe_key struct (the functional encryption key will be stored here)
s	A pointer to an instance of the scheme (initialized cfe_damgard struct)
msk	A pointer to the master secret key
y	A pointer to the inner product vector

Returns

Error code

cfe_damgard_ciphertext_init()

void cfe_damgard_ciphertext_init	(	cfe_vec *	ciphertext,
		cfe_damgard *	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_damgard struct)

cfe_damgard_encrypt()

cfe_error cfe_damgard_encrypt	(	cfe_vec *	ciphertext,
		cfe_damgard *	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_damgard struct)
x	A pointer to the input vector
mpk	A pointer to the master public key

Returns

Error code

cfe_damgard_decrypt()

cfe_error cfe_damgard_decrypt	(	mpz_t	res,
		cfe_damgard *	s,
		cfe_vec *	ciphertext,
		cfe_damgard_fe_key *	key,
		cfe_vec *	y
	)

Accepts the encrypted vector, 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_damgard struct)
ciphertext	A pointer to the ciphertext vector
key	The functional encryption key
y	A pointer to the inner product vector

Returns

Error code