normal_double_constant.h File Reference

Normal constant time sampler based on double sampling. More...

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Data Structures
struct	cfe_normal_double_constant

Typedefs
typedef struct cfe_normal_double_constant	cfe_normal_double_constant

Functions
void	cfe_normal_double_constant_init (cfe_normal_double_constant *s, mpz_t k)
void	cfe_normal_double_constant_free (cfe_normal_double_constant *s)
void	cfe_normal_double_constant_sample (mpz_t res, cfe_normal_double_constant *s)
void	cfe_normal_double_constant_sample_vec (cfe_vec *res, cfe_normal_double_constant *s)
void	cfe_normal_double_constant_sample_mat (cfe_mat *res, cfe_normal_double_constant *s)

Detailed Description

Normal constant time sampler based on double sampling.

Typedef Documentation

cfe_normal_double_constant

typedef struct cfe_normal_double_constant cfe_normal_double_constant

cfe_normal_double_constant samples random values from the normal (Gaussian) probability distribution, centered on 0. This sampler works in a way that it first samples from a cfe_normal_cdt - normal distribution with fixed sigma - and then using another sampling from uniform distribution creates a candidate for the output, which is accepted or rejected with certain probability. The sampler algorithm is constant time in the sense that the sampled value is independent of the time needed. The implementation is based on paper: "FACCT: FAst, Compact, and Constant-Time Discrete Gaussian Sampler over Integers" by R. K. Zhao, R. Steinfeld, and A. Sakzad, see https://eprint.iacr.org/2018/1234.pdf. See the above paper for the argumentation of the choice of parameters and proof of precision and security.

Function Documentation

cfe_normal_double_constant_init()

void cfe_normal_double_constant_init	(	cfe_normal_double_constant *	s,
		mpz_t	k
	)

Initializes an instance of cfe_normal_double_constant sampler. It assumes mean = 0. Parameter k needs to be given, such that sigma = k * sqrt(1/(2ln(2))).

Parameters

s	A pointer to an uninitialized struct representing the sampler
k	The value determining sigma = k * sqrt(1/(2ln(2)))

cfe_normal_double_constant_free()

void cfe_normal_double_constant_free

(

cfe_normal_double_constant *

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 sampler (initialized cfe_normal_double_constant struct)

cfe_normal_double_constant_sample()

void cfe_normal_double_constant_sample	(	mpz_t	res,
		cfe_normal_double_constant *	s
	)

Samples according to discrete Gaussian distribution using cfe_normal_double_constant.

Parameters

res	The sampling value (result value will be stored here)
s	A pointer to an instance of the sampler (initialized cfe_normal_double_constant struct)

cfe_normal_double_constant_sample_vec()

void cfe_normal_double_constant_sample_vec	(	cfe_vec *	res,
		cfe_normal_double_constant *	s
	)

Sets the elements of the vector to random numbers with the cfe_normal_double_constant sampler.

cfe_normal_double_constant_sample_mat()

void cfe_normal_double_constant_sample_mat	(	cfe_mat *	res,
		cfe_normal_double_constant *	s
	)

Sets the elements of a matrix to random numbers with the cfe_normal_double_constant sampler.