ccf::crypto::sharing Namespace Reference

Classes
struct	Share

Typedefs
using	element = uint64_t

Functions
element	ct_reduce (element x)
void	sample_secret_and_shares (Share &raw_secret, const std::span< Share > &shares, size_t threshold)
void	recover_unauthenticated_secret (Share &raw_secret, const std::span< Share const > &shares, size_t threshold)

Variables
constexpr size_t	SHIFT_OFFSET = 31
constexpr element	prime

Typedef Documentation

element

typedef uint64_t ccf::crypto::sharing::element

Function Documentation

ct_reduce()

element ccf::crypto::sharing::ct_reduce

(

element

x

)

recover_unauthenticated_secret()

void ccf::crypto::sharing::recover_unauthenticated_secret	(	Share &	raw_secret,
		const std::span< Share const > &	shares,
		size_t	threshold
	)

Using shares, recover secret, without authentication.

Parameters

[out]	raw_secret	Recovered secret value.
[in]	shares	Shares of raw_secret.
	threshold	Number of shares necessary to recover the secret.

Note that shares passed in excess of the threshold are ignored, and that recovery does not authenticate the shares or the threshold.

Exceptions

std::invalid_argument

if the number of shares is insufficient, or if two shares have the same x coordinate.

sample_secret_and_shares()

void ccf::crypto::sharing::sample_secret_and_shares	(	Share &	raw_secret,
		const std::span< Share > &	shares,
		size_t	threshold
	)

Sample a secret into raw_secret, and split it into shares. Enforces 1 < threshold <= number of shares.

Parameters

[out]	raw_secret	Sampled secret value.
[out]	shares	Shares of raw_secret. Note that the size of the span determines the number of shares.
[in]	threshold	Number of shares necessary to recover the secret.

The secret is guaranteed to contain at least 256 bits of entropy. Note that is it not safe to use the secret as a key directly, and that a round of key derivation is necessary (Share::key()).

Variable Documentation

prime

constexpr element ccf::crypto::sharing::prime

constexpr

Initial value:

=
    (1UL << SHIFT_OFFSET) - 1UL

SHIFT_OFFSET

constexpr size_t ccf::crypto::sharing::SHIFT_OFFSET = 31

constexpr