Threshold Secret Sharing
========================================
.. versionadded:: 1.9.1
Threshold secret sharing allows splitting a secret into ``N`` shares such that
``M`` (for specified ``M`` <= ``N``) is sufficient to recover the secret, but an
attacker with ``M - 1`` shares cannot derive any information about the secret.
The implementation in Botan follows an expired Internet draft
"draft-mcgrew-tss-03". Several other implementations of this TSS format exist.
.. cpp:class:: RTSS_Share
.. cpp:function:: static std::vector<RTSS_Share> split(uint8_t M, uint8_t N, \
const uint8_t secret[], uint16_t secret_len, \
const std::vector<uint8_t>& identifier, \
const std::string& hash_fn, \
RandomNumberGenerator& rng)
Split a secret. The identifier is an optional key identifier which may be
up to 16 bytes long. Shorter identifiers are padded with zeros.
The hash function must be either "SHA-1", "SHA-256", or "None" to disable
the checksum.
This will return a vector of length ``N``, any ``M`` of these shares is
sufficient to reconstruct the data.
.. cpp:function:: static secure_vector<uint8_t> reconstruct(const std::vector<RTSS_Share>& shares)
Given a sufficient number of shares, reconstruct a secret.
.. cpp:function:: RTSS_Share(const uint8_t data[], size_t len)
Read a TSS share as a sequence of bytes.
.. cpp:function:: const secure_vector<uint8>& data() const
Return the data of this share.
.. cpp:function:: uint8_t share_id() const
Return the share ID which will be in the range 1...255