The HSS-LMS parameters. More...

#include <hss.h>

Classes
class	LMS_LMOTS_Params_Pair
	Represents a pair of LMS and LMOTS parameters associated with one LMS tree layer. More...

Public Member Functions
	HSS_LMS_Params (std::string_view algo_params)
	Construct the HSS-LMS parameters form an algorithm parameter string.

	HSS_LMS_Params (std::vector< LMS_LMOTS_Params_Pair > lm_lmots_params)
	Construct the HSS-LMS parameters from a vector LMS and LM-OTS parameters.

HSS_Level	L () const
	Returns the number of layers the HSS tree has.

HSS_Sig_Idx	max_sig_count () const
	The maximal number of signatures allowed for these HSS parameters.

const LMS_LMOTS_Params_Pair &	params_at_level (HSS_Level level) const
	Returns the LMS an LM-OTS parameters at the specified `level` of the HSS tree.

Detailed Description

The HSS-LMS parameters.

See RFC 8554 Section 6.

Definition at line 40 of file hss.h.

Constructor & Destructor Documentation

◆ HSS_LMS_Params() [1/2]

Botan::HSS_LMS_Params::HSS_LMS_Params ( std::vector< LMS_LMOTS_Params_Pair > lm_lmots_params )

explicit

Construct the HSS-LMS parameters from a vector LMS and LM-OTS parameters.

Definition at line 77 of file hss.cpp.

                                                                               :
      m_lms_lmots_params(std::move(lm_lmots_params)), m_max_sig_count(calc_max_sig_count()) {
   BOTAN_ARG_CHECK(!m_lms_lmots_params.empty() && m_lms_lmots_params.size() <= HSS_MAX_LEVELS,
                   "Invalid number of levels");
}

References BOTAN_ARG_CHECK.

◆ HSS_LMS_Params() [2/2]

Botan::HSS_LMS_Params::HSS_LMS_Params ( std::string_view algo_params )

explicit

Construct the HSS-LMS parameters form an algorithm parameter string.

The HSS/LMS instance to use for creating new keys is defined using an algorithm parameter string, i.e. to define which hash function (hash), LMS tree hights (h) and OTS Winternitz coefficient widths (w) to use. The syntax is the following:

HSS-LMS(<hash>,HW(<h>,<w>),HW(<h>,<w>),...)

e.g. 'HSS-LMS(SHA-256,HW(5,1),HW(5,1))' to use SHA-256 in a two-layer HSS instance with a LMS tree height 5 and w=1. The following parameters are allowed (which are specified in RFC 8554 and draft-fluhrer-lms-more-parm-sets-11):

hash: 'SHA-256', 'Truncated(SHA-256,192)', 'SHAKE-256(256)', SHAKE-256(192) h: '5', '10', '15', '20', '25' w: '1', '2', '4', '8'

Note: The selected hash function is also used for seed derivation.

Definition at line 83 of file hss.cpp.

                                                         {
   SCAN_Name scan(fmt("HSS-LMS({})", algo_params));
 
   BOTAN_ARG_CHECK(scan.arg_count() >= 2 && scan.arg_count() <= HSS_MAX_LEVELS + 1, "Invalid number of arguments");
   std::string hash = scan.arg(0);
   BOTAN_ARG_CHECK(is_supported_hash_function(hash), "Supported HSS-LMS hash function");
 
   for(size_t i = 1; i < scan.arg_count(); ++i) {
      SCAN_Name scan_layer(scan.arg(i));
      BOTAN_ARG_CHECK(scan_layer.algo_name() == "HW", "Invalid name for layer parameters");
      BOTAN_ARG_CHECK(scan_layer.arg_count() == 2, "Invalid number of layer parameters");
      const auto h =
         checked_cast_to_or_throw<uint8_t, Invalid_Argument>(scan_layer.arg_as_integer(0), "Invalid tree height");
      const auto w = checked_cast_to_or_throw<uint8_t, Invalid_Argument>(scan_layer.arg_as_integer(1),
                                                                         "Invalid Winternitz parameter");
      m_lms_lmots_params.push_back({LMS_Params::create_or_throw(hash, h), LMOTS_Params::create_or_throw(hash, w)});
   }
   m_max_sig_count = calc_max_sig_count();
}