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/**
* XMSS WOTS Parameters
* Descibes a signature method for XMSS Winternitz One Time Signatures,
* as defined in:
* [1] XMSS: Extended Hash-Based Signatures,
* draft-itrf-cfrg-xmss-hash-based-signatures-06
* Release: July 2016.
* https://datatracker.ietf.org/doc/
* draft-irtf-cfrg-xmss-hash-based-signatures/?include_text=1
*
* (C) 2016 Matthias Gierlings
*
* Botan is released under the Simplified BSD License (see license.txt)
**/
#include <botan/xmss_wots_parameters.h>
namespace Botan {
const std::map<std::string, XMSS_WOTS_Parameters::ots_algorithm_t>
XMSS_WOTS_Parameters::m_oid_name_lut =
{
{ "WOTSP_SHA2-256_W16", WOTSP_SHA2_256_W16 },
{ "WOTSP_SHA2-512_W16", WOTSP_SHA2_512_W16 }
};
XMSS_WOTS_Parameters::XMSS_WOTS_Parameters(const std::string& algo_name)
: XMSS_WOTS_Parameters(m_oid_name_lut.at(algo_name))
{}
XMSS_WOTS_Parameters::XMSS_WOTS_Parameters(ots_algorithm_t oid)
: m_oid(oid)
{
switch(oid)
{
case WOTSP_SHA2_256_W16:
m_element_size = 32;
m_w = 16;
m_len = 67;
m_name = "WOTSP_SHA2-256_W16";
m_hash_name = "SHA-256";
m_strength = 256;
break;
case WOTSP_SHA2_512_W16:
m_element_size = 64;
m_w = 16;
m_len = 131;
m_name = "WOTSP_SHA2-512_W16";
m_hash_name = "SHA-512";
m_strength = 512;
break;
// FIXME: Uncomment once SHAKE128/256 implementation is available in Botan.
// case WOTSP_SHAKE128_W16:
// m_element_size = 32;
// m_w = 16;
// m_len = 67;
// m_name = "WOTSP_SHAKE128_W16";
// m_hash_name = "<MISSING>";
// m_strength = 256;
// break;
// case WOTSP_SHAKE256_W16:
// m_element_size = 64;
// m_w = 16;
// m_len = 131;
// m_name = "WOTSP_SHAKE256_W16";
// m_hash_name = "<MISSING>";
// m_strength = 512;
// break;
default:
throw Unsupported_Argument(
"Algorithm id does not match any XMSS WOTS algorithm id.");
break;
}
m_w == 16 ? m_lg_w = 4 : m_lg_w = 2;
m_len_1 = static_cast<size_t>(ceil((8 * element_size()) / m_lg_w));
m_len_2 = static_cast<size_t>(
floor(log2(m_len_1 * (wots_parameter() - 1)) / m_lg_w) + 1);
BOTAN_ASSERT(m_len == m_len_1 + m_len_2, "Invalid XMSS WOTS parameter "
"\"len\" detedted.");
}
secure_vector<byte>
XMSS_WOTS_Parameters::base_w(const secure_vector<byte>& msg, size_t out_size) const
{
secure_vector<byte> result;
size_t in = 0;
size_t total = 0;
size_t bits = 0;
for(size_t i = 0; i < out_size; i++)
{
if(bits == 0)
{
total = msg[in];
in++;
bits += 8;
}
bits -= m_lg_w;
result.push_back(static_cast<byte>((total >> bits) & (m_w - 1)));
}
return result;
}
secure_vector<byte>
XMSS_WOTS_Parameters::base_w(size_t value) const
{
value <<= (8 - ((m_len_2 * m_lg_w) % 8));
size_t len_2_bytes = static_cast<size_t>(
ceil(static_cast<float>(m_len_2 * m_lg_w) / 8.f));
secure_vector<byte> result;
XMSS_Tools::get().concat(result, value, len_2_bytes);
return base_w(result, m_len_2);
}
void
XMSS_WOTS_Parameters::append_checksum(secure_vector<byte>& data)
{
size_t csum = 0;
for(size_t i = 0; i < data.size(); i++)
{
csum += wots_parameter() - 1 - data[i];
}
secure_vector<byte> csum_bytes = base_w(csum);
std::move(csum_bytes.begin(), csum_bytes.end(), std::back_inserter(data));
}
}
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