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/*
* XMSS WOTS Public Key
* A Winternitz One Time Signature public key for use with Extended Hash-Based
* Signatures.
*
* (C) 2016 Matthias Gierlings
*
* Botan is released under the Simplified BSD License (see license.txt)
**/
#include <botan/xmss_wots_publickey.h>
namespace Botan {
void
XMSS_WOTS_PublicKey::chain(secure_vector<byte>& result,
size_t start_idx,
size_t steps,
XMSS_Address& adrs,
const secure_vector<byte>& seed)
{
for(size_t i = start_idx;
i < (start_idx + steps) && i < m_wots_params.wots_parameter();
i++)
{
adrs.set_hash_address(i);
//Calculate tmp XOR bitmask
adrs.set_key_mask_mode(XMSS_Address::Key_Mask::Mask_Mode);
xor_buf(result, m_hash.prf(seed, adrs.bytes()), result.size());
// Calculate key
adrs.set_key_mask_mode(XMSS_Address::Key_Mask::Key_Mode);
//Calculate f(key, tmp XOR bitmask)
m_hash.f(result, m_hash.prf(seed, adrs.bytes()), result);
}
}
wots_keysig_t
XMSS_WOTS_PublicKey::pub_key_from_signature(const secure_vector<byte>& msg,
const wots_keysig_t& sig,
XMSS_Address& adrs,
const secure_vector<byte>& seed)
{
secure_vector<byte> msg_digest
{
m_wots_params.base_w(msg, m_wots_params.len_1())
};
m_wots_params.append_checksum(msg_digest);
wots_keysig_t result(sig);
for(size_t i = 0; i < m_wots_params.len(); i++)
{
adrs.set_chain_address(i);
chain(result[i],
msg_digest[i],
m_wots_params.wots_parameter() - 1 - msg_digest[i],
adrs,
seed);
}
return result;
}
}
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