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/*
* XMSS Signature Operation
* Signature generation operation for Extended Hash-Based Signatures (XMSS) as
* defined in:
*
* [1] XMSS: Extended Hash-Based Signatures,
* Request for Comments: 8391
* Release: May 2018.
*
* (C) 2016,2017,2018 Matthias Gierlings
*
* Botan is released under the Simplified BSD License (see license.txt)
**/
#include <botan/internal/xmss_signature_operation.h>
#include <botan/internal/xmss_tools.h>
namespace Botan {
XMSS_Signature_Operation::XMSS_Signature_Operation(
const XMSS_PrivateKey& private_key) :
m_priv_key(private_key),
m_xmss_params(private_key.xmss_oid()),
m_hash(private_key.xmss_hash_function()),
m_randomness(0),
m_leaf_idx(0),
m_is_initialized(false)
{}
XMSS_WOTS_PublicKey::TreeSignature
XMSS_Signature_Operation::generate_tree_signature(const secure_vector<uint8_t>& msg,
XMSS_PrivateKey& xmss_priv_key,
XMSS_Address& adrs)
{
wots_keysig_t auth_path = build_auth_path(xmss_priv_key, adrs);
adrs.set_type(XMSS_Address::Type::OTS_Hash_Address);
adrs.set_ots_address(m_leaf_idx);
wots_keysig_t sig_ots = xmss_priv_key.wots_private_key().sign(msg, adrs);
return XMSS_WOTS_PublicKey::TreeSignature(sig_ots, auth_path);
}
XMSS_Signature
XMSS_Signature_Operation::sign(const secure_vector<uint8_t>& msg_hash,
XMSS_PrivateKey& xmss_priv_key)
{
XMSS_Address adrs;
XMSS_Signature sig(m_leaf_idx,
m_randomness,
generate_tree_signature(msg_hash, xmss_priv_key,adrs));
return sig;
}
size_t XMSS_Signature_Operation::signature_length() const
{
return sizeof(uint64_t) + // size of leaf index
m_xmss_params.element_size() +
m_xmss_params.len() * m_xmss_params.element_size() +
m_xmss_params.tree_height() * m_xmss_params.element_size();
}
wots_keysig_t
XMSS_Signature_Operation::build_auth_path(XMSS_PrivateKey& priv_key,
XMSS_Address& adrs)
{
wots_keysig_t auth_path(m_xmss_params.tree_height());
adrs.set_type(XMSS_Address::Type::Hash_Tree_Address);
for(size_t j = 0; j < m_xmss_params.tree_height(); j++)
{
size_t k = (m_leaf_idx / (1ULL << j)) ^ 0x01;
auth_path[j] = priv_key.tree_hash(k * (1ULL << j), j, adrs);
}
return auth_path;
}
void XMSS_Signature_Operation::update(const uint8_t msg[], size_t msg_len)
{
initialize();
m_hash.h_msg_update(msg, msg_len);
}
secure_vector<uint8_t>
XMSS_Signature_Operation::sign(RandomNumberGenerator&)
{
initialize();
secure_vector<uint8_t> signature(sign(m_hash.h_msg_final(),
m_priv_key).bytes());
m_is_initialized = false;
return signature;
}
void XMSS_Signature_Operation::initialize()
{
// return if we already initialized and reserved a leaf index for signing.
if(m_is_initialized)
{ return; }
secure_vector<uint8_t> index_bytes;
// reserve leaf index so it can not be reused in by another signature
// operation using the same private key.
m_leaf_idx = static_cast<uint32_t>(m_priv_key.reserve_unused_leaf_index());
// write prefix for message hashing into buffer.
XMSS_Tools::concat(index_bytes, m_leaf_idx, 32);
m_randomness = m_hash.prf(m_priv_key.prf(), index_bytes);
index_bytes.clear();
XMSS_Tools::concat(index_bytes, m_leaf_idx,
m_priv_key.xmss_parameters().element_size());
m_hash.h_msg_init(m_randomness,
m_priv_key.root(),
index_bytes);
m_is_initialized = true;
}
}