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/*
* XMSS_PrivateKey.h
* (C) 2016 Matthias Gierlings
*
* Botan is released under the Simplified BSD License (see license.txt)
**/
#ifndef BOTAN_XMSS_PRIVATEKEY_H__
#define BOTAN_XMSS_PRIVATEKEY_H__
#include <cstddef>
#include <iterator>
#include <memory>
#include <botan/alg_id.h>
#include <botan/assert.h>
#include <botan/exceptn.h>
#include <botan/pk_keys.h>
#include <botan/rng.h>
#include <botan/types.h>
#include <botan/xmss_parameters.h>
#include <botan/xmss_publickey.h>
#include <botan/atomic.h>
#include <botan/xmss_common_ops.h>
#include <botan/xmss_wots_privatekey.h>
#include <botan/xmss_index_registry.h>
namespace Botan {
/**
* An XMSS: Extended Hash-Based Signature private key.
* The XMSS private key does not support the X509 and PKCS7 standard. Instead
* the raw format described in [1] is used.
*
* [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
**/
class BOTAN_DLL XMSS_PrivateKey : public virtual XMSS_PublicKey,
public XMSS_Common_Ops,
public virtual Private_Key
{
public:
/**
* Creates a new XMSS private key for the chosen XMSS signature method.
* New seeds for public/private key and pseudo random function input are
* generated using the provided RNG. The appropriate WOTS signature method
* will be automatically set based on the chosen XMSS signature method.
*
* @param xmss_algo_id Identifier for the selected XMSS signature method.
* @param rng A random number generator to use for key generation.
**/
XMSS_PrivateKey(XMSS_Parameters::xmss_algorithm_t xmss_algo_id,
RandomNumberGenerator& rng);
/**
* Creates an XMSS_PrivateKey from a byte sequence produced by
* raw_private_key().
*
* @param raw_key An XMSS private key serialized using raw_private_key().
**/
XMSS_PrivateKey(const secure_vector<uint8_t>& raw_key);
/**
* Creates a new XMSS private key for the chosen XMSS signature method
* using precomputed seeds for public/private keys and pseudo random
* function input. The appropriate WOTS signature method will be
* automatically set, based on the chosen XMSS signature method.
*
* @param xmss_algo_id Identifier for the selected XMSS signature method.
* @param idx_leaf Index of the next unused leaf.
* @param wots_priv_seed A seed to generate a Winternitz-One-Time-
* Signature private key from.
* @param prf a secret n-byte key sourced from a secure source
* of uniformly random data.
* @param root Root node of the binary hash tree.
* @param public_seed The public seed.
**/
XMSS_PrivateKey(XMSS_Parameters::xmss_algorithm_t xmss_algo_id,
size_t idx_leaf,
const secure_vector<uint8_t>& wots_priv_seed,
const secure_vector<uint8_t>& prf,
const secure_vector<uint8_t>& root,
const secure_vector<uint8_t>& public_seed)
: XMSS_PublicKey(xmss_algo_id, root, public_seed),
XMSS_Common_Ops(xmss_algo_id),
m_wots_priv_key(XMSS_PublicKey::m_xmss_params.ots_oid(),
public_seed,
wots_priv_seed),
m_prf(prf),
m_index_reg(XMSS_Index_Registry::get_instance())
{
set_unused_leaf_index(idx_leaf);
}
/**
* Retrieves the last unused leaf index of the private key. Reusing a leaf
* by utilizing leaf indices lower than the last unused leaf index will
* compromise security.
*
* @return Index of the last unused leaf.
**/
size_t unused_leaf_index() const
{
return *recover_global_leaf_index();
}
/**
* Sets the last unused leaf index of the private key. The leaf index
* will be updated automatically during every signing operation, and
* should not be set manually.
*
* @param idx Index of the last unused leaf.
**/
void set_unused_leaf_index(size_t idx)
{
if(idx >= (1ull << (XMSS_PublicKey::m_xmss_params.tree_height() - 1)))
{
throw Integrity_Failure("XMSS private key leaf index out of "
"bounds.");
}
else
{
std::atomic<size_t>& index =
static_cast<std::atomic<size_t>&>(*recover_global_leaf_index());
size_t current = 0;
do
{
current = index.load();
if(current > idx)
return;
}
while(!index.compare_exchange_strong(current, idx));
}
}
size_t reserve_unused_leaf_index()
{
size_t idx = (static_cast<std::atomic<size_t>&>(
*recover_global_leaf_index())).fetch_add(1);
if(idx >= (1ull << (XMSS_PublicKey::m_xmss_params.tree_height() - 1)))
{
throw Integrity_Failure("XMSS private key, one time signatures "
"exhausted.");
}
return idx;
}
/**
* Winternitz One Time Signature Scheme key utilized for signing
* operations.
*
* @return WOTS+ private key.
**/
const XMSS_WOTS_PrivateKey& wots_private_key() const
{
return m_wots_priv_key;
}
/**
* Winternitz One Time Signature Scheme key utilized for signing
* operations.
*
* @return WOTS+ private key.
**/
XMSS_WOTS_PrivateKey& wots_private_key()
{
return m_wots_priv_key;
}
const secure_vector<uint8_t>& prf() const
{
return m_prf;
}
secure_vector<uint8_t>& prf()
{
return m_prf;
}
virtual void set_public_seed(
const secure_vector<uint8_t>& public_seed) override
{
m_public_seed = public_seed;
m_wots_priv_key.set_public_seed(public_seed);
}
virtual void set_public_seed(secure_vector<uint8_t>&& public_seed) override
{
m_public_seed = std::move(public_seed);
m_wots_priv_key.set_public_seed(m_public_seed);
}
virtual const secure_vector<uint8_t>& public_seed() const override
{
return m_public_seed;
}
virtual std::unique_ptr<PK_Ops::Signature>
create_signature_op(RandomNumberGenerator&,
const std::string&,
const std::string& provider) const override;
virtual secure_vector<uint8_t> private_key_bits() const override
{
return raw_private_key();
}
virtual size_t size() const override
{
return XMSS_PublicKey::size() +
sizeof(uint64_t) +
2 * XMSS_PublicKey::m_xmss_params.element_size();
}
/**
* Generates a non standartized byte sequence representing the XMSS
* private key.
*
* @return byte sequence consisting of the following elements in order:
* 4-byte OID, n-byte root node, n-byte public seed,
* 8-byte unused leaf index, n-byte prf seed, n-byte private seed.
**/
virtual secure_vector<uint8_t> raw_private_key() const;
/**
* Algorithm 9: "treeHash"
* Computes the internal n-byte nodes of a Merkle tree.
*
* @param start_idx The start index.
* @param target_node_height Height of the target node.
* @param adrs Address of the tree containing the target node.
*
* @return The root node of a tree of height target_node height with the
* leftmost leaf being the hash of the WOTS+ pk with index
* start_idx.
**/
secure_vector<uint8_t> tree_hash(
size_t start_idx,
size_t target_node_height,
XMSS_Address& adrs);
private:
/**
* Fetches shared unused leaf index fromt the index registry
**/
std::shared_ptr<Atomic<size_t>> recover_global_leaf_index() const;
XMSS_WOTS_PrivateKey m_wots_priv_key;
secure_vector<uint8_t> m_prf;
XMSS_Index_Registry& m_index_reg;
};
}
#endif
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