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/*
* SLH-DSA treehash logic
* (C) 2023 Jack Lloyd
* 2023 Fabian Albert, René Meusel, Amos Treiber - Rohde & Schwarz Cybersecurity
*
*
* Botan is released under the Simplified BSD License (see license.txt)
**/
#ifndef BOTAN_SP_TREEHASH_H_
#define BOTAN_SP_TREEHASH_H_
#include <botan/sp_parameters.h>
#include <botan/internal/sp_types.h>
#include <functional>
#include <optional>
namespace Botan {
class Sphincs_Address;
class Sphincs_Hash_Functions;
using GenerateLeafFunction = std::function<void(StrongSpan<SphincsTreeNode> /* leaf out parameter */, TreeNodeIndex)>;
/**
* Implements a generic Merkle tree hash. Will be used for both FORS and XMSS
* signatures.
* @p gen_leaf is used to create leaf nodes in the respective trees.
* Additionally XMSS uses the gen_leaf logic to store the WOTS Signature in the
* main SLH-DSA signature. The @p leaf_idx is the index of leaf to sign. If
* only the root node must be computed (without a signature), the @p leaf_idx is
* set to std::nullopt.
*/
BOTAN_TEST_API void treehash(StrongSpan<SphincsTreeNode> out_root,
StrongSpan<SphincsAuthenticationPath> out_auth_path,
const Sphincs_Parameters& params,
Sphincs_Hash_Functions& hashes,
std::optional<TreeNodeIndex> leaf_idx,
uint32_t idx_offset,
uint32_t tree_height,
const GenerateLeafFunction& gen_leaf,
Sphincs_Address& tree_address);
/**
* Using a leaf node and the authentication path (neighbor nodes on the way from
* leaf to root), computes the the root node of the respective tree. This
* function is generic and used by FORS and XMSS in the SLH-DSA verification
* logic.
*/
BOTAN_TEST_API void compute_root(StrongSpan<SphincsTreeNode> out,
const Sphincs_Parameters& params,
Sphincs_Hash_Functions& hashes,
const SphincsTreeNode& leaf,
TreeNodeIndex leaf_idx,
uint32_t idx_offset,
StrongSpan<const SphincsAuthenticationPath> authentication_path,
uint32_t tree_height,
Sphincs_Address& tree_address);
} // namespace Botan
#endif