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274 lines
12 KiB
C++
274 lines
12 KiB
C++
// Copyright (c) 2024, The Monero Project
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//
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modification, are
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// permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this list of
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// conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
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// of conditions and the following disclaimer in the documentation and/or other
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// materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
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// used to endorse or promote products derived from this software without specific
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// prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#pragma once
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#include "crypto/crypto.h"
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#include "misc_log_ex.h"
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#include "tower_cycle.h"
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#include <vector>
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namespace fcmp
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{
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namespace curve_trees
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{
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//----------------------------------------------------------------------------------------------------------------------
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//----------------------------------------------------------------------------------------------------------------------
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// Hash a chunk of new children
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template<typename C>
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typename C::Point get_new_parent(const C &curve, const typename C::Chunk &new_children);
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//----------------------------------------------------------------------------------------------------------------------
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// A layer of contiguous hashes starting from a specific start_idx in the tree
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template<typename C>
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struct LayerExtension final
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{
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std::size_t start_idx{0};
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bool update_existing_last_hash;
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std::vector<typename C::Point> hashes;
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};
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// A struct useful to trim a layer and update its last hash if necessary
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template<typename C>
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struct LayerReduction final
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{
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std::size_t new_total_parents{0};
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bool update_existing_last_hash;
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typename C::Point new_last_hash;
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};
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// Useful metadata for growing a layer
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struct GrowLayerInstructions final
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{
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// The max chunk width of children used to hash into a parent
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std::size_t parent_chunk_width;
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// Total children refers to the total number of elements in a layer
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std::size_t old_total_children;
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std::size_t new_total_children;
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// Total parents refers to the total number of hashes of chunks of children
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std::size_t old_total_parents;
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std::size_t new_total_parents;
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// When updating the tree, we use this boolean to know when we'll need to use the tree's existing old root in order
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// to set a new layer after that root
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// - We'll need to be sure the old root gets hashed when setting the next layer
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bool setting_next_layer_after_old_root;
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// When the last child in the child layer changes, we'll need to use its old value to update its parent hash
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bool need_old_last_child;
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// When the last parent in the layer changes, we'll need to use its old value to update itself
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bool need_old_last_parent;
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// The first chunk that needs to be updated's first child's offset within that chunk
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std::size_t start_offset;
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// The parent's starting index in the layer
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std::size_t next_parent_start_index;
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};
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// Useful metadata for trimming a layer
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struct TrimLayerInstructions final
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{
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// The max chunk width of children used to hash into a parent
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std::size_t parent_chunk_width;
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// Total children refers to the total number of elements in a layer
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std::size_t old_total_children;
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std::size_t new_total_children;
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// Total parents refers to the total number of hashes of chunks of children
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std::size_t old_total_parents;
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std::size_t new_total_parents;
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bool need_last_chunk_children_to_trim;
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bool need_last_chunk_remaining_children;
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bool need_last_chunk_parent;
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bool need_new_last_child;
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bool update_existing_last_hash;
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std::size_t new_offset;
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std::size_t hash_offset;
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std::size_t start_trim_idx;
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std::size_t end_trim_idx;
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};
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//----------------------------------------------------------------------------------------------------------------------
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//----------------------------------------------------------------------------------------------------------------------
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// This class is useful help update the curve trees tree without needing to keep the entire tree in memory
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// - It requires instantiation with the C1 and C2 curve classes and widths, hardening the tree structure
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// - It ties the C2 curve in the tree to the leaf layer
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template<typename C1, typename C2>
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class CurveTrees
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{
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public:
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CurveTrees(const C1 &c1, const C2 &c2, const std::size_t c1_width, const std::size_t c2_width):
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m_c1{c1},
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m_c2{c2},
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m_c1_width{c1_width},
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m_c2_width{c2_width},
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m_leaf_layer_chunk_width{LEAF_TUPLE_SIZE * c2_width}
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{
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assert(c1_width > 0);
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assert(c2_width > 0);
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};
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//member structs
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public:
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// Tuple that composes a single leaf in the tree
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struct LeafTuple final
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{
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// Output ed25519 point x-coordinate
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const typename C2::Scalar O_x;
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// Key image generator x-coordinate
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const typename C2::Scalar I_x;
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// Commitment x-coordinate
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const typename C2::Scalar C_x;
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};
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static const std::size_t LEAF_TUPLE_SIZE = 3;
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static_assert(sizeof(LeafTuple) == (sizeof(typename C2::Scalar) * LEAF_TUPLE_SIZE), "unexpected LeafTuple size");
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// Contiguous leaves in the tree, starting a specified start_idx in the leaf layer
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struct Leaves final
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{
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// Starting leaf tuple index in the leaf layer
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std::size_t start_leaf_tuple_idx{0};
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// Contiguous leaves in a tree that start at the start_idx
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std::vector<LeafTuple> tuples;
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};
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// A struct useful to extend an existing tree
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// - layers alternate between C1 and C2
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// - c2_layer_extensions[0] is first layer after leaves, then c1_layer_extensions[0], c2_layer_extensions[1], etc
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struct TreeExtension final
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{
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Leaves leaves;
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std::vector<LayerExtension<C1>> c1_layer_extensions;
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std::vector<LayerExtension<C2>> c2_layer_extensions;
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};
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// A struct useful to reduce the number of leaves in an existing tree
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// - layers alternate between C1 and C2
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// - c2_layer_reductions[0] is first layer after leaves, then c1_layer_reductions[0], c2_layer_reductions[1], etc
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struct TreeReduction final
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{
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std::size_t new_total_leaf_tuples;
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std::vector<LayerReduction<C1>> c1_layer_reductions;
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std::vector<LayerReduction<C2>> c2_layer_reductions;
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};
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// Last hashes from each layer in the tree
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// - layers alternate between C1 and C2
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// - c2_last_hashes[0] refers to the layer after leaves, then c1_last_hashes[0], then c2_last_hashes[1], etc
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struct LastHashes final
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{
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std::vector<typename C1::Point> c1_last_hashes;
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std::vector<typename C2::Point> c2_last_hashes;
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};
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// The children we'll trim from each last chunk in the tree
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// - layers alternate between C1 and C2
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// - c2_children[0] refers to the layer after leaves, then c1_children[0], then c2_children[1], etc
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struct LastChunkChildrenToTrim final
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{
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std::vector<std::vector<typename C1::Scalar>> c1_children;
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std::vector<std::vector<typename C2::Scalar>> c2_children;
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};
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//member functions
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public:
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// Convert cryptonote output pub key and commitment to a leaf tuple for the curve trees tree
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LeafTuple output_to_leaf_tuple(const crypto::public_key &O, const crypto::public_key &C) const;
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// Flatten leaves [(O.x, I.x, C.x),(O.x, I.x, C.x),...] -> [scalar,scalar,scalar,scalar,scalar,scalar,...]
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std::vector<typename C2::Scalar> flatten_leaves(const std::vector<LeafTuple> &leaves) const;
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// Take in the existing number of leaf tuples and the existing last hashes of each layer in the tree, as well as new
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// leaves to add to the tree, and return a tree extension struct that can be used to extend a tree
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TreeExtension get_tree_extension(const std::size_t old_n_leaf_tuples,
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const LastHashes &existing_last_hashes,
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const std::vector<LeafTuple> &new_leaf_tuples) const;
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// Get instructions useful for trimming all existing layers in the tree
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std::vector<TrimLayerInstructions> get_trim_instructions(
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const std::size_t old_n_leaf_tuples,
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const std::size_t trim_n_leaf_tuples) const;
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// Take in the instructions useful for trimming all existing layers in the tree, all children to be trimmed from
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// each last chunk, and the existing last hashes in what will become the new last parent of each layer, and return
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// a tree reduction struct that can be used to trim a tree
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TreeReduction get_tree_reduction(
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const std::vector<TrimLayerInstructions> &trim_instructions,
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const LastChunkChildrenToTrim &children_to_trim,
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const LastHashes &last_hashes) const;
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private:
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// Helper function used to set the next layer extension used to grow the next layer in the tree
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// - for example, if we just grew the parent layer after the leaf layer, the "next layer" would be the grandparent
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// layer of the leaf layer
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GrowLayerInstructions set_next_layer_extension(
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const GrowLayerInstructions &prev_layer_instructions,
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const bool parent_is_c1,
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const LastHashes &last_hashes,
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std::size_t &c1_last_idx_inout,
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std::size_t &c2_last_idx_inout,
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TreeExtension &tree_extension_inout) const;
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//public member variables
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public:
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// The curve interfaces
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const C1 &m_c1;
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const C2 &m_c2;
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// The leaf layer has a distinct chunk width than the other layers
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// TODO: public function for update_last_parent, and make this private
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const std::size_t m_leaf_layer_chunk_width;
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// The chunk widths of the layers in the tree tied to each curve
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const std::size_t m_c1_width;
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const std::size_t m_c2_width;
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};
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//----------------------------------------------------------------------------------------------------------------------
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using Helios = tower_cycle::Helios;
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using Selene = tower_cycle::Selene;
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using CurveTreesV1 = CurveTrees<Helios, Selene>;
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// https://github.com/kayabaNerve/fcmp-plus-plus/blob
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// /b2742e86f3d18155fd34dd1ed69cb8f79b900fce/crypto/fcmps/src/tests.rs#L81-L82
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static const std::size_t HELIOS_CHUNK_WIDTH = 38;
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static const std::size_t SELENE_CHUNK_WIDTH = 18;
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static const Helios HELIOS;
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static const Selene SELENE;
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static const CurveTreesV1 curve_trees_v1(HELIOS, SELENE, HELIOS_CHUNK_WIDTH, SELENE_CHUNK_WIDTH);
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//----------------------------------------------------------------------------------------------------------------------
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//----------------------------------------------------------------------------------------------------------------------
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} //namespace curve_trees
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} //namespace fcmp
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