neptune-mutator-set 0.14.0

The mutator set, a privacy-preserving cryptographic accumulator invented by the Neptune team. Paper: https://eprint.iacr.org/2023/1208 Article: https://neptune.cash/articles/mutator-sets
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198

use tasm_lib::twenty_first::util_types::mmr::mmr_accumulator::MmrAccumulator;
use tasm_lib::twenty_first::util_types::mmr::mmr_membership_proof::MmrMembershipProof;

#[derive(Debug, Clone)]
pub struct MmraAndMembershipProofs {
    pub mmra: MmrAccumulator,
    pub membership_proofs: Vec<MmrMembershipProof>,
    pub leaf_indices: Vec<u64>,
}

#[cfg(any(test, feature = "arbitrary-impls"))]
pub mod neptune_arbitrary {
    use itertools::Itertools;
    use proptest::arbitrary::Arbitrary;
    use proptest::strategy::BoxedStrategy;
    use proptest::strategy::Just;
    use proptest::strategy::Strategy;
    use tasm_lib::prelude::Digest;
    use tasm_lib::twenty_first::util_types::mmr::shared_basic::leaf_index_to_mt_index_and_peak_index;

    use super::super::root_and_paths::RootAndPaths;
    use super::*;

    impl Arbitrary for MmraAndMembershipProofs {
        type Parameters = (Vec<(u64, Digest)>, u64);

        fn arbitrary_with(parameters: Self::Parameters) -> Self::Strategy {
            let (indices_and_leafs, total_leaf_count) = parameters;
            let indices = indices_and_leafs.iter().map(|(i, _d)| *i).collect_vec();
            let leafs = indices_and_leafs.iter().map(|(_i, d)| *d).collect_vec();
            let num_paths = leafs.len() as u64;

            let num_peaks = total_leaf_count.count_ones();
            let mut tree_heights = vec![];
            for shift in (0..64).rev() {
                if total_leaf_count & (1u64 << shift) != 0 {
                    tree_heights.push(shift);
                }
            }

            // sample mmr leaf indices and calculate matching derived indices
            let index_sets = leafs
                .iter()
                .enumerate()
                .map(|(enumeration_index, _leaf)| (enumeration_index, indices[enumeration_index]))
                .map(|(enumeration_index, mmr_leaf_index)| {
                    let (mt_node_index, peak_index) =
                        leaf_index_to_mt_index_and_peak_index(mmr_leaf_index, total_leaf_count);
                    (enumeration_index, mt_node_index, mmr_leaf_index, peak_index)
                })
                .collect_vec();
            let leafs_and_indices = leafs
                .iter()
                .copied()
                .zip(index_sets.iter().copied())
                .collect_vec();

            // segregate by tree
            let mut indices_and_leafs_by_tree = vec![];
            for tree in 0..num_peaks {
                let local_indices_and_leafs = leafs_and_indices
                    .iter()
                    .filter(
                        |(
                            _leaf,
                            (_enumeration_index, _mt_node_index, _mmr_leaf_index, peak_index),
                        )| { *peak_index == tree },
                    )
                    .copied()
                    .map(
                        |(
                            leaf,
                            (enumeration_index, mt_node_index, mmr_leaf_index, _peak_index),
                        )| {
                            (enumeration_index, mt_node_index, mmr_leaf_index, leaf)
                        },
                    )
                    .collect_vec();

                indices_and_leafs_by_tree.push(local_indices_and_leafs);
            }

            // for each tree generate root and paths
            let mut root_and_paths_strategies = vec![];
            for (tree, local_indices_and_leafs) in indices_and_leafs_by_tree.iter().enumerate() {
                let tree_height = tree_heights[tree];
                let root_and_paths_strategy = RootAndPaths::arbitrary_with((
                    tree_height,
                    local_indices_and_leafs
                        .iter()
                        .copied()
                        .map(|(_ei, mtni, _mmri, leaf)| (mtni ^ (1 << tree_height), leaf))
                        .collect_vec(),
                ));
                root_and_paths_strategies.push(root_and_paths_strategy);
            }

            // unwrap vector of roots and pathses
            (root_and_paths_strategies, Just(indices_and_leafs_by_tree))
                .prop_map(move |(roots_and_pathses, indices_and_leafs_by_tree_)| {
                    // extract peaks
                    let peaks = roots_and_pathses
                        .iter()
                        .map(|root_and_paths| root_and_paths.root)
                        .collect_vec();

                    // prepare to extract membership proofs
                    let mut membership_proofs = vec![
                        MmrMembershipProof {
                            authentication_path: vec![],
                        };
                        num_paths as usize
                    ];
                    let mut leaf_indices = vec![0; num_paths as usize];

                    // loop over all leaf indices and look up membership proof
                    for (root_and_paths, indices_and_leafs_) in roots_and_pathses
                        .into_iter()
                        .zip(indices_and_leafs_by_tree_.iter())
                    {
                        let paths = root_and_paths.paths;
                        for (path, &(enumeration_index, _merkle_tree_index, mmr_index, _leaf)) in
                            paths.into_iter().zip(indices_and_leafs_.iter())
                        {
                            membership_proofs[enumeration_index].authentication_path = path;
                            leaf_indices[enumeration_index] = mmr_index;
                        }
                    }

                    // sanity check
                    for ((mmr_mp, leaf), leaf_index) in membership_proofs
                        .iter()
                        .zip(leafs.iter())
                        .zip(leaf_indices.iter())
                    {
                        let (_mti, _pi) =
                            leaf_index_to_mt_index_and_peak_index(*leaf_index, total_leaf_count);
                        assert!(mmr_mp.verify(*leaf_index, *leaf, &peaks, total_leaf_count));
                    }

                    MmraAndMembershipProofs {
                        mmra: MmrAccumulator::init(peaks, total_leaf_count),
                        membership_proofs,
                        leaf_indices,
                    }
                })
                .boxed()
        }

        type Strategy = BoxedStrategy<Self>;
    }
}

#[cfg(test)]
#[cfg_attr(coverage_nightly, coverage(off))]
mod tests {
    use itertools::Itertools;
    use proptest::collection::vec;
    use proptest::prelude::*;
    use proptest_arbitrary_interop::arb;
    use tasm_lib::twenty_first::prelude::Digest;
    use tasm_lib::twenty_first::util_types::mmr::mmr_trait::Mmr;
    use test_strategy::proptest;

    use super::*;

    fn indices_and_leafs_strategy(max: u64, num: usize) -> BoxedStrategy<Vec<(u64, Digest)>> {
        vec((0u64..max, arb::<Digest>()), num)
            .prop_filter("indices must all be unique", |indices_and_leafs| {
                indices_and_leafs.iter().map(|(i, _l)| *i).all_unique()
            })
            .boxed()
    }

    #[proptest(cases = 20)]
    fn integrity(
        #[strategy(1usize..10)] _num_paths: usize,
        #[strategy(0..u64::MAX)] _total_leaf_count: u64,
        #[strategy(indices_and_leafs_strategy(#_total_leaf_count, #_num_paths))]
        indices_and_leafs: Vec<(u64, Digest)>,
        #[strategy(
            MmraAndMembershipProofs::arbitrary_with((#indices_and_leafs, #_total_leaf_count))
        )]
        mmra_and_membership_proofs: MmraAndMembershipProofs,
    ) {
        for ((index, leaf), mp) in indices_and_leafs
            .into_iter()
            .zip(mmra_and_membership_proofs.membership_proofs)
        {
            prop_assert!(mp.verify(
                index,
                leaf,
                &mmra_and_membership_proofs.mmra.peaks(),
                mmra_and_membership_proofs.mmra.num_leafs(),
            ));
        }
    }
}