├── .travis.yml ├── doc ├── cachesize.png └── auditpathgen.png ├── .gitignore ├── util.go ├── gosmt_test.go ├── README.md ├── cmd ├── benchht │ └── main.go └── benchsmt │ └── main.go ├── cache.go ├── gosmt.go └── LICENSE /.travis.yml: -------------------------------------------------------------------------------- 1 | language: go 2 | 3 | go: 4 | - tip 5 | -------------------------------------------------------------------------------- /doc/cachesize.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/pylls/gosmt/HEAD/doc/cachesize.png -------------------------------------------------------------------------------- /doc/auditpathgen.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/pylls/gosmt/HEAD/doc/auditpathgen.png -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | # Compiled Object files, Static and Dynamic libs (Shared Objects) 2 | *.o 3 | *.a 4 | *.so 5 | 6 | # Folders 7 | _obj 8 | _test 9 | 10 | # Architecture specific extensions/prefixes 11 | *.[568vq] 12 | [568vq].out 13 | 14 | *.cgo1.go 15 | *.cgo2.c 16 | _cgo_defun.c 17 | _cgo_gotypes.go 18 | _cgo_export.* 19 | 20 | _testmain.go 21 | 22 | *.exe 23 | *.test 24 | *.prof 25 | *.out 26 | -------------------------------------------------------------------------------- /util.go: -------------------------------------------------------------------------------- 1 | package gosmt 2 | 3 | import "crypto/sha512" 4 | 5 | // thank you https://play.golang.org/p/sycUxCZyxf. 6 | 7 | // bitIsSet checks whether bit of a bit string (stored as a byte string) 8 | // at position i (range:[1, N] and big-endian) is set to 1 . 9 | func bitIsSet(bits []byte, i uint64) bool { return bits[i/8]&(1< 41 | 42 |

43 | 44 | There is no such thing as a free lunch though. Below is the average time it 45 | takes to generate an (Merkle) audit path. We include a number of B- caches with 46 | different caching probabilities (note that the B cache is identical to B-1.0). 47 | While B-0.5 behaves erratic, B-0.6 and above needs less then 4ms. For many 48 | applications this is practical and saves a significant amount of space compared 49 | to explicity stored authenticated data structures. 50 | 51 |

52 | 53 |

54 | 55 | You can reproduce these benchmarks with the 56 | [cmd/benchht](https://github.com/pylls/gosmt/tree/master/cmd/benchht) and 57 | [cmd/benchsmt](https://github.com/pylls/gosmt/tree/master/cmd/benchsmt) 58 | executables. 59 | 60 | #### Paper 61 | [https://eprint.iacr.org/2016/683](https://eprint.iacr.org/2016/683) 62 | 63 | #### License 64 | Apache 2.0 65 | -------------------------------------------------------------------------------- /cmd/benchht/main.go: -------------------------------------------------------------------------------- 1 | package main 2 | 3 | import ( 4 | "crypto/sha512" 5 | "fmt" 6 | "log" 7 | "math/rand" 8 | "testing" 9 | 10 | "github.com/pylls/balloon/hashtreap" 11 | ) 12 | 13 | type run struct { 14 | f func(b *testing.B) 15 | cache string 16 | size int 17 | } 18 | 19 | var ( 20 | maxSize = 20 21 | hashOutputLen = 32 22 | updateSize = 256 23 | keyUpdateDSsize = 15 24 | ) 25 | 26 | func main() { 27 | log.Printf("update time (ms) for keys in 2^%d HT:", keyUpdateDSsize) 28 | for i := uint(1); i <= uint(maxSize); i++ { 29 | result := testing.Benchmark(makeUpdateKeysBench(1<= s 36 | i := sort.Search(d.Len(), func(i int) bool { 37 | return bytes.Compare(d[i], s) >= 0 38 | }) 39 | return d[:i], d[i:] 40 | } 41 | 42 | // Key also implements Trie interface, splitable on split index. 43 | type Key [][]byte 44 | 45 | func (k Key) Len() int { return len(k) } 46 | func (k Key) Swap(i, j int) { k[i], k[j] = k[j], k[i] } 47 | func (k Key) Less(i, j int) bool { return bytes.Compare(k[i], k[j]) == -1 } 48 | func (k Key) Split(s []byte) (l, r Key) { 49 | // make sure k is stable-sorted first 50 | sort.Stable(k) 51 | // the smallest index i where d[i] >= s 52 | i := sort.Search(k.Len(), func(i int) bool { 53 | return bytes.Compare(k[i], s) >= 0 54 | }) 55 | return k[:i], k[i:] 56 | } 57 | 58 | // SMT is a sparse Merkle tree. 59 | type SMT struct { 60 | c []byte // tree-wide constant, an empty leaf will have a default value of hash(c) 61 | cache Cache // Cache interface could be implemented by different caching strategies 62 | Base []byte // key of left-most leaf of a subtree, fixed in size. 63 | hash func(data ...[]byte) []byte 64 | N uint64 // output length, in bits, of hash 65 | defaultHashes [][]byte // [height][]byte, one default byte string per height (range:[0, N]), leaf node has height of 0, root node has height of N. 66 | } 67 | 68 | // NewSMT creates a new SMT. SMT instantiation requires a default empty leaf constant c, a caching strategy cache (e.g. CacheBranch, CacheBranchPlus), and a particular hash function (e.g. SHA256) 69 | func NewSMT(c []byte, cache Cache, hash func(data ...[]byte) []byte) *SMT { 70 | s := new(SMT) 71 | s.cache = cache 72 | s.hash = hash 73 | s.c = c 74 | s.N = uint64(len(hash([]byte("smt"))) * 8) // hash any string to get output length 75 | s.Base = make([]byte, s.N/8) 76 | 77 | s.defaultHashes = make([][]byte, s.N+1) 78 | s.defaultHashes[0] = s.leafHash(Empty, nil) 79 | for i := 1; i <= int(s.N); i++ { 80 | s.defaultHashes[i] = hash(s.defaultHashes[i-1], s.defaultHashes[i-1]) 81 | } 82 | return s 83 | } 84 | 85 | // Update updates keys to the value. Note: d and keys should be sorted as param. 86 | func (s *SMT) Update(d D, keys Key, height uint64, base, value []byte) []byte { 87 | if height == 0 { 88 | return s.leafHash(value, base) 89 | } 90 | split := bitSplit(base, s.N-height) 91 | ld, rd := d.Split(split) 92 | lkeys, rkeys := keys.Split(split) 93 | 94 | // When there's a key falling within the range of left/right subtree, meaning 95 | // a leaf node in left/right branch should be updated to a new value, then update 96 | // the root hash of left/right subtree recursively; 97 | // When no leaf node in left/right subtree shall be updated, then directly return 98 | // its root hash and update upwards recursively. 99 | switch { 100 | case lkeys.Len() == 0 && rkeys.Len() > 0: 101 | return s.cache.HashCache(s.RootHash(ld, height-1, base), 102 | s.Update(rd, keys, height-1, split, value), 103 | height, base, split, s.interiorHash, s.defaultHashes) 104 | case lkeys.Len() > 0 && rkeys.Len() == 0: 105 | return s.cache.HashCache(s.Update(ld, keys, height-1, base, value), 106 | s.RootHash(rd, height-1, split), 107 | height, base, split, s.interiorHash, s.defaultHashes) 108 | default: 109 | return s.cache.HashCache(s.Update(ld, lkeys, height-1, base, value), 110 | s.Update(rd, rkeys, height-1, split, value), 111 | height, base, split, s.interiorHash, s.defaultHashes) 112 | } 113 | } 114 | 115 | // AuditPath generates an audit path. 116 | func (s *SMT) AuditPath(d D, height uint64, base, key []byte) [][]byte { 117 | if height == 0 { 118 | return nil 119 | } 120 | split := bitSplit(base, s.N-height) 121 | l, r := d.Split(split) 122 | 123 | if !bitIsSet(key, s.N-height) { // if k_j == 0 124 | return append(s.AuditPath(l, height-1, base, key), 125 | s.RootHash(r, height-1, split)) 126 | } 127 | return append(s.AuditPath(r, height-1, split, key), 128 | s.RootHash(l, height-1, base)) 129 | } 130 | 131 | // VerifyAuditPath verifies an audit path. 132 | func (s *SMT) VerifyAuditPath(ap [][]byte, key, value, root []byte) bool { 133 | return bytes.Equal(root, 134 | s.auditPathCalc(ap, s.N, make([]byte, s.N/8), key, value)) 135 | } 136 | 137 | func (s *SMT) auditPathCalc(ap [][]byte, height uint64, 138 | base, key, value []byte) []byte { 139 | if height == 0 { 140 | return s.leafHash(value, base) 141 | } 142 | split := bitSplit(base, s.N-height) 143 | if !bitIsSet(key, s.N-height) { // if k_j == 0 144 | return s.interiorHash(s.auditPathCalc(ap, height-1, base, key, value), 145 | ap[height-1], height, base) 146 | } 147 | return s.interiorHash(ap[height-1], 148 | s.auditPathCalc(ap, height-1, split, key, value), height, base) 149 | } 150 | 151 | // RootHash returns the root hash of a subtree with certain height. 152 | func (s *SMT) RootHash(d D, height uint64, base []byte) []byte { 153 | switch { 154 | case s.cache.Exists(height, base): 155 | return s.cache.Get(height, base) 156 | case d.Len() == 0: 157 | return s.defaultHash(height) 158 | case d.Len() == 1 && height == 0: 159 | return s.leafHash(Set, base) 160 | case d.Len() > 0 && height == 0: 161 | panic("this should never happen (unsorted D or broken split?)") 162 | default: 163 | split := bitSplit(base, s.N-height) 164 | l, r := d.Split(split) 165 | return s.interiorHash(s.RootHash(l, height-1, base), 166 | s.RootHash(r, height-1, split), height, base) 167 | } 168 | } 169 | 170 | func (s *SMT) defaultHash(height uint64) []byte { 171 | return s.defaultHashes[height] 172 | } 173 | 174 | // leafHash returns the leaf value of SMT. 175 | func (s *SMT) leafHash(a, base []byte) []byte { 176 | if bytes.Equal(a, Empty) { 177 | return s.hash(s.c) 178 | } 179 | return s.hash(s.c, base) 180 | } 181 | 182 | // interiorHash returns the non-leaf node value of SMT. 183 | func (s *SMT) interiorHash(left, right []byte, 184 | height uint64, base []byte) []byte { 185 | if bytes.Equal(left, right) { 186 | return s.hash(left, right) 187 | } 188 | buf := new(bytes.Buffer) 189 | if binary.Write(buf, binary.BigEndian, height) != nil { 190 | panic("failed to encode height") 191 | } 192 | return s.hash(left, right, base, buf.Bytes()) 193 | } 194 | 195 | // CacheEntries returns the number of cache entries. 196 | func (s *SMT) CacheEntries() int { 197 | return s.cache.Entries() 198 | } 199 | -------------------------------------------------------------------------------- /cmd/benchsmt/main.go: -------------------------------------------------------------------------------- 1 | package main 2 | 3 | import ( 4 | "crypto/sha512" 5 | "flag" 6 | "fmt" 7 | "log" 8 | "math/rand" 9 | "os" 10 | "sort" 11 | "strconv" 12 | "testing" 13 | "time" 14 | 15 | "github.com/montanaflynn/stats" 16 | "github.com/pylls/gosmt" 17 | ) 18 | 19 | type run struct { 20 | f func(b *testing.B) 21 | s func() string 22 | cache string 23 | } 24 | 25 | var ( 26 | maxSMT = 20 27 | keyUpdateDSsize = 15 28 | bMin = 0.5 29 | bMax = 0.9 30 | bDelta = 0.1 31 | updateSize = 256 32 | filename = "benchsmt." + time.Now().String() 33 | data []gosmt.D 34 | repeat = 4 35 | ) 36 | 37 | type res struct { 38 | index int 39 | ms float64 40 | } 41 | 42 | func main() { 43 | flag.Parse() 44 | if len(flag.Args()) == 0 { 45 | log.Fatal("need to specify maximum size of SMT") 46 | } 47 | m, err := strconv.Atoi(flag.Arg(0)) 48 | if err != nil { 49 | log.Fatal("the first argument has to be an int") 50 | } 51 | maxSMT = m 52 | file, err := os.OpenFile(filename, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0666) 53 | if err != nil { 54 | panic(err) 55 | } 56 | defer file.Close() 57 | 58 | // generate testdata only once 59 | for i := uint(1); i <= uint(maxSMT); i++ { 60 | var d gosmt.D 61 | size := 1 << i 62 | for j := 0; j < size; j++ { 63 | d = append(d, hash(randKey(make([]byte, 32)))) 64 | } 65 | sort.Sort(gosmt.D(d)) 66 | data = append(data, d) 67 | } 68 | 69 | var benchAP []run 70 | for i := 0; i < maxSMT; i++ { 71 | for j := bMin; j <= bMax; j += bDelta { 72 | benchAP = append(benchAP, run{ 73 | f: makeAuditPathBench(data[i], 74 | gosmt.NewCacheBranchMinus(j)), 75 | cache: fmt.Sprintf("B-%.1f", j), 76 | }) 77 | } 78 | benchAP = append(benchAP, run{ 79 | f: makeAuditPathBench(data[i], 80 | gosmt.CacheBranch(make(map[string][]byte))), 81 | cache: "B", 82 | }) 83 | benchAP = append(benchAP, run{ 84 | f: makeAuditPathBench(data[i], 85 | gosmt.CacheBranchPlus(make(map[string][]byte))), 86 | cache: "B+", 87 | }) 88 | } 89 | 90 | var benchUpdate []run 91 | for i := 0; i < maxSMT; i++ { 92 | for j := bMin; j <= bMax; j += bDelta { 93 | benchUpdate = append(benchUpdate, run{ 94 | f: makeUpdateBench(data[i], gosmt.NewCacheBranchMinus(j)), 95 | cache: fmt.Sprintf("B-%.1f", j), 96 | }) 97 | } 98 | benchUpdate = append(benchUpdate, run{ 99 | f: makeUpdateBench(data[i], 100 | gosmt.CacheBranch(make(map[string][]byte))), 101 | cache: "B", 102 | }) 103 | benchUpdate = append(benchUpdate, run{ 104 | f: makeUpdateBench(data[i], 105 | gosmt.CacheBranchPlus(make(map[string][]byte))), 106 | cache: "B+", 107 | }) 108 | } 109 | 110 | var benchUpdateKey []run 111 | for i := 0; i < maxSMT; i++ { 112 | size := 1 << uint(i+1) 113 | for j := bMin; j <= bMax; j += bDelta { 114 | benchUpdateKey = append(benchUpdateKey, run{ 115 | f: makeUpdateKeyBench(size, data[keyUpdateDSsize-1], 116 | gosmt.NewCacheBranchMinus(j)), 117 | cache: fmt.Sprintf("B-%.1f", j), 118 | }) 119 | } 120 | benchUpdateKey = append(benchUpdateKey, run{ 121 | f: makeUpdateKeyBench(size, data[keyUpdateDSsize-1], 122 | gosmt.CacheBranch(make(map[string][]byte))), 123 | cache: "B", 124 | }) 125 | benchUpdateKey = append(benchUpdateKey, run{ 126 | f: makeUpdateKeyBench(size, data[keyUpdateDSsize-1], 127 | gosmt.CacheBranchPlus(make(map[string][]byte))), 128 | cache: "B+", 129 | }) 130 | } 131 | 132 | var benchCacheSize []run 133 | for i := 0; i < maxSMT; i++ { 134 | for j := bMin; j <= bMax; j += bDelta { 135 | benchCacheSize = append(benchCacheSize, run{ 136 | s: makeCacheSizeBench(data[i], 137 | gosmt.NewCacheBranchMinus(j)), 138 | cache: fmt.Sprintf("B-%.1f", j), 139 | }) 140 | } 141 | benchCacheSize = append(benchCacheSize, run{ 142 | s: makeCacheSizeBench(data[i], 143 | gosmt.CacheBranch(make(map[string][]byte))), 144 | cache: "B", 145 | }) 146 | benchCacheSize = append(benchCacheSize, run{ 147 | s: makeCacheSizeBench(data[i], 148 | gosmt.CacheBranchPlus(make(map[string][]byte))), 149 | cache: "B+", 150 | }) 151 | } 152 | 153 | do(fmt.Sprintf("update time (ms) for 2^i keys in 2^%d SMT", keyUpdateDSsize), 154 | benchUpdateKey, file) 155 | do(fmt.Sprintf("update time (ms) for %d keys", updateSize), benchUpdate, file) 156 | do("cache size (MiB)", benchCacheSize, file) 157 | do("audit path generation time (ms)", benchAP, file) 158 | 159 | } 160 | 161 | func do(exp string, bench []run, file *os.File) { 162 | flog(fmt.Sprintf("####### experiment: %s #######", exp), file) 163 | expCount := len(bench) / maxSMT 164 | header := "SMT size 2^x" 165 | for i := 0; i < expCount; i++ { 166 | header += fmt.Sprintf(", %s", bench[i].cache) 167 | } 168 | flog(header, file) 169 | 170 | for i := 0; i < maxSMT; i++ { 171 | r := fmt.Sprintf("%d", i+1) 172 | for j := 0; j < expCount; j++ { 173 | if bench[i].s != nil { 174 | r += fmt.Sprintf(", %s", bench[i*expCount+j].s()) 175 | } else { 176 | results := make([]float64, repeat) 177 | for round := 0; round < repeat; round++ { 178 | results[round] = float64(testing.Benchmark(bench[i*expCount+j].f).NsPerOp()) / float64(1000*1000) // ns to ms 179 | } 180 | avg, err := stats.LoadRawData(results).Mean() 181 | if err != nil { 182 | panic(err) 183 | } 184 | r += fmt.Sprintf(", %.4f", avg) 185 | } 186 | } 187 | flog(r, file) 188 | } 189 | } 190 | 191 | func flog(str string, f *os.File) { 192 | _, err := f.WriteString(str + "\n") 193 | if err != nil { 194 | panic(err) 195 | } 196 | log.Println(str) 197 | } 198 | 199 | func makeAuditPathBench(data gosmt.D, 200 | cache gosmt.Cache) func(b *testing.B) { 201 | return func(b *testing.B) { 202 | s := gosmt.NewSMT([]byte{0x42}, cache, hash) 203 | s.Update(data, gosmt.Key(data), s.N, s.Base, gosmt.Set) 204 | 205 | // create N keys 206 | keys := make([][]byte, b.N) 207 | for i := 0; i < b.N; i++ { 208 | keys[i] = randKey(make([]byte, s.N/8)) 209 | } 210 | 211 | b.ResetTimer() 212 | for i := 0; i < b.N; i++ { 213 | s.AuditPath(data, s.N, s.Base, keys[i]) 214 | } 215 | } 216 | } 217 | 218 | func makeUpdateBench(data gosmt.D, 219 | cache gosmt.Cache) func(b *testing.B) { 220 | return func(b *testing.B) { 221 | s := gosmt.NewSMT([]byte{0x42}, cache, hash) 222 | s.Update(data, gosmt.Key(data), s.N, s.Base, gosmt.Set) 223 | 224 | // create updateSize keys 225 | keys := make([][]byte, updateSize) 226 | for i := 0; i < updateSize; i++ { 227 | keys[i] = randKey(make([]byte, s.N/8)) 228 | } 229 | newdata := make([][]byte, len(data), len(data)+len(keys)) 230 | copy(newdata, data) 231 | newdata = append(newdata, keys...) 232 | sort.Sort(gosmt.D(newdata)) 233 | 234 | b.ResetTimer() 235 | for i := 0; i < b.N; i++ { 236 | s.Update(newdata, keys, s.N, s.Base, gosmt.Set) 237 | b.StopTimer() 238 | s.Update(data, keys, s.N, s.Base, gosmt.Empty) 239 | b.StartTimer() 240 | } 241 | } 242 | } 243 | 244 | func makeUpdateKeyBench(size int, data gosmt.D, 245 | cache gosmt.Cache) func(b *testing.B) { 246 | return func(b *testing.B) { 247 | s := gosmt.NewSMT([]byte{0x42}, cache, hash) 248 | s.Update(data, gosmt.Key(data), s.N, s.Base, gosmt.Set) 249 | 250 | b.ResetTimer() 251 | for i := 0; i < b.N; i++ { 252 | b.StopTimer() 253 | 254 | keys := make([][]byte, size) 255 | for i := 0; i < size; i++ { 256 | keys[i] = randKey(make([]byte, s.N/8)) 257 | } 258 | newdata := make([][]byte, len(data), len(data)+len(keys)) 259 | copy(newdata, data) 260 | newdata = append(newdata, keys...) 261 | sort.Sort(gosmt.D(newdata)) 262 | 263 | b.StartTimer() 264 | s.Update(newdata, keys, s.N, s.Base, gosmt.Set) 265 | 266 | b.StopTimer() 267 | // cleanup, remove the keys we just inserted 268 | s.Update(data, keys, s.N, s.Base, gosmt.Empty) 269 | b.StartTimer() 270 | } 271 | } 272 | } 273 | 274 | func makeCacheSizeBench(data gosmt.D, 275 | cache gosmt.Cache) func() string { 276 | return func() string { 277 | s := gosmt.NewSMT([]byte{0x42}, cache, hash) 278 | s.Update(data, gosmt.Key(data), s.N, s.Base, gosmt.Set) 279 | 280 | return fmt.Sprintf("%.4f", 281 | float64(s.CacheEntries()*int(s.N))/float64(1024*1024)) 282 | } 283 | } 284 | 285 | func randKey(key []byte) []byte { 286 | _, err := rand.Read(key) 287 | if err != nil { 288 | panic(err) 289 | } 290 | return key 291 | } 292 | 293 | func hash(data ...[]byte) []byte { 294 | hasher := sha512.New512_256() 295 | for i := 0; i < len(data); i++ { 296 | hasher.Write(data[i]) 297 | } 298 | return hasher.Sum(nil) 299 | } 300 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, 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