hermez-node/common/zk.go
common/zk.goRaw
1// Package common contains all the common data structures used at the
2// hermez-node, zk.go contains the zkSnark inputs used to generate the proof
3package common
4
5import (
6 "crypto/sha256"
7 "encoding/binary"
8 "encoding/json"
9 "fmt"
10 "math/big"
11
12 "github.com/hermeznetwork/hermez-node/log"
13 "github.com/hermeznetwork/tracerr"
14 cryptoConstants "github.com/iden3/go-iden3-crypto/constants"
15 "github.com/iden3/go-merkletree"
16 "github.com/mitchellh/mapstructure"
17)
18
19// ZKMetadata contains ZKInputs metadata that is not used directly in the
20// ZKInputs result, but to calculate values for Hash check
21type ZKMetadata struct {
22 // Circuit parameters
23 // absolute maximum of L1 or L2 transactions allowed
24 NTx uint32
25 // merkle tree depth
26 NLevels uint32
27 MaxLevels uint32
28 // absolute maximum of L1 transaction allowed
29 MaxL1Tx uint32
30 // total txs allowed
31 MaxTx uint32
32 // Maximum number of Idxs where Fees can be send in a batch (currently
33 // is constant for all circuits: 64)
34 MaxFeeIdxs uint32
35
36 L1TxsData [][]byte
37 L1TxsDataAvailability [][]byte
38 L2TxsData [][]byte
39 ChainID uint16
40
41 NewLastIdxRaw Idx
42 NewStateRootRaw *merkletree.Hash
43 NewExitRootRaw *merkletree.Hash
44}
45
46// ZKInputs represents the inputs that will be used to generate the zkSNARK proof
47type ZKInputs struct {
48 Metadata ZKMetadata `json:"-"`
49
50 //
51 // General
52 //
53
54 // CurrentNumBatch is the current batch number processed
55 CurrentNumBatch *big.Int `json:"currentNumBatch"` // uint32
56 // inputs for final `hashGlobalInputs`
57 // OldLastIdx is the last index assigned to an account
58 OldLastIdx *big.Int `json:"oldLastIdx"` // uint64 (max nLevels bits)
59 // OldStateRoot is the current state merkle tree root
60 OldStateRoot *big.Int `json:"oldStateRoot"` // Hash
61 // GlobalChainID is the blockchain ID (0 for Ethereum mainnet). This value can be get from the smart contract.
62 GlobalChainID *big.Int `json:"globalChainID"` // uint16
63 // FeeIdxs is an array of merkle tree indexes where the coordinator will receive the accumulated fees
64 FeeIdxs []*big.Int `json:"feeIdxs"` // uint64 (max nLevels bits), len: [maxFeeIdxs]
65
66 // accumulate fees
67 // FeePlanTokens contains all the tokenIDs for which the fees are being accumulated
68 FeePlanTokens []*big.Int `json:"feePlanTokens"` // uint32 (max 32 bits), len: [maxFeeIdxs]
69
70 //
71 // Txs (L1&L2)
72 //
73
74 // transaction L1-L2
75 // TxCompressedData
76 TxCompressedData []*big.Int `json:"txCompressedData"` // big.Int (max 251 bits), len: [nTx]
77 // TxCompressedDataV2, only used in L2Txs, in L1Txs is set to 0
78 TxCompressedDataV2 []*big.Int `json:"txCompressedDataV2"` // big.Int (max 193 bits), len: [nTx]
79 // MaxNumBatch is the maximum allowed batch number when the transaction
80 // can be processed
81 MaxNumBatch []*big.Int `json:"maxNumBatch"` // uint32
82
83 // FromIdx
84 FromIdx []*big.Int `json:"fromIdx"` // uint64 (max nLevels bits), len: [nTx]
85 // AuxFromIdx is the Idx of the new created account which is consequence of a L1CreateAccountTx
86 AuxFromIdx []*big.Int `json:"auxFromIdx"` // uint64 (max nLevels bits), len: [nTx]
87
88 // ToIdx
89 ToIdx []*big.Int `json:"toIdx"` // uint64 (max nLevels bits), len: [nTx]
90 // AuxToIdx is the Idx of the Tx that has 'toIdx==0', is the coordinator who will find which Idx corresponds to the 'toBJJAy' or 'toEthAddr'
91 AuxToIdx []*big.Int `json:"auxToIdx"` // uint64 (max nLevels bits), len: [nTx]
92 // ToBJJAy
93 ToBJJAy []*big.Int `json:"toBjjAy"` // big.Int, len: [nTx]
94 // ToEthAddr
95 ToEthAddr []*big.Int `json:"toEthAddr"` // ethCommon.Address, len: [nTx]
96
97 // OnChain determines if is L1 (1/true) or L2 (0/false)
98 OnChain []*big.Int `json:"onChain"` // bool, len: [nTx]
99
100 //
101 // Txs/L1Txs
102 //
103 // NewAccount boolean (0/1) flag set 'true' when L1 tx creates a new account (fromIdx==0)
104 NewAccount []*big.Int `json:"newAccount"` // bool, len: [nTx]
105 // LoadAmountF encoded as float16
106 LoadAmountF []*big.Int `json:"loadAmountF"` // uint16, len: [nTx]
107 // FromEthAddr
108 FromEthAddr []*big.Int `json:"fromEthAddr"` // ethCommon.Address, len: [nTx]
109 // FromBJJCompressed boolean encoded where each value is a *big.Int
110 FromBJJCompressed [][256]*big.Int `json:"fromBjjCompressed"` // bool array, len: [nTx][256]
111
112 //
113 // Txs/L2Txs
114 //
115
116 // RqOffset relative transaction position to be linked. Used to perform atomic transactions.
117 RqOffset []*big.Int `json:"rqOffset"` // uint8 (max 3 bits), len: [nTx]
118
119 // transaction L2 request data
120 // RqTxCompressedDataV2
121 RqTxCompressedDataV2 []*big.Int `json:"rqTxCompressedDataV2"` // big.Int (max 251 bits), len: [nTx]
122 // RqToEthAddr
123 RqToEthAddr []*big.Int `json:"rqToEthAddr"` // ethCommon.Address, len: [nTx]
124 // RqToBJJAy
125 RqToBJJAy []*big.Int `json:"rqToBjjAy"` // big.Int, len: [nTx]
126
127 // transaction L2 signature
128 // S
129 S []*big.Int `json:"s"` // big.Int, len: [nTx]
130 // R8x
131 R8x []*big.Int `json:"r8x"` // big.Int, len: [nTx]
132 // R8y
133 R8y []*big.Int `json:"r8y"` // big.Int, len: [nTx]
134
135 //
136 // State MerkleTree Leafs transitions
137 //
138
139 // state 1, value of the sender (from) account leaf
140 TokenID1 []*big.Int `json:"tokenID1"` // uint32, len: [nTx]
141 Nonce1 []*big.Int `json:"nonce1"` // uint64 (max 40 bits), len: [nTx]
142 Sign1 []*big.Int `json:"sign1"` // bool, len: [nTx]
143 Ay1 []*big.Int `json:"ay1"` // big.Int, len: [nTx]
144 Balance1 []*big.Int `json:"balance1"` // big.Int (max 192 bits), len: [nTx]
145 EthAddr1 []*big.Int `json:"ethAddr1"` // ethCommon.Address, len: [nTx]
146 Siblings1 [][]*big.Int `json:"siblings1"` // big.Int, len: [nTx][nLevels + 1]
147 // Required for inserts and deletes, values of the CircomProcessorProof (smt insert proof)
148 IsOld0_1 []*big.Int `json:"isOld0_1"` // bool, len: [nTx]
149 OldKey1 []*big.Int `json:"oldKey1"` // uint64 (max 40 bits), len: [nTx]
150 OldValue1 []*big.Int `json:"oldValue1"` // Hash, len: [nTx]
151
152 // state 2, value of the receiver (to) account leaf
153 // if Tx is an Exit, state 2 is used for the Exit Merkle Proof
154 TokenID2 []*big.Int `json:"tokenID2"` // uint32, len: [nTx]
155 Nonce2 []*big.Int `json:"nonce2"` // uint64 (max 40 bits), len: [nTx]
156 Sign2 []*big.Int `json:"sign2"` // bool, len: [nTx]
157 Ay2 []*big.Int `json:"ay2"` // big.Int, len: [nTx]
158 Balance2 []*big.Int `json:"balance2"` // big.Int (max 192 bits), len: [nTx]
159 EthAddr2 []*big.Int `json:"ethAddr2"` // ethCommon.Address, len: [nTx]
160 Siblings2 [][]*big.Int `json:"siblings2"` // big.Int, len: [nTx][nLevels + 1]
161 // newExit determines if an exit transaction has to create a new leaf in the exit tree
162 NewExit []*big.Int `json:"newExit"` // bool, len: [nTx]
163 // Required for inserts and deletes, values of the CircomProcessorProof (smt insert proof)
164 IsOld0_2 []*big.Int `json:"isOld0_2"` // bool, len: [nTx]
165 OldKey2 []*big.Int `json:"oldKey2"` // uint64 (max 40 bits), len: [nTx]
166 OldValue2 []*big.Int `json:"oldValue2"` // Hash, len: [nTx]
167
168 // state 3, value of the account leaf receiver of the Fees
169 // fee tx
170 // State fees
171 TokenID3 []*big.Int `json:"tokenID3"` // uint32, len: [maxFeeIdxs]
172 Nonce3 []*big.Int `json:"nonce3"` // uint64 (max 40 bits), len: [maxFeeIdxs]
173 Sign3 []*big.Int `json:"sign3"` // bool, len: [maxFeeIdxs]
174 Ay3 []*big.Int `json:"ay3"` // big.Int, len: [maxFeeIdxs]
175 Balance3 []*big.Int `json:"balance3"` // big.Int (max 192 bits), len: [maxFeeIdxs]
176 EthAddr3 []*big.Int `json:"ethAddr3"` // ethCommon.Address, len: [maxFeeIdxs]
177 Siblings3 [][]*big.Int `json:"siblings3"` // Hash, len: [maxFeeIdxs][nLevels + 1]
178
179 //
180 // Intermediate States
181 //
182
183 // Intermediate States to parallelize witness computation
184 // Note: the Intermediate States (IS) of the last transaction does not
185 // exist. Meaning that transaction 3 (4th) will fill the parameters
186 // FromIdx[3] and ISOnChain[3], but last transaction (nTx-1) will fill
187 // FromIdx[nTx-1] but will not fill ISOnChain. That's why IS have
188 // length of nTx-1, while the other parameters have length of nTx.
189 // Last transaction does not need intermediate state since its output
190 // will not be used.
191
192 // decode-tx
193 // ISOnChain indicates if tx is L1 (true (1)) or L2 (false (0))
194 ISOnChain []*big.Int `json:"imOnChain"` // bool, len: [nTx - 1]
195 // ISOutIdx current index account for each Tx
196 // Contains the index of the created account in case that the tx is of
197 // account creation type.
198 ISOutIdx []*big.Int `json:"imOutIdx"` // uint64 (max nLevels bits), len: [nTx - 1]
199 // rollup-tx
200 // ISStateRoot root at the moment of the Tx (once processed), the state root value once the Tx is processed into the state tree
201 ISStateRoot []*big.Int `json:"imStateRoot"` // Hash, len: [nTx - 1]
202 // ISExitTree root at the moment (once processed) of the Tx the value
203 // once the Tx is processed into the exit tree
204 ISExitRoot []*big.Int `json:"imExitRoot"` // Hash, len: [nTx - 1]
205 // ISAccFeeOut accumulated fees once the Tx is processed. Contains the
206 // array of FeeAccount Balances at each moment of each Tx processed.
207 ISAccFeeOut [][]*big.Int `json:"imAccFeeOut"` // big.Int, len: [nTx - 1][maxFeeIdxs]
208 // fee-tx
209 // ISStateRootFee root at the moment of the Tx (once processed), the state root value once the Tx is processed into the state tree
210 ISStateRootFee []*big.Int `json:"imStateRootFee"` // Hash, len: [maxFeeIdxs - 1]
211 // ISInitStateRootFee state root once all L1-L2 tx are processed (before computing the fees-tx)
212 ISInitStateRootFee *big.Int `json:"imInitStateRootFee"` // Hash
213 // ISFinalAccFee final accumulated fees (before computing the fees-tx).
214 // Contains the final values of the ISAccFeeOut parameter
215 ISFinalAccFee []*big.Int `json:"imFinalAccFee"` // big.Int, len: [maxFeeIdxs - 1]
216}
217
218func bigIntsToStrings(v interface{}) interface{} {
219 switch c := v.(type) {
220 case *big.Int:
221 return c.String()
222 case []*big.Int:
223 r := make([]interface{}, len(c))
224 for i := range c {
225 r[i] = bigIntsToStrings(c[i])
226 }
227 return r
228 case [256]*big.Int:
229 r := make([]interface{}, len(c))
230 for i := range c {
231 r[i] = bigIntsToStrings(c[i])
232 }
233 return r
234 case [][]*big.Int:
235 r := make([]interface{}, len(c))
236 for i := range c {
237 r[i] = bigIntsToStrings(c[i])
238 }
239 return r
240 case [][256]*big.Int:
241 r := make([]interface{}, len(c))
242 for i := range c {
243 r[i] = bigIntsToStrings(c[i])
244 }
245 return r
246 case map[string]interface{}:
247 // avoid printing a warning when there is a struct type
248 default:
249 log.Warnf("bigIntsToStrings unexpected type: %T\n", v)
250 }
251 return nil
252}
253
254// MarshalJSON implements the json marshaler for ZKInputs
255func (z ZKInputs) MarshalJSON() ([]byte, error) {
256 var m map[string]interface{}
257 dec, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
258 TagName: "json",
259 Result: &m,
260 })
261 if err != nil {
262 return nil, tracerr.Wrap(err)
263 }
264 err = dec.Decode(z)
265 if err != nil {
266 return nil, tracerr.Wrap(err)
267 }
268
269 for k, v := range m {
270 m[k] = bigIntsToStrings(v)
271 }
272 return json.Marshal(m)
273}
274
275// NewZKInputs returns a pointer to an initialized struct of ZKInputs
276func NewZKInputs(nTx, maxL1Tx, maxTx, maxFeeIdxs, nLevels uint32, currentNumBatch *big.Int) *ZKInputs {
277 zki := &ZKInputs{}
278 zki.Metadata.NTx = nTx
279 zki.Metadata.MaxFeeIdxs = maxFeeIdxs
280 zki.Metadata.NLevels = nLevels
281 zki.Metadata.MaxLevels = uint32(48) //nolint:gomnd
282 zki.Metadata.MaxL1Tx = maxL1Tx
283 zki.Metadata.MaxTx = maxTx
284
285 // General
286 zki.CurrentNumBatch = currentNumBatch
287 zki.OldLastIdx = big.NewInt(0)
288 zki.OldStateRoot = big.NewInt(0)
289 zki.GlobalChainID = big.NewInt(0) // TODO pass by parameter
290 zki.FeeIdxs = newSlice(maxFeeIdxs)
291 zki.FeePlanTokens = newSlice(maxFeeIdxs)
292
293 // Txs
294 zki.TxCompressedData = newSlice(nTx)
295 zki.TxCompressedDataV2 = newSlice(nTx)
296 zki.MaxNumBatch = newSlice(nTx)
297 zki.FromIdx = newSlice(nTx)
298 zki.AuxFromIdx = newSlice(nTx)
299 zki.ToIdx = newSlice(nTx)
300 zki.AuxToIdx = newSlice(nTx)
301 zki.ToBJJAy = newSlice(nTx)
302 zki.ToEthAddr = newSlice(nTx)
303 zki.OnChain = newSlice(nTx)
304 zki.NewAccount = newSlice(nTx)
305
306 // L1
307 zki.LoadAmountF = newSlice(nTx)
308 zki.FromEthAddr = newSlice(nTx)
309 zki.FromBJJCompressed = make([][256]*big.Int, nTx)
310 for i := 0; i < len(zki.FromBJJCompressed); i++ {
311 // zki.FromBJJCompressed[i] = newSlice(256)
312 for j := 0; j < 256; j++ {
313 zki.FromBJJCompressed[i][j] = big.NewInt(0)
314 }
315 }
316
317 // L2
318 zki.RqOffset = newSlice(nTx)
319 zki.RqTxCompressedDataV2 = newSlice(nTx)
320 zki.RqToEthAddr = newSlice(nTx)
321 zki.RqToBJJAy = newSlice(nTx)
322 zki.S = newSlice(nTx)
323 zki.R8x = newSlice(nTx)
324 zki.R8y = newSlice(nTx)
325
326 // State MerkleTree Leafs transitions
327 zki.TokenID1 = newSlice(nTx)
328 zki.Nonce1 = newSlice(nTx)
329 zki.Sign1 = newSlice(nTx)
330 zki.Ay1 = newSlice(nTx)
331 zki.Balance1 = newSlice(nTx)
332 zki.EthAddr1 = newSlice(nTx)
333 zki.Siblings1 = make([][]*big.Int, nTx)
334 for i := 0; i < len(zki.Siblings1); i++ {
335 zki.Siblings1[i] = newSlice(nLevels + 1)
336 }
337 zki.IsOld0_1 = newSlice(nTx)
338 zki.OldKey1 = newSlice(nTx)
339 zki.OldValue1 = newSlice(nTx)
340
341 zki.TokenID2 = newSlice(nTx)
342 zki.Nonce2 = newSlice(nTx)
343 zki.Sign2 = newSlice(nTx)
344 zki.Ay2 = newSlice(nTx)
345 zki.Balance2 = newSlice(nTx)
346 zki.EthAddr2 = newSlice(nTx)
347 zki.Siblings2 = make([][]*big.Int, nTx)
348 for i := 0; i < len(zki.Siblings2); i++ {
349 zki.Siblings2[i] = newSlice(nLevels + 1)
350 }
351 zki.NewExit = newSlice(nTx)
352 zki.IsOld0_2 = newSlice(nTx)
353 zki.OldKey2 = newSlice(nTx)
354 zki.OldValue2 = newSlice(nTx)
355
356 zki.TokenID3 = newSlice(maxFeeIdxs)
357 zki.Nonce3 = newSlice(maxFeeIdxs)
358 zki.Sign3 = newSlice(maxFeeIdxs)
359 zki.Ay3 = newSlice(maxFeeIdxs)
360 zki.Balance3 = newSlice(maxFeeIdxs)
361 zki.EthAddr3 = newSlice(maxFeeIdxs)
362 zki.Siblings3 = make([][]*big.Int, maxFeeIdxs)
363 for i := 0; i < len(zki.Siblings3); i++ {
364 zki.Siblings3[i] = newSlice(nLevels + 1)
365 }
366
367 // Intermediate States
368 zki.ISOnChain = newSlice(nTx - 1)
369 zki.ISOutIdx = newSlice(nTx - 1)
370 zki.ISStateRoot = newSlice(nTx - 1)
371 zki.ISExitRoot = newSlice(nTx - 1)
372 zki.ISAccFeeOut = make([][]*big.Int, nTx-1)
373 for i := 0; i < len(zki.ISAccFeeOut); i++ {
374 zki.ISAccFeeOut[i] = newSlice(maxFeeIdxs)
375 }
376 zki.ISStateRootFee = newSlice(maxFeeIdxs - 1)
377 zki.ISInitStateRootFee = big.NewInt(0)
378 zki.ISFinalAccFee = newSlice(maxFeeIdxs - 1)
379
380 return zki
381}
382
383// newSlice returns a []*big.Int slice of length n with values initialized at
384// 0.
385// Is used to initialize all *big.Ints of the ZKInputs data structure, so when
386// the transactions are processed and the ZKInputs filled, there is no need to
387// set all the elements, and if a transaction does not use a parameter, can be
388// leaved as it is in the ZKInputs, as will be 0, so later when using the
389// ZKInputs to generate the zkSnark proof there is no 'nil'/'null' values.
390func newSlice(n uint32) []*big.Int {
391 s := make([]*big.Int, n)
392 for i := 0; i < len(s); i++ {
393 s[i] = big.NewInt(0)
394 }
395 return s
396}
397
398// HashGlobalData returns the HashGlobalData
399func (z ZKInputs) HashGlobalData() (*big.Int, error) {
400 b, err := z.ToHashGlobalData()
401 if err != nil {
402 return nil, tracerr.Wrap(err)
403 }
404
405 h := sha256.New()
406 _, err = h.Write(b)
407 if err != nil {
408 return nil, tracerr.Wrap(err)
409 }
410
411 r := new(big.Int).SetBytes(h.Sum(nil))
412 v := r.Mod(r, cryptoConstants.Q)
413
414 return v, nil
415}
416
417// ToHashGlobalData returns the data to be hashed in the method HashGlobalData
418func (z ZKInputs) ToHashGlobalData() ([]byte, error) {
419 var b []byte
420 bytesMaxLevels := int(z.Metadata.MaxLevels / 8) //nolint:gomnd
421
422 // [MAX_NLEVELS bits] oldLastIdx
423 oldLastIdx := make([]byte, bytesMaxLevels)
424 copy(oldLastIdx, z.OldLastIdx.Bytes())
425 b = append(b, SwapEndianness(oldLastIdx)...)
426
427 // [MAX_NLEVELS bits] newLastIdx
428 newLastIdx := make([]byte, bytesMaxLevels)
429 newLastIdxBytes, err := z.Metadata.NewLastIdxRaw.Bytes()
430 if err != nil {
431 return nil, tracerr.Wrap(err)
432 }
433 copy(newLastIdx, newLastIdxBytes[len(newLastIdxBytes)-bytesMaxLevels:])
434 b = append(b, newLastIdx...)
435
436 // [256 bits] oldStRoot
437 oldStateRoot := make([]byte, 32)
438 copy(oldStateRoot, z.OldStateRoot.Bytes())
439 b = append(b, oldStateRoot...)
440
441 // [256 bits] newStateRoot
442 newStateRoot := make([]byte, 32)
443 copy(newStateRoot, z.Metadata.NewStateRootRaw.Bytes())
444 b = append(b, newStateRoot...)
445
446 // [256 bits] newExitRoot
447 newExitRoot := make([]byte, 32)
448 copy(newExitRoot, z.Metadata.NewExitRootRaw.Bytes())
449 b = append(b, newExitRoot...)
450
451 // [MAX_L1_TX * (2 * MAX_NLEVELS + 480) bits] L1TxsData
452 l1TxDataLen := (2*z.Metadata.MaxLevels + 480)
453 l1TxsDataLen := (z.Metadata.MaxL1Tx * l1TxDataLen)
454 l1TxsData := make([]byte, l1TxsDataLen/8) //nolint:gomnd
455 for i := 0; i < len(z.Metadata.L1TxsData); i++ {
456 dataLen := int(l1TxDataLen) / 8 //nolint:gomnd
457 pos0 := i * dataLen
458 pos1 := i*dataLen + dataLen
459 copy(l1TxsData[pos0:pos1], z.Metadata.L1TxsData[i])
460 }
461 b = append(b, l1TxsData...)
462
463 var l1TxsDataAvailability []byte
464 for i := 0; i < len(z.Metadata.L1TxsDataAvailability); i++ {
465 l1TxsDataAvailability = append(l1TxsDataAvailability, z.Metadata.L1TxsDataAvailability[i]...)
466 }
467 b = append(b, l1TxsDataAvailability...)
468
469 // [MAX_TX*(2*NLevels + 24) bits] L2TxsData
470 var l2TxsData []byte
471 l2TxDataLen := 2*z.Metadata.NLevels + 24 //nolint:gomnd
472 l2TxsDataLen := (z.Metadata.MaxTx * l2TxDataLen)
473 expectedL2TxsDataLen := l2TxsDataLen / 8 //nolint:gomnd
474 for i := 0; i < len(z.Metadata.L2TxsData); i++ {
475 l2TxsData = append(l2TxsData, z.Metadata.L2TxsData[i]...)
476 }
477 if len(l2TxsData) > int(expectedL2TxsDataLen) {
478 return nil, tracerr.Wrap(fmt.Errorf("len(l2TxsData): %d, expected: %d", len(l2TxsData), expectedL2TxsDataLen))
479 }
480
481 b = append(b, l2TxsData...)
482 l2TxsPadding := make([]byte, (int(z.Metadata.MaxTx)-len(z.Metadata.L1TxsDataAvailability)-len(z.Metadata.L2TxsData))*int(l2TxDataLen)/8) //nolint:gomnd
483 b = append(b, l2TxsPadding...)
484
485 // [NLevels * MAX_TOKENS_FEE bits] feeTxsData
486 for i := 0; i < len(z.FeeIdxs); i++ {
487 var r []byte
488
489 padding := make([]byte, bytesMaxLevels/4) //nolint:gomnd
490 r = append(r, padding...)
491
492 feeIdx := make([]byte, bytesMaxLevels/2) //nolint:gomnd
493 feeIdxBytes := z.FeeIdxs[i].Bytes()
494 copy(feeIdx[len(feeIdx)-len(feeIdxBytes):], feeIdxBytes[:])
495 r = append(r, feeIdx...)
496 b = append(b, r...)
497 }
498
499 // [16 bits] chainID
500 var chainID [2]byte
501 binary.BigEndian.PutUint16(chainID[:], z.Metadata.ChainID)
502 b = append(b, chainID[:]...)
503
504 // [32 bits] currentNumBatch
505 currNumBatchBytes := z.CurrentNumBatch.Bytes()
506 var currNumBatch [4]byte
507 copy(currNumBatch[4-len(currNumBatchBytes):], currNumBatchBytes)
508 b = append(b, currNumBatch[:]...)
509
510 return b, nil
511}