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
62 // value can be get from the smart contract.
63 GlobalChainID *big.Int `json:"globalChainID"` // uint16
64 // FeeIdxs is an array of merkle tree indexes where the coordinator
65 // will receive the accumulated fees
66 FeeIdxs []*big.Int `json:"feeIdxs"` // uint64 (max nLevels bits), len: [maxFeeIdxs]
67
68 // accumulate fees
69 // FeePlanTokens contains all the tokenIDs for which the fees are being accumulated
70 FeePlanTokens []*big.Int `json:"feePlanTokens"` // uint32 (max nLevels bits), len: [maxFeeIdxs]
71
72 //
73 // Txs (L1&L2)
74 //
75
76 // transaction L1-L2
77 // TxCompressedData
78 TxCompressedData []*big.Int `json:"txCompressedData"` // big.Int (max 251 bits), len: [nTx]
79 // TxCompressedDataV2, only used in L2Txs, in L1Txs is set to 0
80 TxCompressedDataV2 []*big.Int `json:"txCompressedDataV2"` // big.Int (max 193 bits), len: [nTx]
81 // MaxNumBatch is the maximum allowed batch number when the transaction
82 // can be processed
83 MaxNumBatch []*big.Int `json:"maxNumBatch"` // uint32
84
85 // FromIdx
86 FromIdx []*big.Int `json:"fromIdx"` // uint64 (max nLevels bits), len: [nTx]
87 // AuxFromIdx is the Idx of the new created account which is consequence of a L1CreateAccountTx
88 AuxFromIdx []*big.Int `json:"auxFromIdx"` // uint64 (max nLevels bits), len: [nTx]
89
90 // ToIdx
91 ToIdx []*big.Int `json:"toIdx"` // uint64 (max nLevels bits), len: [nTx]
92 // AuxToIdx is the Idx of the Tx that has 'toIdx==0', is the
93 // coordinator who will find which Idx corresponds to the 'toBJJAy' or
94 // 'toEthAddr'
95 AuxToIdx []*big.Int `json:"auxToIdx"` // uint64 (max nLevels bits), len: [nTx]
96 // ToBJJAy
97 ToBJJAy []*big.Int `json:"toBjjAy"` // big.Int, len: [nTx]
98 // ToEthAddr
99 ToEthAddr []*big.Int `json:"toEthAddr"` // ethCommon.Address, len: [nTx]
100
101 // OnChain determines if is L1 (1/true) or L2 (0/false)
102 OnChain []*big.Int `json:"onChain"` // bool, len: [nTx]
103
104 //
105 // Txs/L1Txs
106 //
107 // NewAccount boolean (0/1) flag set 'true' when L1 tx creates a new account (fromIdx==0)
108 NewAccount []*big.Int `json:"newAccount"` // bool, len: [nTx]
109 // DepositAmountF encoded as float16
110 DepositAmountF []*big.Int `json:"loadAmountF"` // uint16, len: [nTx]
111 // FromEthAddr
112 FromEthAddr []*big.Int `json:"fromEthAddr"` // ethCommon.Address, len: [nTx]
113 // FromBJJCompressed boolean encoded where each value is a *big.Int
114 FromBJJCompressed [][256]*big.Int `json:"fromBjjCompressed"` // bool array, len: [nTx][256]
115
116 //
117 // Txs/L2Txs
118 //
119
120 // RqOffset relative transaction position to be linked. Used to perform atomic transactions.
121 RqOffset []*big.Int `json:"rqOffset"` // uint8 (max 3 bits), len: [nTx]
122
123 // transaction L2 request data
124 // RqTxCompressedDataV2
125 RqTxCompressedDataV2 []*big.Int `json:"rqTxCompressedDataV2"` // big.Int (max 251 bits), len: [nTx]
126 // RqToEthAddr
127 RqToEthAddr []*big.Int `json:"rqToEthAddr"` // ethCommon.Address, len: [nTx]
128 // RqToBJJAy
129 RqToBJJAy []*big.Int `json:"rqToBjjAy"` // big.Int, len: [nTx]
130
131 // transaction L2 signature
132 // S
133 S []*big.Int `json:"s"` // big.Int, len: [nTx]
134 // R8x
135 R8x []*big.Int `json:"r8x"` // big.Int, len: [nTx]
136 // R8y
137 R8y []*big.Int `json:"r8y"` // big.Int, len: [nTx]
138
139 //
140 // State MerkleTree Leafs transitions
141 //
142
143 // state 1, value of the sender (from) account leaf. The values at the
144 // moment pre-smtprocessor of the update (before updating the Sender
145 // leaf).
146 TokenID1 []*big.Int `json:"tokenID1"` // uint32, len: [nTx]
147 Nonce1 []*big.Int `json:"nonce1"` // uint64 (max 40 bits), len: [nTx]
148 Sign1 []*big.Int `json:"sign1"` // bool, len: [nTx]
149 Ay1 []*big.Int `json:"ay1"` // big.Int, len: [nTx]
150 Balance1 []*big.Int `json:"balance1"` // big.Int (max 192 bits), len: [nTx]
151 EthAddr1 []*big.Int `json:"ethAddr1"` // ethCommon.Address, len: [nTx]
152 Siblings1 [][]*big.Int `json:"siblings1"` // big.Int, len: [nTx][nLevels + 1]
153 // Required for inserts and deletes, values of the CircomProcessorProof (smt insert proof)
154 IsOld0_1 []*big.Int `json:"isOld0_1"` // bool, len: [nTx]
155 OldKey1 []*big.Int `json:"oldKey1"` // uint64 (max 40 bits), len: [nTx]
156 OldValue1 []*big.Int `json:"oldValue1"` // Hash, len: [nTx]
157
158 // state 2, value of the receiver (to) account leaf
159 // if Tx is an Exit, state 2 is used for the Exit Merkle Proof
160 TokenID2 []*big.Int `json:"tokenID2"` // uint32, len: [nTx]
161 Nonce2 []*big.Int `json:"nonce2"` // uint64 (max 40 bits), len: [nTx]
162 Sign2 []*big.Int `json:"sign2"` // bool, len: [nTx]
163 Ay2 []*big.Int `json:"ay2"` // big.Int, len: [nTx]
164 Balance2 []*big.Int `json:"balance2"` // big.Int (max 192 bits), len: [nTx]
165 EthAddr2 []*big.Int `json:"ethAddr2"` // ethCommon.Address, len: [nTx]
166 Siblings2 [][]*big.Int `json:"siblings2"` // big.Int, len: [nTx][nLevels + 1]
167 // newExit determines if an exit transaction has to create a new leaf in the exit tree
168 NewExit []*big.Int `json:"newExit"` // bool, len: [nTx]
169 // Required for inserts and deletes, values of the CircomProcessorProof (smt insert proof)
170 IsOld0_2 []*big.Int `json:"isOld0_2"` // bool, len: [nTx]
171 OldKey2 []*big.Int `json:"oldKey2"` // uint64 (max 40 bits), len: [nTx]
172 OldValue2 []*big.Int `json:"oldValue2"` // Hash, len: [nTx]
173
174 // state 3, value of the account leaf receiver of the Fees
175 // fee tx
176 // State fees
177 TokenID3 []*big.Int `json:"tokenID3"` // uint32, len: [maxFeeIdxs]
178 Nonce3 []*big.Int `json:"nonce3"` // uint64 (max 40 bits), len: [maxFeeIdxs]
179 Sign3 []*big.Int `json:"sign3"` // bool, len: [maxFeeIdxs]
180 Ay3 []*big.Int `json:"ay3"` // big.Int, len: [maxFeeIdxs]
181 Balance3 []*big.Int `json:"balance3"` // big.Int (max 192 bits), len: [maxFeeIdxs]
182 EthAddr3 []*big.Int `json:"ethAddr3"` // ethCommon.Address, len: [maxFeeIdxs]
183 Siblings3 [][]*big.Int `json:"siblings3"` // Hash, len: [maxFeeIdxs][nLevels + 1]
184
185 //
186 // Intermediate States
187 //
188
189 // Intermediate States to parallelize witness computation
190 // Note: the Intermediate States (IS) of the last transaction does not
191 // exist. Meaning that transaction 3 (4th) will fill the parameters
192 // FromIdx[3] and ISOnChain[3], but last transaction (nTx-1) will fill
193 // FromIdx[nTx-1] but will not fill ISOnChain. That's why IS have
194 // length of nTx-1, while the other parameters have length of nTx.
195 // Last transaction does not need intermediate state since its output
196 // will not be used.
197
198 // decode-tx
199 // ISOnChain indicates if tx is L1 (true (1)) or L2 (false (0))
200 ISOnChain []*big.Int `json:"imOnChain"` // bool, len: [nTx - 1]
201 // ISOutIdx current index account for each Tx
202 // Contains the index of the created account in case that the tx is of
203 // account creation type.
204 ISOutIdx []*big.Int `json:"imOutIdx"` // uint64 (max nLevels bits), len: [nTx - 1]
205 // rollup-tx
206 // ISStateRoot root at the moment of the Tx (once processed), the state root value once the Tx is processed into the state tree
207 ISStateRoot []*big.Int `json:"imStateRoot"` // Hash, len: [nTx - 1]
208 // ISExitTree root at the moment (once processed) of the Tx the value
209 // once the Tx is processed into the exit tree
210 ISExitRoot []*big.Int `json:"imExitRoot"` // Hash, len: [nTx - 1]
211 // ISAccFeeOut accumulated fees once the Tx is processed. Contains the
212 // array of FeeAccount Balances at each moment of each Tx processed.
213 ISAccFeeOut [][]*big.Int `json:"imAccFeeOut"` // big.Int, len: [nTx - 1][maxFeeIdxs]
214 // fee-tx
215 // ISStateRootFee root at the moment of the Tx (once processed), the state root value once the Tx is processed into the state tree
216 ISStateRootFee []*big.Int `json:"imStateRootFee"` // Hash, len: [maxFeeIdxs - 1]
217 // ISInitStateRootFee state root once all L1-L2 tx are processed (before computing the fees-tx)
218 ISInitStateRootFee *big.Int `json:"imInitStateRootFee"` // Hash
219 // ISFinalAccFee final accumulated fees (before computing the fees-tx).
220 // Contains the final values of the ISAccFeeOut parameter
221 ISFinalAccFee []*big.Int `json:"imFinalAccFee"` // big.Int, len: [maxFeeIdxs - 1]
222}
223
224func bigIntsToStrings(v interface{}) interface{} {
225 switch c := v.(type) {
226 case *big.Int:
227 return c.String()
228 case []*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 [256]*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 [][]*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 [][256]*big.Int:
247 r := make([]interface{}, len(c))
248 for i := range c {
249 r[i] = bigIntsToStrings(c[i])
250 }
251 return r
252 case map[string]interface{}:
253 // avoid printing a warning when there is a struct type
254 default:
255 log.Warnf("bigIntsToStrings unexpected type: %T\n", v)
256 }
257 return nil
258}
259
260// MarshalJSON implements the json marshaler for ZKInputs
261func (z ZKInputs) MarshalJSON() ([]byte, error) {
262 var m map[string]interface{}
263 dec, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
264 TagName: "json",
265 Result: &m,
266 })
267 if err != nil {
268 return nil, tracerr.Wrap(err)
269 }
270 err = dec.Decode(z)
271 if err != nil {
272 return nil, tracerr.Wrap(err)
273 }
274
275 for k, v := range m {
276 m[k] = bigIntsToStrings(v)
277 }
278 return json.Marshal(m)
279}
280
281// NewZKInputs returns a pointer to an initialized struct of ZKInputs
282func NewZKInputs(nTx, maxL1Tx, maxTx, maxFeeIdxs, nLevels uint32, currentNumBatch *big.Int) *ZKInputs {
283 zki := &ZKInputs{}
284 zki.Metadata.NTx = nTx
285 zki.Metadata.MaxFeeIdxs = maxFeeIdxs
286 zki.Metadata.NLevels = nLevels
287 zki.Metadata.MaxLevels = uint32(48) //nolint:gomnd
288 zki.Metadata.MaxL1Tx = maxL1Tx
289 zki.Metadata.MaxTx = maxTx
290
291 // General
292 zki.CurrentNumBatch = currentNumBatch
293 zki.OldLastIdx = big.NewInt(0)
294 zki.OldStateRoot = big.NewInt(0)
295 zki.GlobalChainID = big.NewInt(0) // TODO pass by parameter
296 zki.FeeIdxs = newSlice(maxFeeIdxs)
297 zki.FeePlanTokens = newSlice(maxFeeIdxs)
298
299 // Txs
300 zki.TxCompressedData = newSlice(nTx)
301 zki.TxCompressedDataV2 = newSlice(nTx)
302 zki.MaxNumBatch = newSlice(nTx)
303 zki.FromIdx = newSlice(nTx)
304 zki.AuxFromIdx = newSlice(nTx)
305 zki.ToIdx = newSlice(nTx)
306 zki.AuxToIdx = newSlice(nTx)
307 zki.ToBJJAy = newSlice(nTx)
308 zki.ToEthAddr = newSlice(nTx)
309 zki.OnChain = newSlice(nTx)
310 zki.NewAccount = newSlice(nTx)
311
312 // L1
313 zki.DepositAmountF = newSlice(nTx)
314 zki.FromEthAddr = newSlice(nTx)
315 zki.FromBJJCompressed = make([][256]*big.Int, nTx)
316 for i := 0; i < len(zki.FromBJJCompressed); i++ {
317 // zki.FromBJJCompressed[i] = newSlice(256)
318 for j := 0; j < 256; j++ {
319 zki.FromBJJCompressed[i][j] = big.NewInt(0)
320 }
321 }
322
323 // L2
324 zki.RqOffset = newSlice(nTx)
325 zki.RqTxCompressedDataV2 = newSlice(nTx)
326 zki.RqToEthAddr = newSlice(nTx)
327 zki.RqToBJJAy = newSlice(nTx)
328 zki.S = newSlice(nTx)
329 zki.R8x = newSlice(nTx)
330 zki.R8y = newSlice(nTx)
331
332 // State MerkleTree Leafs transitions
333 zki.TokenID1 = newSlice(nTx)
334 zki.Nonce1 = newSlice(nTx)
335 zki.Sign1 = newSlice(nTx)
336 zki.Ay1 = newSlice(nTx)
337 zki.Balance1 = newSlice(nTx)
338 zki.EthAddr1 = newSlice(nTx)
339 zki.Siblings1 = make([][]*big.Int, nTx)
340 for i := 0; i < len(zki.Siblings1); i++ {
341 zki.Siblings1[i] = newSlice(nLevels + 1)
342 }
343 zki.IsOld0_1 = newSlice(nTx)
344 zki.OldKey1 = newSlice(nTx)
345 zki.OldValue1 = newSlice(nTx)
346
347 zki.TokenID2 = newSlice(nTx)
348 zki.Nonce2 = newSlice(nTx)
349 zki.Sign2 = newSlice(nTx)
350 zki.Ay2 = newSlice(nTx)
351 zki.Balance2 = newSlice(nTx)
352 zki.EthAddr2 = newSlice(nTx)
353 zki.Siblings2 = make([][]*big.Int, nTx)
354 for i := 0; i < len(zki.Siblings2); i++ {
355 zki.Siblings2[i] = newSlice(nLevels + 1)
356 }
357 zki.NewExit = newSlice(nTx)
358 zki.IsOld0_2 = newSlice(nTx)
359 zki.OldKey2 = newSlice(nTx)
360 zki.OldValue2 = newSlice(nTx)
361
362 zki.TokenID3 = newSlice(maxFeeIdxs)
363 zki.Nonce3 = newSlice(maxFeeIdxs)
364 zki.Sign3 = newSlice(maxFeeIdxs)
365 zki.Ay3 = newSlice(maxFeeIdxs)
366 zki.Balance3 = newSlice(maxFeeIdxs)
367 zki.EthAddr3 = newSlice(maxFeeIdxs)
368 zki.Siblings3 = make([][]*big.Int, maxFeeIdxs)
369 for i := 0; i < len(zki.Siblings3); i++ {
370 zki.Siblings3[i] = newSlice(nLevels + 1)
371 }
372
373 // Intermediate States
374 zki.ISOnChain = newSlice(nTx - 1)
375 zki.ISOutIdx = newSlice(nTx - 1)
376 zki.ISStateRoot = newSlice(nTx - 1)
377 zki.ISExitRoot = newSlice(nTx - 1)
378 zki.ISAccFeeOut = make([][]*big.Int, nTx-1)
379 for i := 0; i < len(zki.ISAccFeeOut); i++ {
380 zki.ISAccFeeOut[i] = newSlice(maxFeeIdxs)
381 }
382 zki.ISStateRootFee = newSlice(maxFeeIdxs - 1)
383 zki.ISInitStateRootFee = big.NewInt(0)
384 zki.ISFinalAccFee = newSlice(maxFeeIdxs - 1)
385
386 return zki
387}
388
389// newSlice returns a []*big.Int slice of length n with values initialized at
390// 0.
391// Is used to initialize all *big.Ints of the ZKInputs data structure, so when
392// the transactions are processed and the ZKInputs filled, there is no need to
393// set all the elements, and if a transaction does not use a parameter, can be
394// leaved as it is in the ZKInputs, as will be 0, so later when using the
395// ZKInputs to generate the zkSnark proof there is no 'nil'/'null' values.
396func newSlice(n uint32) []*big.Int {
397 s := make([]*big.Int, n)
398 for i := 0; i < len(s); i++ {
399 s[i] = big.NewInt(0)
400 }
401 return s
402}
403
404// HashGlobalData returns the HashGlobalData
405func (z ZKInputs) HashGlobalData() (*big.Int, error) {
406 b, err := z.ToHashGlobalData()
407 if err != nil {
408 return nil, tracerr.Wrap(err)
409 }
410
411 h := sha256.New()
412 _, err = h.Write(b)
413 if err != nil {
414 return nil, tracerr.Wrap(err)
415 }
416
417 r := new(big.Int).SetBytes(h.Sum(nil))
418 v := r.Mod(r, cryptoConstants.Q)
419
420 return v, nil
421}
422
423// ToHashGlobalData returns the data to be hashed in the method HashGlobalData
424func (z ZKInputs) ToHashGlobalData() ([]byte, error) {
425 var b []byte
426 bytesMaxLevels := int(z.Metadata.MaxLevels / 8) //nolint:gomnd
427
428 // [MAX_NLEVELS bits] oldLastIdx
429 oldLastIdx := make([]byte, bytesMaxLevels)
430 copy(oldLastIdx, z.OldLastIdx.Bytes())
431 b = append(b, SwapEndianness(oldLastIdx)...)
432
433 // [MAX_NLEVELS bits] newLastIdx
434 newLastIdx := make([]byte, bytesMaxLevels)
435 newLastIdxBytes, err := z.Metadata.NewLastIdxRaw.Bytes()
436 if err != nil {
437 return nil, tracerr.Wrap(err)
438 }
439 copy(newLastIdx, newLastIdxBytes[len(newLastIdxBytes)-bytesMaxLevels:])
440 b = append(b, newLastIdx...)
441
442 // [256 bits] oldStRoot
443 oldStateRoot := make([]byte, 32)
444 copy(oldStateRoot, z.OldStateRoot.Bytes())
445 b = append(b, oldStateRoot...)
446
447 // [256 bits] newStateRoot
448 newStateRoot := make([]byte, 32)
449 copy(newStateRoot, z.Metadata.NewStateRootRaw.Bytes())
450 b = append(b, newStateRoot...)
451
452 // [256 bits] newExitRoot
453 newExitRoot := make([]byte, 32)
454 copy(newExitRoot, z.Metadata.NewExitRootRaw.Bytes())
455 b = append(b, newExitRoot...)
456
457 // [MAX_L1_TX * (2 * MAX_NLEVELS + 480) bits] L1TxsData
458 l1TxDataLen := (2*z.Metadata.MaxLevels + 480)
459 l1TxsDataLen := (z.Metadata.MaxL1Tx * l1TxDataLen)
460 l1TxsData := make([]byte, l1TxsDataLen/8) //nolint:gomnd
461 for i := 0; i < len(z.Metadata.L1TxsData); i++ {
462 dataLen := int(l1TxDataLen) / 8 //nolint:gomnd
463 pos0 := i * dataLen
464 pos1 := i*dataLen + dataLen
465 copy(l1TxsData[pos0:pos1], z.Metadata.L1TxsData[i])
466 }
467 b = append(b, l1TxsData...)
468
469 var l1TxsDataAvailability []byte
470 for i := 0; i < len(z.Metadata.L1TxsDataAvailability); i++ {
471 l1TxsDataAvailability = append(l1TxsDataAvailability, z.Metadata.L1TxsDataAvailability[i]...)
472 }
473 b = append(b, l1TxsDataAvailability...)
474
475 // [MAX_TX*(2*NLevels + 24) bits] L2TxsData
476 var l2TxsData []byte
477 l2TxDataLen := 2*z.Metadata.NLevels + 24 //nolint:gomnd
478 l2TxsDataLen := (z.Metadata.MaxTx * l2TxDataLen)
479 expectedL2TxsDataLen := l2TxsDataLen / 8 //nolint:gomnd
480 for i := 0; i < len(z.Metadata.L2TxsData); i++ {
481 l2TxsData = append(l2TxsData, z.Metadata.L2TxsData[i]...)
482 }
483 if len(l2TxsData) > int(expectedL2TxsDataLen) {
484 return nil, tracerr.Wrap(fmt.Errorf("len(l2TxsData): %d, expected: %d", len(l2TxsData), expectedL2TxsDataLen))
485 }
486
487 b = append(b, l2TxsData...)
488 l2TxsPadding := make([]byte, (int(z.Metadata.MaxTx)-len(z.Metadata.L1TxsDataAvailability)-len(z.Metadata.L2TxsData))*int(l2TxDataLen)/8) //nolint:gomnd
489 b = append(b, l2TxsPadding...)
490
491 // [NLevels * MAX_TOKENS_FEE bits] feeTxsData
492 for i := 0; i < len(z.FeeIdxs); i++ {
493 var r []byte
494
495 padding := make([]byte, bytesMaxLevels/4) //nolint:gomnd
496 r = append(r, padding...)
497
498 feeIdx := make([]byte, bytesMaxLevels/2) //nolint:gomnd
499 feeIdxBytes := z.FeeIdxs[i].Bytes()
500 copy(feeIdx[len(feeIdx)-len(feeIdxBytes):], feeIdxBytes[:])
501 r = append(r, feeIdx...)
502 b = append(b, r...)
503 }
504
505 // [16 bits] chainID
506 var chainID [2]byte
507 binary.BigEndian.PutUint16(chainID[:], z.Metadata.ChainID)
508 b = append(b, chainID[:]...)
509
510 // [32 bits] currentNumBatch
511 currNumBatchBytes := z.CurrentNumBatch.Bytes()
512 var currNumBatch [4]byte
513 copy(currNumBatch[4-len(currNumBatchBytes):], currNumBatchBytes)
514 b = append(b, currNumBatch[:]...)
515
516 return b, nil
517}