*: support customisable NotaryServiceFeePerKey value

* Add corresponding methods to Notary contract.
* Extend RPC Client API.
* Adjust tests.

internal/fakechain/fakechain.go

@@ -139,6 +139,11 @@ func (chain *FakeChain) GetNotaryBalance(acc util.Uint160) *big.Int {
 	panic("TODO")
 }
 
+// GetNotaryServiceFeePerKey implements Blockchainer interface.
+func (chain *FakeChain) GetNotaryServiceFeePerKey() int64 {
+	panic("TODO")
+}
+
 // GetBaseExecFee implements Policer interface.
 func (chain *FakeChain) GetBaseExecFee() int64 {
 	return interop.DefaultBaseExecFee

pkg/core/blockchain.go

@@ -1499,6 +1499,12 @@ func (bc *Blockchain) GetNotaryBalance(acc util.Uint160) *big.Int {
 	return bc.contracts.Notary.BalanceOf(bc.dao, acc)
 }
 
+// GetNotaryServiceFeePerKey returns NotaryServiceFeePerKey which is a reward per
+// notary request key for designated notary nodes.
+func (bc *Blockchain) GetNotaryServiceFeePerKey() int64 {
+	return bc.contracts.Notary.GetNotaryServiceFeePerKey(bc.dao)
+}
+
 // GetNotaryContractScriptHash returns Notary native contract hash.
 func (bc *Blockchain) GetNotaryContractScriptHash() util.Uint160 {
 	if bc.P2PSigExtensionsEnabled() {
@@ -1913,7 +1919,7 @@ func (bc *Blockchain) verifyAndPoolTx(t *transaction.Transaction, pool *mempool.
 		attrs := t.GetAttributes(transaction.NotaryAssistedT)
 		if len(attrs) != 0 {
 			na := attrs[0].Value.(*transaction.NotaryAssisted)
-			needNetworkFee += (int64(na.NKeys) + 1) * transaction.NotaryServiceFeePerKey
+			needNetworkFee += (int64(na.NKeys) + 1) * bc.contracts.Notary.GetNotaryServiceFeePerKey(bc.dao)
 		}
 	}
 	netFee := t.NetworkFee - needNetworkFee
@@ -2257,7 +2263,7 @@ func (bc *Blockchain) verifyTxWitnesses(t *transaction.Transaction, block *block
 		attrs := t.GetAttributes(transaction.NotaryAssistedT)
 		if len(attrs) != 0 {
 			na := attrs[0].Value.(*transaction.NotaryAssisted)
-			gasLimit -= (int64(na.NKeys) + 1) * transaction.NotaryServiceFeePerKey
+			gasLimit -= (int64(na.NKeys) + 1) * bc.contracts.Notary.GetNotaryServiceFeePerKey(bc.dao)
 		}
 	}
 	for i := range t.Signers {

pkg/core/blockchain_test.go

@@ -316,6 +316,8 @@ func TestVerifyTx(t *testing.T) {
 		require.NoError(t, err)
 	}
 
+	notaryServiceFeePerKey := bc.contracts.Notary.GetNotaryServiceFeePerKey(bc.dao)
+
 	oracleAcc := accs[2]
 	oraclePubs := keys.PublicKeys{oracleAcc.PrivateKey().PublicKey()}
 	require.NoError(t, oracleAcc.ConvertMultisig(1, oraclePubs))
@@ -891,7 +893,7 @@ func TestVerifyTx(t *testing.T) {
 			t.Run("Test verify", func(t *testing.T) {
 				bc.config.P2PSigExtensions = true
 				t.Run("no NotaryAssisted attribute", func(t *testing.T) {
-					tx := getNotaryAssistedTx(1, (1+1)*transaction.NotaryServiceFeePerKey)
+					tx := getNotaryAssistedTx(1, (1+1)*notaryServiceFeePerKey)
 					tx.Attributes = []transaction.Attribute{}
 					tx.Signers = []transaction.Signer{
 						{
@@ -915,7 +917,7 @@ func TestVerifyTx(t *testing.T) {
 					require.Error(t, bc.VerifyTx(tx))
 				})
 				t.Run("no deposit", func(t *testing.T) {
-					tx := getNotaryAssistedTx(1, (1+1)*transaction.NotaryServiceFeePerKey)
+					tx := getNotaryAssistedTx(1, (1+1)*notaryServiceFeePerKey)
 					tx.Signers = []transaction.Signer{
 						{
 							Account: bc.contracts.Notary.Hash,
@@ -938,7 +940,7 @@ func TestVerifyTx(t *testing.T) {
 					require.Error(t, bc.VerifyTx(tx))
 				})
 				t.Run("bad Notary signer scope", func(t *testing.T) {
-					tx := getNotaryAssistedTx(1, (1+1)*transaction.NotaryServiceFeePerKey)
+					tx := getNotaryAssistedTx(1, (1+1)*notaryServiceFeePerKey)
 					tx.Signers = []transaction.Signer{
 						{
 							Account: testchain.CommitteeScriptHash(),
@@ -961,7 +963,7 @@ func TestVerifyTx(t *testing.T) {
 					require.Error(t, bc.VerifyTx(tx))
 				})
 				t.Run("not signed by Notary", func(t *testing.T) {
-					tx := getNotaryAssistedTx(1, (1+1)*transaction.NotaryServiceFeePerKey)
+					tx := getNotaryAssistedTx(1, (1+1)*notaryServiceFeePerKey)
 					tx.Signers = []transaction.Signer{
 						{
 							Account: testchain.CommitteeScriptHash(),
@@ -977,7 +979,7 @@ func TestVerifyTx(t *testing.T) {
 					require.Error(t, bc.VerifyTx(tx))
 				})
 				t.Run("bad Notary node witness", func(t *testing.T) {
-					tx := getNotaryAssistedTx(1, (1+1)*transaction.NotaryServiceFeePerKey)
+					tx := getNotaryAssistedTx(1, (1+1)*notaryServiceFeePerKey)
 					tx.Signers = []transaction.Signer{
 						{
 							Account: testchain.CommitteeScriptHash(),
@@ -1002,7 +1004,7 @@ func TestVerifyTx(t *testing.T) {
 					require.Error(t, bc.VerifyTx(tx))
 				})
 				t.Run("missing payer", func(t *testing.T) {
-					tx := getNotaryAssistedTx(1, (1+1)*transaction.NotaryServiceFeePerKey)
+					tx := getNotaryAssistedTx(1, (1+1)*notaryServiceFeePerKey)
 					tx.Signers = []transaction.Signer{
 						{
 							Account: bc.contracts.Notary.Hash,
@@ -1017,7 +1019,7 @@ func TestVerifyTx(t *testing.T) {
 					require.Error(t, bc.VerifyTx(tx))
 				})
 				t.Run("positive", func(t *testing.T) {
-					tx := getNotaryAssistedTx(1, (1+1)*transaction.NotaryServiceFeePerKey)
+					tx := getNotaryAssistedTx(1, (1+1)*notaryServiceFeePerKey)
 					require.NoError(t, bc.VerifyTx(tx))
 				})
 			})
@@ -1055,7 +1057,7 @@ func TestVerifyTx(t *testing.T) {
 				int64(sizeDelta)*bc.FeePerByte() + // fee for multisig size
 				66*bc.FeePerByte() + // fee for Notary signature size (66 bytes for Invocation script and 0 bytes for Verification script)
 				2*bc.FeePerByte() + // fee for the length of each script in Notary witness (they are nil, so we did not take them into account during `size` calculation)
-				transaction.NotaryServiceFeePerKey + // fee for Notary attribute
+				notaryServiceFeePerKey + // fee for Notary attribute
 				fee.Opcode(bc.GetBaseExecFee(), // Notary verification script
 					opcode.PUSHDATA1, opcode.RET, // invocation script
 					opcode.PUSH0, opcode.SYSCALL, opcode.RET) + // Neo.Native.Call

pkg/core/blockchainer/blockchainer.go

@@ -55,6 +55,7 @@ type Blockchainer interface {
 	GetTokenLastUpdated(acc util.Uint160) (map[int32]uint32, error)
 	GetNotaryContractScriptHash() util.Uint160
 	GetNotaryBalance(acc util.Uint160) *big.Int
+	GetNotaryServiceFeePerKey() int64
 	GetValidators() ([]*keys.PublicKey, error)
 	GetStateModule() StateRoot
 	GetStorageItem(id int32, key []byte) state.StorageItem

pkg/core/native/contract.go

@@ -109,6 +109,7 @@ func NewContracts(cfg config.ProtocolConfiguration) *Contracts {
 		notary.NEO = neo
 		notary.Desig = desig
 		cs.Notary = notary
+		gas.Notary = notary
 		cs.Contracts = append(cs.Contracts, notary)
 	}
 

pkg/core/native/native_gas.go

@@ -19,6 +19,8 @@ import (
 type GAS struct {
 	nep17TokenNative
 	NEO *NEO
+	// Notary is a native Notary contract. It is set only when P2PSigExtensions are on.
+	Notary *Notary
 
 	initialSupply           int64
 	p2pSigExtensionsEnabled bool
@@ -117,7 +119,7 @@ func (g *GAS) OnPersist(ic *interop.Context) error {
 			attrs := tx.GetAttributes(transaction.NotaryAssistedT)
 			if len(attrs) != 0 {
 				na := attrs[0].Value.(*transaction.NotaryAssisted)
-				netFee -= (int64(na.NKeys) + 1) * transaction.NotaryServiceFeePerKey
+				netFee -= (int64(na.NKeys) + 1) * g.Notary.GetNotaryServiceFeePerKey(ic.DAO)
 			}
 		}
 	}

pkg/core/native/native_nep17.go

@@ -342,3 +342,11 @@ func toUint32(s stackitem.Item) uint32 {
 	}
 	return uint32(uint64Value)
 }
+
+func toInt64(s stackitem.Item) int64 {
+	bigInt := toBigInt(s)
+	if !bigInt.IsInt64() {
+		panic("bigint is not an uint64")
+	}
+	return bigInt.Int64()
+}

pkg/core/native/native_test/gas_test.go

@@ -71,6 +71,7 @@ func TestGAS_RewardWithP2PSigExtensionsEnabled(t *testing.T) {
 	e := neotest.NewExecutor(t, bc, validator, committee)
 	gasCommitteeInvoker := e.CommitteeInvoker(e.NativeHash(t, nativenames.Gas))
 	notaryHash := e.NativeHash(t, nativenames.Notary)
+	notaryServiceFeePerKey := e.Chain.GetNotaryServiceFeePerKey()
 
 	// transfer funds to committee
 	e.ValidatorInvoker(e.NativeHash(t, nativenames.Gas)).Invoke(t, true, "transfer", e.Validator.ScriptHash(), e.CommitteeHash, 1000_0000_0000, nil)
@@ -90,7 +91,7 @@ func TestGAS_RewardWithP2PSigExtensionsEnabled(t *testing.T) {
 	}
 
 	// deposit GAS for `signer` with lock until the next block
-	depositAmount := 100_0000 + (2+int64(nKeys))*transaction.NotaryServiceFeePerKey // sysfee + netfee of the next transaction
+	depositAmount := 100_0000 + (2+int64(nKeys))*notaryServiceFeePerKey // sysfee + netfee of the next transaction
 	gasCommitteeInvoker.Invoke(t, true, "transfer", e.CommitteeHash, notaryHash, depositAmount, []interface{}{e.CommitteeHash, e.Chain.BlockHeight() + 1})
 
 	// save initial GAS total supply
@@ -106,7 +107,7 @@ func TestGAS_RewardWithP2PSigExtensionsEnabled(t *testing.T) {
 	tx.Nonce = neotest.Nonce()
 	tx.ValidUntilBlock = e.Chain.BlockHeight() + 1
 	tx.Attributes = append(tx.Attributes, transaction.Attribute{Type: transaction.NotaryAssistedT, Value: &transaction.NotaryAssisted{NKeys: uint8(nKeys)}})
-	tx.NetworkFee = (2 + int64(nKeys)) * transaction.NotaryServiceFeePerKey
+	tx.NetworkFee = (2 + int64(nKeys)) * notaryServiceFeePerKey
 	tx.Signers = []transaction.Signer{
 		{
 			Account: notaryHash,
@@ -131,7 +132,7 @@ func TestGAS_RewardWithP2PSigExtensionsEnabled(t *testing.T) {
 	// check balance of notaries
 	e.CheckGASBalance(t, notaryHash, big.NewInt(int64(depositAmount-tx.SystemFee-tx.NetworkFee)))
 	for _, notaryNode := range notaryNodes {
-		e.CheckGASBalance(t, notaryNode.GetScriptHash(), big.NewInt(int64(transaction.NotaryServiceFeePerKey*(nKeys+1)/nNotaries)))
+		e.CheckGASBalance(t, notaryNode.GetScriptHash(), big.NewInt(notaryServiceFeePerKey*(nKeys+1)/nNotaries))
 	}
 	tsUpdated := getGASTS(t)
 	tsExpected := tsInitial + 5000_0000 - tx.SystemFee

pkg/core/native/native_test/notary_test.go

@@ -32,6 +32,11 @@ func TestNotary_MaxNotValidBeforeDelta(t *testing.T) {
 	testGetSet(t, c, "MaxNotValidBeforeDelta", 140, int64(c.Chain.GetConfig().ValidatorsCount), int64(c.Chain.GetConfig().MaxValidUntilBlockIncrement/2))
 }
 
+func TestNotary_NotaryServiceFeePerKey(t *testing.T) {
+	c := newNotaryClient(t)
+	testGetSet(t, c, "NotaryServiceFeePerKey", 1000_0000, 0, 0)
+}
+
 func TestNotary_Pipeline(t *testing.T) {
 	notaryCommitteeInvoker := newNotaryClient(t)
 	e := notaryCommitteeInvoker.Executor
@@ -39,11 +44,12 @@ func TestNotary_Pipeline(t *testing.T) {
 	gasCommitteeInvoker := e.CommitteeInvoker(e.NativeHash(t, nativenames.Gas))
 
 	notaryHash := notaryCommitteeInvoker.NativeHash(t, nativenames.Notary)
+	feePerKey := e.Chain.GetNotaryServiceFeePerKey()
 	multisigHash := notaryCommitteeInvoker.Validator.ScriptHash() // matches committee's one for single chain
 	depositLock := 100
 
-	checkBalanceOf := func(t *testing.T, acc util.Uint160, expected int) { // we don't have big numbers in this test, thus may use int
+	checkBalanceOf := func(t *testing.T, acc util.Uint160, expected int64) { // we don't have big numbers in this test, thus may use int
-		notaryCommitteeInvoker.CheckGASBalance(t, acc, big.NewInt(int64(expected)))
+		notaryCommitteeInvoker.CheckGASBalance(t, acc, big.NewInt(expected))
 	}
 
 	// check Notary contract has no GAS on the account
@@ -62,47 +68,47 @@ func TestNotary_Pipeline(t *testing.T) {
 	neoCommitteeInvoker.InvokeFail(t, "only GAS can be accepted for deposit", "transfer", multisigHash, notaryHash, int64(1), []interface{}{nil, int64(depositLock)})
 
 	// `onPayment`: insufficient first deposit
-	gasCommitteeInvoker.InvokeFail(t, "first deposit can not be less then", "transfer", multisigHash, notaryHash, int64(2*transaction.NotaryServiceFeePerKey-1), []interface{}{nil, int64(depositLock)})
+	gasCommitteeInvoker.InvokeFail(t, "first deposit can not be less then", "transfer", multisigHash, notaryHash, int64(2*feePerKey-1), []interface{}{nil, int64(depositLock)})
 
 	// `onPayment`: invalid `data` (missing `till` parameter)
-	gasCommitteeInvoker.InvokeFail(t, "`data` parameter should be an array of 2 elements", "transfer", multisigHash, notaryHash, 2*transaction.NotaryServiceFeePerKey, []interface{}{nil})
+	gasCommitteeInvoker.InvokeFail(t, "`data` parameter should be an array of 2 elements", "transfer", multisigHash, notaryHash, 2*feePerKey, []interface{}{nil})
 
 	// `onPayment`: invalid `data` (outdated `till` parameter)
-	gasCommitteeInvoker.InvokeFail(t, "`till` shouldn't be less then the chain's height", "transfer", multisigHash, notaryHash, 2*transaction.NotaryServiceFeePerKey, []interface{}{nil, int64(0)})
+	gasCommitteeInvoker.InvokeFail(t, "`till` shouldn't be less then the chain's height", "transfer", multisigHash, notaryHash, 2*feePerKey, []interface{}{nil, int64(0)})
 
 	// `onPayment`: good
-	gasCommitteeInvoker.Invoke(t, true, "transfer", multisigHash, notaryHash, 2*transaction.NotaryServiceFeePerKey, []interface{}{nil, int64(depositLock)})
+	gasCommitteeInvoker.Invoke(t, true, "transfer", multisigHash, notaryHash, 2*feePerKey, []interface{}{nil, int64(depositLock)})
-	checkBalanceOf(t, notaryHash, 2*transaction.NotaryServiceFeePerKey)
+	checkBalanceOf(t, notaryHash, 2*feePerKey)
 
 	// `expirationOf`: check `till` was set
 	notaryCommitteeInvoker.Invoke(t, depositLock, "expirationOf", multisigHash)
 
 	// `balanceOf`: check deposited amount for the multisig account
-	notaryCommitteeInvoker.Invoke(t, 2*transaction.NotaryServiceFeePerKey, "balanceOf", multisigHash)
+	notaryCommitteeInvoker.Invoke(t, 2*feePerKey, "balanceOf", multisigHash)
 
 	// `onPayment`: good second deposit and explicit `to` paramenter
-	gasCommitteeInvoker.Invoke(t, true, "transfer", multisigHash, notaryHash, transaction.NotaryServiceFeePerKey, []interface{}{multisigHash, int64(depositLock + 1)})
+	gasCommitteeInvoker.Invoke(t, true, "transfer", multisigHash, notaryHash, feePerKey, []interface{}{multisigHash, int64(depositLock + 1)})
-	checkBalanceOf(t, notaryHash, 3*transaction.NotaryServiceFeePerKey)
+	checkBalanceOf(t, notaryHash, 3*feePerKey)
 
 	// `balanceOf`: check deposited amount for the multisig account
-	notaryCommitteeInvoker.Invoke(t, 3*transaction.NotaryServiceFeePerKey, "balanceOf", multisigHash)
+	notaryCommitteeInvoker.Invoke(t, 3*feePerKey, "balanceOf", multisigHash)
 
 	// `expirationOf`: check `till` is updated.
 	notaryCommitteeInvoker.Invoke(t, depositLock+1, "expirationOf", multisigHash)
 
 	// `onPayment`: empty payment, should fail because `till` less then the previous one
 	gasCommitteeInvoker.InvokeFail(t, "`till` shouldn't be less then the previous value", "transfer", multisigHash, notaryHash, int64(0), []interface{}{multisigHash, int64(depositLock)})
-	checkBalanceOf(t, notaryHash, 3*transaction.NotaryServiceFeePerKey)
+	checkBalanceOf(t, notaryHash, 3*feePerKey)
 	notaryCommitteeInvoker.Invoke(t, depositLock+1, "expirationOf", multisigHash)
 
 	// `onPayment`: empty payment, should fail because `till` less then the chain height
 	gasCommitteeInvoker.InvokeFail(t, "`till` shouldn't be less then the chain's height", "transfer", multisigHash, notaryHash, int64(0), []interface{}{multisigHash, int64(1)})
-	checkBalanceOf(t, notaryHash, 3*transaction.NotaryServiceFeePerKey)
+	checkBalanceOf(t, notaryHash, 3*feePerKey)
 	notaryCommitteeInvoker.Invoke(t, depositLock+1, "expirationOf", multisigHash)
 
 	// `onPayment`: empty payment, should successfully update `till`
 	gasCommitteeInvoker.Invoke(t, true, "transfer", multisigHash, notaryHash, int64(0), []interface{}{multisigHash, int64(depositLock + 2)})
-	checkBalanceOf(t, notaryHash, 3*transaction.NotaryServiceFeePerKey)
+	checkBalanceOf(t, notaryHash, 3*feePerKey)
 	notaryCommitteeInvoker.Invoke(t, depositLock+2, "expirationOf", multisigHash)
 
 	// `lockDepositUntil`: bad witness
@@ -127,11 +133,11 @@ func TestNotary_Pipeline(t *testing.T) {
 
 	// `withdraw`: bad witness
 	notaryAccInvoker.Invoke(t, false, "withdraw", multisigHash, accHash)
-	notaryCommitteeInvoker.Invoke(t, 3*transaction.NotaryServiceFeePerKey, "balanceOf", multisigHash)
+	notaryCommitteeInvoker.Invoke(t, 3*feePerKey, "balanceOf", multisigHash)
 
 	// `withdraw`: locked deposit
 	notaryCommitteeInvoker.Invoke(t, false, "withdraw", multisigHash, multisigHash)
-	notaryCommitteeInvoker.Invoke(t, 3*transaction.NotaryServiceFeePerKey, "balanceOf", multisigHash)
+	notaryCommitteeInvoker.Invoke(t, 3*feePerKey, "balanceOf", multisigHash)
 
 	// `withdraw`: unlock deposit and transfer GAS back to owner
 	e.GenerateNewBlocks(t, depositLock)
@@ -143,13 +149,13 @@ func TestNotary_Pipeline(t *testing.T) {
 	notaryCommitteeInvoker.Invoke(t, false, "withdraw", multisigHash, accHash)
 
 	// `onPayment`: good first deposit to other account, should set default `till` even if other `till` value is provided
-	gasCommitteeInvoker.Invoke(t, true, "transfer", multisigHash, notaryHash, 2*transaction.NotaryServiceFeePerKey, []interface{}{accHash, int64(math.MaxUint32 - 1)})
+	gasCommitteeInvoker.Invoke(t, true, "transfer", multisigHash, notaryHash, 2*feePerKey, []interface{}{accHash, int64(math.MaxUint32 - 1)})
-	checkBalanceOf(t, notaryHash, 2*transaction.NotaryServiceFeePerKey)
+	checkBalanceOf(t, notaryHash, 2*feePerKey)
 	notaryCommitteeInvoker.Invoke(t, 5760+e.Chain.BlockHeight()-1, "expirationOf", accHash)
 
 	// `onPayment`: good second deposit to other account, shouldn't update `till` even if other `till` value is provided
-	gasCommitteeInvoker.Invoke(t, true, "transfer", multisigHash, notaryHash, transaction.NotaryServiceFeePerKey, []interface{}{accHash, int64(math.MaxUint32 - 1)})
+	gasCommitteeInvoker.Invoke(t, true, "transfer", multisigHash, notaryHash, feePerKey, []interface{}{accHash, int64(math.MaxUint32 - 1)})
-	checkBalanceOf(t, notaryHash, 3*transaction.NotaryServiceFeePerKey)
+	checkBalanceOf(t, notaryHash, 3*feePerKey)
 	notaryCommitteeInvoker.Invoke(t, 5760+e.Chain.BlockHeight()-3, "expirationOf", accHash)
 }
 
@@ -161,6 +167,7 @@ func TestNotary_NotaryNodesReward(t *testing.T) {
 		designationCommitteeInvoker := e.CommitteeInvoker(e.NativeHash(t, nativenames.Designation))
 
 		notaryHash := notaryCommitteeInvoker.NativeHash(t, nativenames.Notary)
+		feePerKey := e.Chain.GetNotaryServiceFeePerKey()
 		multisigHash := notaryCommitteeInvoker.Validator.ScriptHash() // matches committee's one for single chain
 
 		var err error
@@ -180,7 +187,7 @@ func TestNotary_NotaryNodesReward(t *testing.T) {
 		}
 
 		// deposit GAS for `signer` with lock until the next block
-		depositAmount := 100_0000 + (2+int64(nKeys))*transaction.NotaryServiceFeePerKey // sysfee + netfee of the next transaction
+		depositAmount := 100_0000 + (2+int64(nKeys))*feePerKey // sysfee + netfee of the next transaction
 		if !spendFullDeposit {
 			depositAmount += 1_0000
 		}
@@ -191,7 +198,7 @@ func TestNotary_NotaryNodesReward(t *testing.T) {
 		tx.Nonce = neotest.Nonce()
 		tx.ValidUntilBlock = e.Chain.BlockHeight() + 1
 		tx.Attributes = append(tx.Attributes, transaction.Attribute{Type: transaction.NotaryAssistedT, Value: &transaction.NotaryAssisted{NKeys: uint8(nKeys)}})
-		tx.NetworkFee = (2 + int64(nKeys)) * transaction.NotaryServiceFeePerKey
+		tx.NetworkFee = (2 + int64(nKeys)) * feePerKey
 		tx.Signers = []transaction.Signer{
 			{
 				Account: notaryHash,
@@ -215,7 +222,7 @@ func TestNotary_NotaryNodesReward(t *testing.T) {
 
 		e.CheckGASBalance(t, notaryHash, big.NewInt(int64(depositAmount-tx.SystemFee-tx.NetworkFee)))
 		for _, notaryNode := range notaryNodes {
-			e.CheckGASBalance(t, notaryNode.GetScriptHash(), big.NewInt(int64(transaction.NotaryServiceFeePerKey*(nKeys+1)/nNotaryNodes)))
+			e.CheckGASBalance(t, notaryNode.GetScriptHash(), big.NewInt(feePerKey*int64((nKeys+1))/int64(nNotaryNodes)))
 		}
 	}
 

pkg/core/native/notary.go

@@ -39,6 +39,7 @@ type Notary struct {
 	// blockchain DAO persisting. If true, we can safely use cached values.
 	isValid                bool
 	maxNotValidBeforeDelta uint32
+	notaryServiceFeePerKey int64
 }
 
 const (
@@ -47,9 +48,13 @@ const (
 	prefixDeposit                 = 1
 	defaultDepositDeltaTill       = 5760
 	defaultMaxNotValidBeforeDelta = 140       // 20 rounds for 7 validators, a little more than half an hour
+	defaultNotaryServiceFeePerKey = 1000_0000 // 0.1 GAS
 )
 
-var maxNotValidBeforeDeltaKey = []byte{10}
+var (
+	maxNotValidBeforeDeltaKey = []byte{10}
+	notaryServiceFeeKey       = []byte{5}
+)
 
 // newNotary returns Notary native contract.
 func newNotary() *Notary {
@@ -99,6 +104,15 @@ func newNotary() *Notary {
 	md = newMethodAndPrice(n.setMaxNotValidBeforeDelta, 1<<15, callflag.States)
 	n.AddMethod(md, desc)
 
+	desc = newDescriptor("getNotaryServiceFeePerKey", smartcontract.IntegerType)
+	md = newMethodAndPrice(n.getNotaryServiceFeePerKey, 1<<15, callflag.ReadStates)
+	n.AddMethod(md, desc)
+
+	desc = newDescriptor("setNotaryServiceFeePerKey", smartcontract.VoidType,
+		manifest.NewParameter("value", smartcontract.IntegerType))
+	md = newMethodAndPrice(n.setNotaryServiceFeePerKey, 1<<15, callflag.States)
+	n.AddMethod(md, desc)
+
 	return n
 }
 
@@ -110,8 +124,10 @@ func (n *Notary) Metadata() *interop.ContractMD {
 // Initialize initializes Notary native contract and implements Contract interface.
 func (n *Notary) Initialize(ic *interop.Context) error {
 	setIntWithKey(n.ID, ic.DAO, maxNotValidBeforeDeltaKey, defaultMaxNotValidBeforeDelta)
+	setIntWithKey(n.ID, ic.DAO, notaryServiceFeeKey, defaultNotaryServiceFeePerKey)
 	n.isValid = true
 	n.maxNotValidBeforeDelta = defaultMaxNotValidBeforeDelta
+	n.notaryServiceFeePerKey = defaultNotaryServiceFeePerKey
 	return nil
 }
 
@@ -150,7 +166,8 @@ func (n *Notary) OnPersist(ic *interop.Context) error {
 	if nFees == 0 {
 		return nil
 	}
-	singleReward := calculateNotaryReward(nFees, len(notaries))
+	feePerKey := n.GetNotaryServiceFeePerKey(ic.DAO)
+	singleReward := calculateNotaryReward(nFees, feePerKey, len(notaries))
 	for _, notary := range notaries {
 		n.GAS.mint(ic, notary.GetScriptHash(), singleReward, false)
 	}
@@ -166,6 +183,7 @@ func (n *Notary) PostPersist(ic *interop.Context) error {
 	}
 
 	n.maxNotValidBeforeDelta = uint32(getIntWithKey(n.ID, ic.DAO, maxNotValidBeforeDeltaKey))
+	n.notaryServiceFeePerKey = getIntWithKey(n.ID, ic.DAO, notaryServiceFeeKey)
 	n.isValid = true
 	return nil
 }
@@ -198,9 +216,10 @@ func (n *Notary) onPayment(ic *interop.Context, args []stackitem.Item) stackitem
 	if deposit != nil && till < deposit.Till {
 		panic(fmt.Errorf("`till` shouldn't be less then the previous value %d", deposit.Till))
 	}
+	feePerKey := n.GetNotaryServiceFeePerKey(ic.DAO)
 	if deposit == nil {
-		if amount.Cmp(big.NewInt(2*transaction.NotaryServiceFeePerKey)) < 0 {
+		if amount.Cmp(big.NewInt(2*feePerKey)) < 0 {
-			panic(fmt.Errorf("first deposit can not be less then %d, got %d", 2*transaction.NotaryServiceFeePerKey, amount.Int64()))
+			panic(fmt.Errorf("first deposit can not be less then %d, got %d", 2*feePerKey, amount.Int64()))
 		}
 		deposit = &state.Deposit{
 			Amount: new(big.Int),
@@ -398,6 +417,37 @@ func (n *Notary) setMaxNotValidBeforeDelta(ic *interop.Context, args []stackitem
 	return stackitem.Null{}
 }
 
+// getNotaryServiceFeePerKey is Notary contract method and returns a reward per notary request key for notary nodes.
+func (n *Notary) getNotaryServiceFeePerKey(ic *interop.Context, _ []stackitem.Item) stackitem.Item {
+	return stackitem.NewBigInteger(big.NewInt(int64(n.GetNotaryServiceFeePerKey(ic.DAO))))
+}
+
+// GetNotaryServiceFeePerKey is an internal representation of Notary getNotaryServiceFeePerKey method.
+func (n *Notary) GetNotaryServiceFeePerKey(dao *dao.Simple) int64 {
+	n.lock.RLock()
+	defer n.lock.RUnlock()
+	if n.isValid {
+		return n.notaryServiceFeePerKey
+	}
+	return getIntWithKey(n.ID, dao, notaryServiceFeeKey)
+}
+
+// setNotaryServiceFeePerKey is Notary contract method and sets a reward per notary request key for notary nodes.
+func (n *Notary) setNotaryServiceFeePerKey(ic *interop.Context, args []stackitem.Item) stackitem.Item {
+	value := toInt64(args[0])
+	if value < 0 {
+		panic("NotaryServiceFeePerKey can't be negative")
+	}
+	if !n.NEO.checkCommittee(ic) {
+		panic("invalid committee signature")
+	}
+	n.lock.Lock()
+	defer n.lock.Unlock()
+	setIntWithKey(n.ID, ic.DAO, notaryServiceFeeKey, int64(value))
+	n.isValid = false
+	return stackitem.Null{}
+}
+
 // GetDepositFor returns state.Deposit for the account specified. It returns nil in case if
 // deposit is not found in storage and panics in case of any other error.
 func (n *Notary) GetDepositFor(dao *dao.Simple, acc util.Uint160) *state.Deposit {
@@ -426,6 +476,6 @@ func (n *Notary) removeDepositFor(dao *dao.Simple, acc util.Uint160) {
 }
 
 // calculateNotaryReward calculates the reward for a single notary node based on FEE's count and Notary nodes count.
-func calculateNotaryReward(nFees int64, notariesCount int) *big.Int {
+func calculateNotaryReward(nFees int64, feePerKey int64, notariesCount int) *big.Int {
-	return big.NewInt(nFees * transaction.NotaryServiceFeePerKey / int64(notariesCount))
+	return big.NewInt(nFees * feePerKey / int64(notariesCount))
 }

pkg/core/transaction/notary_assisted.go

@@ -6,9 +6,6 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/io"
 )
 
-// NotaryServiceFeePerKey is a reward per key for notary nodes.
-const NotaryServiceFeePerKey = 1000_0000 // 0.1 GAS
-
 // NotaryAssisted represents attribute for notary service transactions.
 type NotaryAssisted struct {
 	NKeys uint8 `json:"nkeys"`

pkg/rpc/client/native.go

@@ -141,3 +141,13 @@ func (c *Client) NNSGetAllRecords(nnsHash util.Uint160, name string) ([]nns.Reco
 	}
 	return rss, nil
 }
+
+// GetNotaryServiceFeePerKey returns a reward per notary request key for designated
+// notary nodes. It doesn't cache the result.
+func (c *Client) GetNotaryServiceFeePerKey() (int64, error) {
+	notaryHash, err := c.GetNativeContractHash(nativenames.Notary)
+	if err != nil {
+		return 0, fmt.Errorf("failed to get native Notary hash: %w", err)
+	}
+	return c.invokeNativeGetMethod(notaryHash, "getNotaryServiceFeePerKey")
+}

pkg/rpc/client/rpc.go

@@ -878,7 +878,11 @@ func (c *Client) CalculateNotaryFee(nKeys uint8) (int64, error) {
 	if err != nil {
 		return 0, fmt.Errorf("failed to get FeePerByte: %w", err)
 	}
-	return int64((nKeys+1))*transaction.NotaryServiceFeePerKey + // fee for NotaryAssisted attribute
+	feePerKey, err := c.GetNotaryServiceFeePerKey()
+	if err != nil {
+		return 0, fmt.Errorf("failed to get NotaryServiceFeePerKey: %w", err)
+	}
+	return int64((nKeys+1))*feePerKey + // fee for NotaryAssisted attribute
 			fee.Opcode(baseExecFee, // Notary node witness
 				opcode.PUSHDATA1, opcode.RET, // invocation script
 				opcode.PUSH0, opcode.SYSCALL, opcode.RET) + // System.Contract.CallNative

pkg/rpc/server/client_test.go

@@ -983,3 +983,18 @@ func TestClient_NNS(t *testing.T) {
 		require.Error(t, err)
 	})
 }
+
+func TestClient_GetNotaryServiceFeePerKey(t *testing.T) {
+	chain, rpcSrv, httpSrv := initServerWithInMemoryChain(t)
+	defer chain.Close()
+	defer func() { _ = rpcSrv.Shutdown() }()
+
+	c, err := client.New(context.Background(), httpSrv.URL, client.Options{})
+	require.NoError(t, err)
+	require.NoError(t, c.Init())
+
+	var defaultNotaryServiceFeePerKey int64 = 1000_0000
+	actual, err := c.GetNotaryServiceFeePerKey()
+	require.NoError(t, err)
+	require.Equal(t, defaultNotaryServiceFeePerKey, actual)
+}