diff --git a/.golangci.yml b/.golangci.yml
index 7a94ed81d..a7b264e22 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -1,4 +1,7 @@
 version: "2"
+run:
+  build-tags:
+    - endtoendtests
 linters:
   enable:
     - exhaustive
diff --git a/Makefile b/Makefile
index 936749638..36560b222 100644
--- a/Makefile
+++ b/Makefile
@@ -516,6 +516,17 @@ start-postgres: ## Run the PostgreSQL 16 docker container
 	@docker run --rm --name postgres -p 5432:5432 -d -e POSTGRES_PASSWORD=password -e POSTGRES_DB=rollupsdb -v $(CURDIR)/test/postgres/init-test-db.sh:/docker-entrypoint-initdb.d/init-test-db.sh postgres:18-alpine
 	@$(MAKE) migrate
 
+start-awslocalstack: ## Run the AWS LocalStack docker container
+	@echo "Starting AWS localstack"
+	@docker run --rm --name awslocalstack -p 127.0.0.1:4566:4566 -d -e SERVICES=kms localstack/localstack:4.14.0
+	@echo "Add the following variables to run integration test with AWS services:"
+	@echo "  export AWS_ACCESS_KEY_ID=test"
+	@echo "  export AWS_SECRET_ACCESS_KEY=test"
+	@echo "  export AWS_REGION=us-east-1"
+	@echo "  export AWS_ENDPOINT_URL_KMS=http://localhost:4566"
+	@echo "  export LOCALSTACK_KMS_ENDPOINT=http://localhost:4566"
+	@echo "  export LOCALSTACK_KMS_REQUIRED=true"
+
 start: start-postgres start-devnet ## Start the anvil devnet and PostgreSQL 16 docker containers
 
 stop-devnet: ## Stop the anvil devnet docker container
@@ -524,6 +535,9 @@ stop-devnet: ## Stop the anvil devnet docker container
 stop-postgres: ## Stop the PostgreSQL 16 docker container
 	@docker stop postgres || true
 
+stop-awslocalstack: ## Stop the AWS LocalStack docker container
+	@docker stop awslocalstack || true
+
 stop: stop-devnet stop-postgres ## Stop all running docker containers
 
 restart-devnet: ## Restart the anvil devnet docker container
diff --git a/cmd/cartesi-rollups-cli/root/deposit/deposit.go b/cmd/cartesi-rollups-cli/root/deposit/deposit.go
index 536717419..5b08cf460 100644
--- a/cmd/cartesi-rollups-cli/root/deposit/deposit.go
+++ b/cmd/cartesi-rollups-cli/root/deposit/deposit.go
@@ -13,6 +13,7 @@ import (
 	"github.com/cartesi/rollups-node/cmd/cartesi-rollups-cli/util"
 	"github.com/cartesi/rollups-node/internal/cli"
 	"github.com/cartesi/rollups-node/internal/config"
+	"github.com/cartesi/rollups-node/internal/config/auth"
 	"github.com/cartesi/rollups-node/pkg/contracts/iapplication"
 	"github.com/cartesi/rollups-node/pkg/contracts/ierc20errors"
 	"github.com/cartesi/rollups-node/pkg/contracts/ierc20metadata"
@@ -113,7 +114,7 @@ func runERC20(cmd *cobra.Command, args []string) {
 	cobra.CheckErr(err)
 	chainID, err := client.ChainID(ctx)
 	cobra.CheckErr(err)
-	txOpts, err := cli.GetTransactOpts(ctx, chainID)
+	txOptsFactory, err := auth.GetTransactOptsFactory(ctx, chainID)
 	cobra.CheckErr(err)
 
 	if !skipConfirmation {
@@ -124,7 +125,7 @@ func runERC20(cmd *cobra.Command, args []string) {
 			"  token:       %s\n"+
 			"  amount:      %s\n"+
 			"  approve:     %t\n",
-			txOpts.From, appAddr, portalAddr, tokenAddr, amount.String(), approveParam)
+			txOptsFactory.From(), appAddr, portalAddr, tokenAddr, amount.String(), approveParam)
 		confirmed, promptErr := cli.ConfirmPrompt("Do you want to continue?")
 		cobra.CheckErr(promptErr)
 		if !confirmed {
@@ -137,7 +138,7 @@ func runERC20(cmd *cobra.Command, args []string) {
 	if approveParam {
 		token, err := ierc20metadata.NewIERC20Metadata(tokenAddr, client)
 		cobra.CheckErr(err)
-		approveOpts, err := cli.GetTransactOpts(ctx, chainID)
+		approveOpts, err := cli.GetTransactOptsFromFactory(ctx, txOptsFactory)
 		cobra.CheckErr(err)
 		tx, err := token.Approve(approveOpts, portalAddr, amount)
 		cobra.CheckErr(cli.DecorateRevert(err,
@@ -153,7 +154,7 @@ func runERC20(cmd *cobra.Command, args []string) {
 
 	portal, err := ierc20portal.NewIERC20Portal(portalAddr, client)
 	cobra.CheckErr(err)
-	depositOpts, err := cli.GetTransactOpts(ctx, chainID)
+	depositOpts, err := cli.GetTransactOptsFromFactory(ctx, txOptsFactory)
 	cobra.CheckErr(err)
 	tx, err := portal.DepositERC20Tokens(depositOpts, tokenAddr, appAddr, amount, execData)
 	// The revert can come from three layers: the portal itself
diff --git a/internal/claimer/service.go b/internal/claimer/service.go
index 1a1399ed3..9e4fc4df9 100644
--- a/internal/claimer/service.go
+++ b/internal/claimer/service.go
@@ -77,8 +77,7 @@ type PersistentConfig struct {
 	ChainID                uint64
 }
 
-func Create(ctx context.Context, c *CreateInfo) (*Service, error) {
-	var err error
+func Create(ctx context.Context, c *CreateInfo) (_ *Service, err error) {
 
 	if c == nil {
 		return nil, errors.New("invalid CreateInfo is nil")
@@ -101,6 +100,11 @@ func Create(ctx context.Context, c *CreateInfo) (*Service, error) {
 	if err != nil {
 		return nil, fmt.Errorf("creating base service: %w", err)
 	}
+	defer func() {
+		if err != nil && s.Ticker != nil {
+			s.Ticker.Stop()
+		}
+	}()
 
 	nodeConfig, err := setupPersistentConfig(ctx, s.Logger, c.Repository, &c.Config)
 	if err != nil {
@@ -138,6 +142,7 @@ func Create(ctx context.Context, c *CreateInfo) (*Service, error) {
 		if err != nil {
 			return nil, fmt.Errorf("getting transaction options: %w", err)
 		}
+		s.Logger.Info("Claim submitter identity", "address", txOptsFactory.From())
 	}
 
 	s.repository = c.Repository
diff --git a/internal/cli/ethereum.go b/internal/cli/ethereum.go
index e44018c09..00357d81d 100644
--- a/internal/cli/ethereum.go
+++ b/internal/cli/ethereum.go
@@ -10,6 +10,7 @@ import (
 
 	"github.com/cartesi/rollups-node/internal/config"
 	"github.com/cartesi/rollups-node/internal/config/auth"
+	"github.com/cartesi/rollups-node/pkg/ethutil"
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 )
 
@@ -18,7 +19,13 @@ func GetTransactOpts(ctx context.Context, chainId *big.Int) (*bind.TransactOpts,
 	if err != nil {
 		return nil, err
 	}
+	return GetTransactOptsFromFactory(ctx, factory)
+}
 
+func GetTransactOptsFromFactory(
+	ctx context.Context,
+	factory ethutil.TransactOptsFactory,
+) (*bind.TransactOpts, error) {
 	txOpts, err := factory.NewTransactOpts(ctx)
 	if err != nil {
 		return nil, err
diff --git a/internal/config/auth/auth.go b/internal/config/auth/auth.go
index 408f7b13a..5bfa995df 100644
--- a/internal/config/auth/auth.go
+++ b/internal/config/auth/auth.go
@@ -5,6 +5,7 @@ package auth
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"math/big"
 
@@ -21,7 +22,17 @@ import (
 	"github.com/cartesi/rollups-node/pkg/ethutil"
 )
 
+// ErrSignerUnavailable identifies transient failures while acquiring the AWS
+// KMS-backed signer. Callers may use this to degrade and retry signing services
+// without treating unrelated configuration or service creation errors as
+// recoverable.
+var ErrSignerUnavailable = errors.New("signer unavailable")
+
 func GetTransactOptsFactory(ctx context.Context, chainId *big.Int) (ethutil.TransactOptsFactory, error) {
+	if chainId == nil || chainId.Sign() <= 0 {
+		return nil, bind.ErrNoChainID
+	}
+
 	authKind, err := GetAuthKind()
 	if err != nil {
 		return nil, err
@@ -60,21 +71,25 @@ func GetTransactOptsFactory(ctx context.Context, chainId *big.Int) (ethutil.Tran
 		}
 		return ethutil.NewStaticTransactOptsFactory(txOpts), nil
 	case AuthKindAWS:
-		awsc, err := aws_cfg.LoadDefaultConfig(ctx)
+		keyId, err := GetAuthAwsKmsKeyId()
 		if err != nil {
 			return nil, err
 		}
-		kmsConfig := aws_kms.NewFromConfig(awsc)
-		authAwsKmsKeyId, err := GetAuthAwsKmsKeyId()
+		awsCfg, err := aws_cfg.LoadDefaultConfig(ctx)
 		if err != nil {
 			return nil, err
 		}
-		return signtx.CreateAWSTransactOptsFactory(
+		kmsClient := aws_kms.NewFromConfig(awsCfg)
+		factory, err := signtx.CreateAWSTransactOptsFactory(
 			ctx,
-			kmsConfig,
-			aws.String(authAwsKmsKeyId.Value),
-			types.NewEIP155Signer(chainId),
+			kmsClient,
+			aws.String(keyId.Value),
+			types.LatestSignerForChainID(chainId),
 		)
+		if err != nil {
+			return nil, fmt.Errorf("%w: %w", ErrSignerUnavailable, err)
+		}
+		return factory, nil
 	default:
 		return nil, fmt.Errorf("no valid authentication method found")
 	}
diff --git a/internal/config/auth/auth_test.go b/internal/config/auth/auth_test.go
new file mode 100644
index 000000000..ad5a57d6d
--- /dev/null
+++ b/internal/config/auth/auth_test.go
@@ -0,0 +1,175 @@
+// (c) Cartesi and individual authors (see AUTHORS)
+// SPDX-License-Identifier: Apache-2.0 (see LICENSE)
+
+package auth
+
+import (
+	"crypto/ecdsa"
+	"crypto/rand"
+	"encoding/asn1"
+	"encoding/base64"
+	"encoding/json"
+	"math/big"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/spf13/viper"
+	"github.com/stretchr/testify/require"
+
+	. "github.com/cartesi/rollups-node/internal/config"
+)
+
+func TestGetTransactOptsFactoryAWSSignsDynamicFeeTransaction(t *testing.T) {
+	server := newFakeKMSServer(t)
+	t.Cleanup(server.Close)
+	setupAWSAuth(t, server.URL)
+
+	chainID := big.NewInt(31337)
+	factory, err := GetTransactOptsFactory(t.Context(), chainID)
+	require.NoError(t, err)
+	opts, err := factory.NewTransactOpts(t.Context())
+	require.NoError(t, err)
+
+	to := common.Address{0x01}
+	tests := []struct {
+		name string
+		tx   *types.Transaction
+	}{
+		{
+			name: "dynamic fee",
+			tx: types.NewTx(&types.DynamicFeeTx{
+				ChainID:   chainID,
+				Nonce:     1,
+				GasTipCap: big.NewInt(1),
+				GasFeeCap: big.NewInt(2),
+				Gas:       21000,
+				To:        &to,
+				Value:     big.NewInt(3),
+			}),
+		},
+		{
+			name: "legacy",
+			tx: types.NewTx(&types.LegacyTx{
+				Nonce:    2,
+				GasPrice: big.NewInt(1),
+				Gas:      21000,
+				To:       &to,
+				Value:    big.NewInt(3),
+			}),
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			signed, err := opts.Signer(opts.From, test.tx)
+			require.NoError(t, err)
+			sender, err := types.Sender(types.LatestSignerForChainID(chainID), signed)
+			require.NoError(t, err)
+			require.Equal(t, opts.From, sender)
+		})
+	}
+}
+
+func TestGetTransactOptsFactoryRejectsInvalidChainID(t *testing.T) {
+	tests := []struct {
+		name    string
+		chainID *big.Int
+	}{
+		{name: "nil", chainID: nil},
+		{name: "zero", chainID: big.NewInt(0)},
+		{name: "negative", chainID: big.NewInt(-1)},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			factory, err := GetTransactOptsFactory(t.Context(), test.chainID)
+			require.Nil(t, factory)
+			require.ErrorIs(t, err, bind.ErrNoChainID)
+		})
+	}
+}
+
+func setupAWSAuth(t *testing.T, endpoint string) {
+	t.Helper()
+	viper.Reset()
+	t.Cleanup(viper.Reset)
+	viper.Set(AUTH_KIND, "aws")
+	viper.Set(AUTH_AWS_KMS_KEY_ID, "alias/test-key")
+
+	// Static dummy credentials keep the AWS SDK hermetic: it never consults
+	// shared config files, credential services, or EC2 instance metadata.
+	t.Setenv("AWS_ACCESS_KEY_ID", "test")
+	t.Setenv("AWS_SECRET_ACCESS_KEY", "test")
+	t.Setenv("AWS_REGION", "us-east-1")
+	t.Setenv("AWS_ENDPOINT_URL_KMS", endpoint)
+	t.Setenv("AWS_EC2_METADATA_DISABLED", "true")
+}
+
+func newFakeKMSServer(t *testing.T) *httptest.Server {
+	t.Helper()
+
+	privateKey, err := crypto.GenerateKey()
+	require.NoError(t, err)
+
+	publicKey, err := asn1.Marshal(struct {
+		Algorithm struct {
+			Algorithm  asn1.ObjectIdentifier
+			Parameters asn1.ObjectIdentifier
+		}
+		SubjectPublicKey asn1.BitString
+	}{
+		Algorithm: struct {
+			Algorithm  asn1.ObjectIdentifier
+			Parameters asn1.ObjectIdentifier
+		}{
+			Algorithm:  asn1.ObjectIdentifier{1, 2, 840, 10045, 2, 1},
+			Parameters: asn1.ObjectIdentifier{1, 3, 132, 0, 10},
+		},
+		SubjectPublicKey: asn1.BitString{Bytes: crypto.FromECDSAPub(&privateKey.PublicKey)},
+	})
+	require.NoError(t, err)
+
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/x-amz-json-1.1")
+		switch r.Header.Get("X-Amz-Target") {
+		case "TrentService.GetPublicKey":
+			writeKMSJSON(t, w, map[string]any{
+				"KeyId":     "alias/test-key",
+				"KeySpec":   "ECC_SECG_P256K1",
+				"KeyUsage":  "SIGN_VERIFY",
+				"PublicKey": base64.StdEncoding.EncodeToString(publicKey),
+			})
+		case "TrentService.Sign":
+			var input struct {
+				Message string `json:"Message"`
+			}
+			require.NoError(t, json.NewDecoder(r.Body).Decode(&input))
+			digest, err := base64.StdEncoding.DecodeString(input.Message)
+			require.NoError(t, err)
+			r, s, err := ecdsa.Sign(rand.Reader, privateKey, digest)
+			require.NoError(t, err)
+			signature, err := asn1.Marshal(struct {
+				R *big.Int
+				S *big.Int
+			}{R: r, S: s})
+			require.NoError(t, err)
+			writeKMSJSON(t, w, map[string]any{
+				"KeyId":            "alias/test-key",
+				"Signature":        base64.StdEncoding.EncodeToString(signature),
+				"SigningAlgorithm": "ECDSA_SHA_256",
+			})
+		default:
+			http.Error(w, "unexpected KMS operation", http.StatusBadRequest)
+		}
+	}))
+}
+
+func writeKMSJSON(t *testing.T, w http.ResponseWriter, value any) {
+	t.Helper()
+	require.NoError(t, json.NewEncoder(w).Encode(value))
+}
diff --git a/internal/config/generate/Config.toml b/internal/config/generate/Config.toml
index c5d298a78..c77bdd183 100644
--- a/internal/config/generate/Config.toml
+++ b/internal/config/generate/Config.toml
@@ -360,18 +360,17 @@ used-by = ["claimer", "node", "cli", "prt"]
 [auth.CARTESI_AUTH_AWS_KMS_KEY_ID]
 go-type = "RedactedString"
 description = """
-If set, the node will use the AWS KMS service with this key ID to sign transactions.
+An AWS KMS key ID, alias, or ARN.
 
-Must be set alongside `CARTESI_AUTH_AWS_KMS_REGION`."""
-omit = true
-used-by = ["claimer", "node", "cli", "prt"]
+If set, the node will use the AWS KMS service with this key to sign transactions.
 
-[auth.CARTESI_AUTH_AWS_KMS_REGION]
-go-type = "RedactedString"
-description = """
-An AWS KMS Region.
+Everything else about the AWS connection — region, endpoint, and credentials — is
+resolved by the AWS SDK's standard chain, not by CARTESI_ variables. See the
+"Externally-provided configuration" section for the variables involved.
 
-Must be set alongside `CARTESI_AUTH_AWS_KMS_KEY_ID`."""
+Prefer an ARN or a bare key ID over an alias: an alias is resolved per-region, so
+the same alias in a different region names a different key and therefore a
+different signing address."""
 omit = true
 used-by = ["claimer", "node", "cli", "prt"]
 
diff --git a/internal/config/generate/docs.go b/internal/config/generate/docs.go
index 78b44d795..8820686b2 100644
--- a/internal/config/generate/docs.go
+++ b/internal/config/generate/docs.go
@@ -44,7 +44,8 @@ DO NOT EDIT.
 # Node Configuration
 
 The node is configurable through environment variables.
-(There is no other way to configure it.)
+Variables prefixed CARTESI_ are listed below. A few subsystems additionally read
+standard variables defined by third-party SDKs; those are listed at the end.
 
 This file documents the configuration options.
 
@@ -63,4 +64,18 @@ This file documents the configuration options.
 * **Used by:** {{range $i, $e := .UsedBy}}{{if $i}}, {{end}}{{$e}}{{end}}
 {{- end}}
 {{- end}}
+
+## Externally-provided configuration
+
+These are read by the AWS SDK, not by the node's own configuration layer, and
+apply only when CARTESI_AUTH_KIND=aws.
+
+* AWS_REGION / AWS_DEFAULT_REGION — region used to resolve the KMS key.
+* AWS_ENDPOINT_URL_KMS / AWS_ENDPOINT_URL — override the KMS endpoint
+  (VPC endpoint, PrivateLink, FIPS, or a local emulator such as LocalStack).
+* AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY / AWS_SESSION_TOKEN — static
+  credentials. They may instead come from the shared config file, an EC2 instance
+  profile, or IRSA; the node does not require any particular source.
+
+Full resolution order is documented by AWS; the node applies no overrides.
 `
diff --git a/internal/config/generated.go b/internal/config/generated.go
index cab15bdc8..a891a79f6 100644
--- a/internal/config/generated.go
+++ b/internal/config/generated.go
@@ -23,7 +23,6 @@ func init() {
 
 const (
 	AUTH_AWS_KMS_KEY_ID                               = "CARTESI_AUTH_AWS_KMS_KEY_ID"
-	AUTH_AWS_KMS_REGION                               = "CARTESI_AUTH_AWS_KMS_REGION"
 	AUTH_KIND                                         = "CARTESI_AUTH_KIND"
 	AUTH_MNEMONIC                                     = "CARTESI_AUTH_MNEMONIC"
 	AUTH_MNEMONIC_ACCOUNT_INDEX                       = "CARTESI_AUTH_MNEMONIC_ACCOUNT_INDEX"
@@ -102,8 +101,6 @@ func SetDefaults() {
 
 	// no default for CARTESI_AUTH_AWS_KMS_KEY_ID
 
-	// no default for CARTESI_AUTH_AWS_KMS_REGION
-
 	viper.SetDefault(AUTH_KIND, "mnemonic")
 
 	// no default for CARTESI_AUTH_MNEMONIC
@@ -1699,19 +1696,6 @@ func GetAuthAwsKmsKeyId() (RedactedString, error) {
 	return notDefinedRedactedString(), fmt.Errorf("%s: %w", AUTH_AWS_KMS_KEY_ID, ErrNotDefined)
 }
 
-// GetAuthAwsKmsRegion returns the value for the environment variable CARTESI_AUTH_AWS_KMS_REGION.
-func GetAuthAwsKmsRegion() (RedactedString, error) {
-	s := viper.GetString(AUTH_AWS_KMS_REGION)
-	if s != "" {
-		v, err := toRedactedString(s)
-		if err != nil {
-			return v, fmt.Errorf("failed to parse %s: %w", AUTH_AWS_KMS_REGION, err)
-		}
-		return v, nil
-	}
-	return notDefinedRedactedString(), fmt.Errorf("%s: %w", AUTH_AWS_KMS_REGION, ErrNotDefined)
-}
-
 // GetAuthKind returns the value for the environment variable CARTESI_AUTH_KIND.
 func GetAuthKind() (AuthKind, error) {
 	s := viper.GetString(AUTH_KIND)
diff --git a/internal/kms/signtx.go b/internal/kms/signtx.go
index 26446dae6..aad5d5c52 100644
--- a/internal/kms/signtx.go
+++ b/internal/kms/signtx.go
@@ -10,12 +10,13 @@
 package kms
 
 import (
+	"bytes"
 	"context"
 	"crypto/ecdsa"
 	"encoding/asn1"
 	"errors"
+	"fmt"
 	"math/big"
-	"reflect"
 
 	"github.com/aws/aws-sdk-go-v2/service/kms"
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
@@ -34,31 +35,33 @@ type Client interface {
 	Sign(context.Context, *kms.SignInput, ...func(*kms.Options)) (*kms.SignOutput, error)
 }
 
+const signatureComponentSize = 32
+
 /* AWS sometimes reply with a `r` larger than 32bytes padded on the left with
  * zeros. Trim it down to a total of 32bytes */
-func normalizeR(R []byte) ([]byte, error) {
-	if len(R) <= 32 {
-		return R, nil
+func normalizeR(r []byte) ([]byte, error) {
+	if len(r) <= signatureComponentSize {
+		return r, nil
 	}
-	for i := 0; i < len(R)-32; i++ {
-		if R[i] != 0 { // must be padding
+	for i := 0; i < len(r)-signatureComponentSize; i++ {
+		if r[i] != 0 { // must be padding
 			return nil, errors.New("malformed `r` component")
 		}
 	}
-	return R[len(R)-32:], nil
+	return r[len(r)-signatureComponentSize:], nil
 }
 
 /* normalize `s` to the lower half of N according to EIP-2
  * ref. https://eips.ethereum.org/EIPS/eip-2 */
-func normalizeS(S []byte) []byte {
-	N := crypto.S256().Params().N
-	halfN := new(big.Int).Div(N, big.NewInt(2)) //nolint:mnd
-	SBI := new(big.Int).SetBytes(S)
+func normalizeS(s []byte) []byte {
+	n := crypto.S256().Params().N
+	halfN := new(big.Int).Div(n, big.NewInt(2)) //nolint:mnd
+	sBigInt := new(big.Int).SetBytes(s)
 
-	if SBI.Cmp(halfN) > 0 {
-		S = new(big.Int).Sub(N, SBI).Bytes()
+	if sBigInt.Cmp(halfN) > 0 {
+		s = new(big.Int).Sub(n, sBigInt).Bytes()
 	}
-	return S
+	return s
 }
 
 /* Compute the final component `v` of the ethereum signature, one KMS doesn't
@@ -71,23 +74,27 @@ func normalizeS(S []byte) []byte {
  * of the values of `v` will hold ecrecover(hash, sig) == publicKey, and that
  * is the one ethereum wants. */
 func assembleSignature(r []byte, s []byte, hash []byte, key []byte) ([]byte, error) {
+	if len(r) > signatureComponentSize || len(s) > signatureComponentSize {
+		return nil, fmt.Errorf("malformed signature: len(r)=%d len(s)=%d", len(r), len(s))
+	}
+
 	sig := make([]byte, 65)
 
 	// align `s` and `r` in case they have less then 32bytes in size
-	copy(sig[32-len(r):], r)
+	copy(sig[signatureComponentSize-len(r):], r)
 	copy(sig[64-len(s):], s)
 
 	for i := byte(0); i < 2; i++ {
 		sig[64] = i
-		pub, err := crypto.Ecrecover(hash, sig[:])
+		pub, err := crypto.Ecrecover(hash, sig)
 		if err != nil {
-			return nil, err
+			continue
 		}
-		if reflect.DeepEqual(pub, key) {
+		if bytes.Equal(pub, key) {
 			return sig, nil
 		}
 	}
-	return sig, errors.New("failed to compute signature")
+	return nil, errors.New("failed to compute signature")
 }
 
 /* Create a SignTxFn that uses the KMS infrastructure from AWS for signing.
@@ -139,13 +146,13 @@ func CreateAWSSignTxFn(
 		if err != nil {
 			return nil, err
 		}
-		return tx.WithSignature(signer, signature[:])
+		return tx.WithSignature(signer, signature)
 	}, publicKey, crypto.PubkeyToAddress(*publicKey), nil
 }
 
-func GetPublicKeyBytes(ctx context.Context, client Client, Arn *string) ([]byte, error) {
+func GetPublicKeyBytes(ctx context.Context, client Client, arn *string) ([]byte, error) {
 	publicKeyOutput, err := client.GetPublicKey(ctx, &kms.GetPublicKeyInput{
-		KeyId: Arn,
+		KeyId: arn,
 	})
 	if err != nil {
 		return nil, err
diff --git a/internal/kms/signtx_test.go b/internal/kms/signtx_test.go
index a4d7d422d..bfa974d33 100644
--- a/internal/kms/signtx_test.go
+++ b/internal/kms/signtx_test.go
@@ -13,6 +13,7 @@ import (
 
 	"github.com/cartesi/rollups-node/pkg/ethutil"
 
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
 	ethtypes "github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
@@ -24,6 +25,8 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+const testKeyID = "alias/test-key"
+
 var ARN = ""
 
 /* Create a SignTxFn from a private key. Useful for testing */
@@ -33,18 +36,99 @@ func CreateSignTxFnFromPrivateKey(privateKey *ecdsa.PrivateKey) SignTxFn {
 	}
 }
 
+func TestAssembleSignatureRejectsOverlongComponents(t *testing.T) {
+	tests := []struct {
+		name     string
+		r        []byte
+		s        []byte
+		expected string
+	}{
+		{
+			name: "r", r: make([]byte, 33), s: make([]byte, 32),
+			expected: "malformed signature: len(r)=33 len(s)=32",
+		},
+		{
+			name: "s", r: make([]byte, 32), s: make([]byte, 33),
+			expected: "malformed signature: len(r)=32 len(s)=33",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			signature, err := assembleSignature(test.r, test.s, nil, nil)
+			require.Nil(t, signature)
+			require.EqualError(t, err, test.expected)
+		})
+	}
+}
+
+func TestNormalizeR(t *testing.T) {
+	t.Run("keeps components up to 32 bytes", func(t *testing.T) {
+		input := []byte{1, 2, 3}
+
+		r, err := normalizeR(input)
+		require.NoError(t, err)
+		require.Equal(t, input, r)
+	})
+
+	t.Run("trims leading zero padding", func(t *testing.T) {
+		padded := append([]byte{0}, make([]byte, 32)...)
+		padded[len(padded)-1] = 1
+
+		r, err := normalizeR(padded)
+		require.NoError(t, err)
+		require.Len(t, r, 32)
+		require.Equal(t, byte(1), r[len(r)-1])
+	})
+
+	t.Run("rejects non-padding bytes", func(t *testing.T) {
+		malformed := append([]byte{1}, make([]byte, 32)...)
+
+		r, err := normalizeR(malformed)
+		require.Nil(t, r)
+		require.EqualError(t, err, "malformed `r` component")
+	})
+}
+
+func TestNormalizeSConvertsHighSToLowS(t *testing.T) {
+	n := crypto.S256().Params().N
+	halfN := new(big.Int).Div(new(big.Int).Set(n), big.NewInt(2))
+	highS := new(big.Int).Add(halfN, big.NewInt(1))
+	expected := new(big.Int).Sub(n, highS).Bytes()
+
+	require.Equal(t, expected, normalizeS(highS.Bytes()))
+}
+
+func TestAssembleSignatureRejectsUnrecoverableKey(t *testing.T) {
+	privateKey, err := crypto.GenerateKey()
+	require.NoError(t, err)
+	otherKey, err := crypto.GenerateKey()
+	require.NoError(t, err)
+	hash := crypto.Keccak256([]byte("test transaction"))
+	signature, err := crypto.Sign(hash, privateKey)
+	require.NoError(t, err)
+
+	assembled, err := assembleSignature(
+		signature[:32], signature[32:64], hash, crypto.FromECDSAPub(&otherKey.PublicKey),
+	)
+	require.EqualError(t, err, "failed to compute signature")
+	require.Nil(t, assembled)
+}
+
+func TestAssembleSignatureTriesBothRecoveryIDs(t *testing.T) {
+	assembled, err := assembleSignature(make([]byte, 32), make([]byte, 32), make([]byte, 32), nil)
+	require.Nil(t, assembled)
+	require.EqualError(t, err, "failed to compute signature")
+}
+
 func sendFunds(
-	value *big.Int,
-	SignTx SignTxFn,
 	ctx context.Context,
+	client *ethclient.Client,
+	value *big.Int,
+	signTx SignTxFn,
 	sender common.Address,
 	recipient common.Address,
 ) {
-	client, err := ethclient.Dial("http://127.0.0.1:8545") // anvil
-	if err != nil {
-		panic(err)
-	}
-
 	nonce, err := client.PendingNonceAt(context.Background(), sender)
 	if err != nil {
 		panic(err)
@@ -55,12 +139,14 @@ func sendFunds(
 		panic(err)
 	}
 	var data []byte
-	tx := ethtypes.NewTransaction(nonce, recipient, value, gasLimit, gasPrice, data)
+	tx := ethtypes.NewTx(&ethtypes.LegacyTx{
+		Nonce: nonce, To: &recipient, Value: value, Gas: gasLimit, GasPrice: gasPrice, Data: data,
+	})
 	chainID, err := client.NetworkID(context.Background())
 	if err != nil {
 		panic(err)
 	}
-	signedTx, err := SignTx(ctx, tx, ethtypes.NewEIP155Signer(chainID))
+	signedTx, err := signTx(ctx, tx, ethtypes.LatestSignerForChainID(chainID))
 	if err != nil {
 		panic(err)
 	}
@@ -74,8 +160,13 @@ func TestSignTx(t *testing.T) {
 	if len(ARN) == 0 {
 		t.Skip("Skipping test, ARN for KMS key is unset")
 	}
-	value20 := big.NewInt(2000000000000000000) // in wei (2 eth)
-	value10 := big.NewInt(1000000000000000000) // in wei (1 eth)
+	value20 := big.NewInt(2000000000000000000)             // in wei (2 eth)
+	value10 := big.NewInt(1000000000000000000)             // in wei (1 eth)
+	client, err := ethclient.Dial("http://127.0.0.1:8545") // anvil
+	if err != nil {
+		panic(err)
+	}
+	defer client.Close()
 
 	anvilPrivateKey, err := ethutil.MnemonicToPrivateKey(ethutil.FoundryMnemonic, 0)
 	if err != nil {
@@ -94,10 +185,10 @@ func TestSignTx(t *testing.T) {
 		panic(err)
 	}
 
-	sendFunds(value20, CreateSignTxFnFromPrivateKey(anvilPrivateKey),
-		context.Background(), anvilAddress, KMSAddress)
-	sendFunds(value10, SignTx,
-		context.Background(), KMSAddress, anvilAddress)
+	sendFunds(context.Background(), client, value20, CreateSignTxFnFromPrivateKey(anvilPrivateKey),
+		anvilAddress, KMSAddress)
+	sendFunds(context.Background(), client, value10, SignTx,
+		KMSAddress, anvilAddress)
 }
 
 func TestAWSTransactOptsFactorySignsWithSubmitContext(t *testing.T) {
@@ -105,16 +196,17 @@ func TestAWSTransactOptsFactorySignsWithSubmitContext(t *testing.T) {
 	require.NoError(t, err)
 
 	client := newFakeKMSClient(t, privateKey)
-	arn := "alias/test-key"
+	arn := testKeyID
 	startupCtx, cancelStartup := context.WithCancel(context.Background())
 	factory, err := CreateAWSTransactOptsFactory(
 		startupCtx,
 		client,
 		&arn,
-		ethtypes.NewEIP155Signer(big.NewInt(1)),
+		ethtypes.LatestSignerForChainID(big.NewInt(1)),
 	)
 	require.NoError(t, err)
 	cancelStartup()
+	require.Equal(t, crypto.PubkeyToAddress(privateKey.PublicKey), factory.From())
 
 	type contextKey string
 	submitCtx := context.WithValue(context.Background(), contextKey("phase"), "submit")
@@ -128,11 +220,83 @@ func TestAWSTransactOptsFactorySignsWithSubmitContext(t *testing.T) {
 	require.NoError(t, client.signContext.Err())
 }
 
+func TestAWSTransactOptsFactoryRejectsUnauthorizedAddress(t *testing.T) {
+	privateKey, err := crypto.GenerateKey()
+	require.NoError(t, err)
+	client := newFakeKMSClient(t, privateKey)
+	arn := testKeyID
+	factory, err := CreateAWSTransactOptsFactory(
+		context.Background(), client, &arn, ethtypes.LatestSignerForChainID(big.NewInt(1)),
+	)
+	require.NoError(t, err)
+	opts, err := factory.NewTransactOpts(context.Background())
+	require.NoError(t, err)
+	tx := ethtypes.NewTransaction(0, common.Address{0x01}, big.NewInt(1), 21000, big.NewInt(1), nil)
+
+	signed, err := opts.Signer(common.Address{0xff}, tx)
+	require.Nil(t, signed)
+	require.ErrorIs(t, err, bind.ErrNotAuthorized)
+	require.Zero(t, client.signCalls)
+}
+
+func TestAWSSignTxRejectsNonCanonicalDERComponents(t *testing.T) {
+	privateKey, err := crypto.GenerateKey()
+	require.NoError(t, err)
+	arn := testKeyID
+	tx := ethtypes.NewTransaction(0, common.Address{0x01}, big.NewInt(1), 21000, big.NewInt(1), nil)
+	signer := ethtypes.LatestSignerForChainID(big.NewInt(1))
+
+	tests := []struct {
+		name     string
+		r        []byte
+		s        []byte
+		expected string
+	}{
+		{
+			name: "non-padding byte in overlong r", r: append([]byte{1}, make([]byte, 32)...), s: []byte{1},
+			expected: "malformed `r` component",
+		},
+		{
+			name: "non-minimal overlong s", r: []byte{1}, s: append([]byte{0}, make([]byte, 32)...),
+			expected: "malformed signature: len(r)=1 len(s)=33",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			client := newFakeKMSClient(t, privateKey)
+			client.signature = marshalRawECDSASignature(test.r, test.s)
+			signTx, _, _, err := CreateAWSSignTxFn(context.Background(), client, &arn)
+			require.NoError(t, err)
+
+			signed, err := signTx(context.Background(), tx, signer)
+			require.Nil(t, signed)
+			require.EqualError(t, err, test.expected)
+		})
+	}
+}
+
+func marshalRawECDSASignature(r, s []byte) []byte {
+	const maxDERLength = 255
+	if len(r) > maxDERLength || len(s) > maxDERLength || len(r)+len(s)+4 > maxDERLength {
+		panic("test DER signature is too large for single-byte length encoding")
+	}
+
+	content := make([]byte, 0, len(r)+len(s)+4)
+	content = append(content, 0x02, byte(len(r))) //nolint:gosec // Length is bounded above.
+	content = append(content, r...)
+	content = append(content, 0x02, byte(len(s))) //nolint:gosec // Length is bounded above.
+	content = append(content, s...)
+	return append([]byte{0x30, byte(len(content))}, content...) //nolint:gosec // Length is bounded above.
+}
+
 type fakeKMSClient struct {
 	t           *testing.T
 	privateKey  *ecdsa.PrivateKey
 	publicKey   []byte
 	signContext context.Context
+	signCalls   int
+	signature   []byte
 }
 
 func newFakeKMSClient(t *testing.T, privateKey *ecdsa.PrivateKey) *fakeKMSClient {
@@ -170,7 +334,11 @@ func (f *fakeKMSClient) Sign(
 	input *awskms.SignInput,
 	_ ...func(*awskms.Options),
 ) (*awskms.SignOutput, error) {
+	f.signCalls++
 	f.signContext = ctx
+	if f.signature != nil {
+		return &awskms.SignOutput{Signature: f.signature}, nil
+	}
 	r, s, err := ecdsa.Sign(rand.Reader, f.privateKey, input.Message)
 	require.NoError(f.t, err)
 	signature, err := asn1.Marshal(struct {
diff --git a/internal/node/node.go b/internal/node/node.go
index 872ca8c26..9954bd1c8 100644
--- a/internal/node/node.go
+++ b/internal/node/node.go
@@ -5,13 +5,18 @@ package node
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"log/slog"
+	"sync"
+	"time"
 
 	"github.com/cartesi/rollups-node/pkg/service"
 
 	"github.com/cartesi/rollups-node/internal/advancer"
 	"github.com/cartesi/rollups-node/internal/claimer"
 	"github.com/cartesi/rollups-node/internal/config"
+	"github.com/cartesi/rollups-node/internal/config/auth"
 	"github.com/cartesi/rollups-node/internal/evmreader"
 	"github.com/cartesi/rollups-node/internal/jsonrpc"
 	"github.com/cartesi/rollups-node/internal/prt"
@@ -26,8 +31,11 @@ import (
 type serviceResult struct {
 	service service.IService
 	err     error
+	create  serviceCreator
 }
 
+var degradedServiceRetryInterval = 5 * time.Second
+
 type CreateInfo struct {
 	service.CreateInfo
 
@@ -87,7 +95,7 @@ func createServices(ctx context.Context, c *CreateInfo, s *Service) error {
 	for _, create := range creators {
 		go func() {
 			svc, err := create(ctx, c, s)
-			ch <- serviceResult{service: svc, err: err}
+			ch <- serviceResult{service: svc, err: err, create: create}
 		}()
 	}
 
@@ -95,6 +103,15 @@ func createServices(ctx context.Context, c *CreateInfo, s *Service) error {
 		select {
 		case result := <-ch:
 			if result.err != nil {
+				if errors.Is(result.err, auth.ErrSignerUnavailable) {
+					s.Logger.Error("Signing service started in degraded state; retrying until the signer is available",
+						"error", result.err)
+					s.Children = append(s.Children, newDegradedService(ctx, s.Logger,
+						func(retryCtx context.Context) (service.IService, error) {
+							return result.create(retryCtx, c, s)
+						}))
+					continue
+				}
 				stopAndDrain(s.Children, ch, len(creators)-len(s.Children)-1)
 				return fmt.Errorf("failed to create service: %w", result.err)
 			}
@@ -107,6 +124,103 @@ func createServices(ctx context.Context, c *CreateInfo, s *Service) error {
 	return nil
 }
 
+// degradedService keeps a transiently unavailable signing service visible to
+// readiness checks while recreating it in the background. It becomes a thin
+// proxy once creation succeeds.
+type degradedService struct {
+	ctx    context.Context
+	cancel context.CancelFunc
+	logger *slog.Logger
+	create func(context.Context) (service.IService, error)
+
+	mu      sync.RWMutex
+	service service.IService
+}
+
+func newDegradedService(
+	ctx context.Context,
+	logger *slog.Logger,
+	create func(context.Context) (service.IService, error),
+) *degradedService {
+	retryCtx, cancel := context.WithCancel(ctx)
+	return &degradedService{ctx: retryCtx, cancel: cancel, logger: logger, create: create}
+}
+
+func (s *degradedService) current() service.IService {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	return s.service
+}
+
+func (s *degradedService) Alive() bool {
+	if child := s.current(); child != nil {
+		return child.Alive()
+	}
+	return true
+}
+
+func (s *degradedService) Ready() bool {
+	if child := s.current(); child != nil {
+		return child.Ready()
+	}
+	return false
+}
+
+func (s *degradedService) Reload() []error {
+	if child := s.current(); child != nil {
+		return child.Reload()
+	}
+	return nil
+}
+
+func (s *degradedService) Tick() []error { return nil }
+
+func (s *degradedService) Stop(force bool) []error {
+	s.cancel()
+	if child := s.current(); child != nil {
+		return child.Stop(force)
+	}
+	return nil
+}
+
+func (s *degradedService) String() string {
+	if child := s.current(); child != nil {
+		return child.String()
+	}
+	return "degraded signing service"
+}
+
+func (s *degradedService) Serve() error {
+	ticker := time.NewTicker(degradedServiceRetryInterval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-s.ctx.Done():
+			return nil
+		case <-ticker.C:
+			child, err := s.create(s.ctx)
+			if err != nil {
+				if s.ctx.Err() != nil {
+					return nil
+				}
+				s.logger.Error("Signing service remains degraded; creation retry failed", "error", err)
+				continue
+			}
+			if s.ctx.Err() != nil {
+				child.Stop(true)
+				return nil
+			}
+
+			s.mu.Lock()
+			s.service = child
+			s.mu.Unlock()
+			s.logger.Info("Signing service recovered")
+			return child.Serve()
+		}
+	}
+}
+
 // stopAndDrain stops already-created children and drains remaining results
 // from the channel, stopping any successful services to prevent resource leaks.
 func stopAndDrain(children []service.IService, ch <-chan serviceResult, remaining int) {
diff --git a/internal/node/node_test.go b/internal/node/node_test.go
new file mode 100644
index 000000000..2e2c5ca0c
--- /dev/null
+++ b/internal/node/node_test.go
@@ -0,0 +1,64 @@
+// (c) Cartesi and individual authors (see AUTHORS)
+// SPDX-License-Identifier: Apache-2.0 (see LICENSE)
+
+package node
+
+import (
+	"context"
+	"errors"
+	"io"
+	"log/slog"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/cartesi/rollups-node/pkg/service"
+	"github.com/stretchr/testify/require"
+)
+
+type recoveredService struct {
+	served  chan struct{}
+	stopped atomic.Bool
+}
+
+func (s *recoveredService) Alive() bool       { return true }
+func (s *recoveredService) Ready() bool       { return true }
+func (s *recoveredService) Reload() []error   { return nil }
+func (s *recoveredService) Tick() []error     { return nil }
+func (s *recoveredService) String() string    { return "recovered" }
+func (s *recoveredService) Stop(bool) []error { s.stopped.Store(true); return nil }
+func (s *recoveredService) Serve() error      { close(s.served); return nil }
+
+func TestDegradedServiceRetriesUntilRecovery(t *testing.T) {
+	oldInterval := degradedServiceRetryInterval
+	degradedServiceRetryInterval = time.Millisecond
+	t.Cleanup(func() { degradedServiceRetryInterval = oldInterval })
+
+	ctx, cancel := context.WithCancel(context.Background())
+	t.Cleanup(cancel)
+	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
+	recovered := &recoveredService{served: make(chan struct{})}
+	var attempts atomic.Int32
+	degraded := newDegradedService(ctx, logger, func(context.Context) (service.IService, error) {
+		if attempts.Add(1) < 2 {
+			return nil, errors.New("KMS unavailable")
+		}
+		return recovered, nil
+	})
+
+	require.True(t, degraded.Alive())
+	require.False(t, degraded.Ready())
+
+	done := make(chan error, 1)
+	go func() { done <- degraded.Serve() }()
+	select {
+	case <-recovered.served:
+	case <-time.After(time.Second):
+		t.Fatal("degraded service did not recover")
+	}
+
+	require.True(t, degraded.Ready())
+	require.NoError(t, <-done)
+	require.Empty(t, degraded.Stop(true))
+	require.True(t, recovered.stopped.Load())
+}
diff --git a/internal/prt/service.go b/internal/prt/service.go
index 9d9878886..64f228b28 100644
--- a/internal/prt/service.go
+++ b/internal/prt/service.go
@@ -50,8 +50,7 @@ type PersistentConfig struct {
 	ChainID                uint64
 }
 
-func Create(ctx context.Context, c *CreateInfo) (*Service, error) {
-	var err error
+func Create(ctx context.Context, c *CreateInfo) (_ *Service, err error) {
 	if err = ctx.Err(); err != nil {
 		return nil, err // This returns context.Canceled or context.DeadlineExceeded.
 	}
@@ -63,6 +62,11 @@ func Create(ctx context.Context, c *CreateInfo) (*Service, error) {
 	if err != nil {
 		return nil, err
 	}
+	defer func() {
+		if err != nil && s.Ticker != nil {
+			s.Ticker.Stop()
+		}
+	}()
 
 	if c.EthClient == nil {
 		return nil, fmt.Errorf("EthClient on prt service Create is nil")
@@ -121,6 +125,7 @@ func Create(ctx context.Context, c *CreateInfo) (*Service, error) {
 		if err != nil {
 			return nil, err
 		}
+		s.Logger.Info("PRT submitter identity", "address", s.txOptsFactory.From())
 	}
 
 	return s, nil