diff --git a/conf/config.go b/conf/config.go
index b260cb19..c6eae482 100644
--- a/conf/config.go
+++ b/conf/config.go
@@ -134,6 +134,9 @@ type GatewayConfig struct {
 
 	// OasisRPCs controls whether to enable the `oasis_*` methods. Default is not exposed.
 	ExposeOasisRPCs bool `koanf:"oasis_rpcs"`
+
+	// AllowUnencryptedTxs also accepts transacions with CallFormat=0. Default is false.
+	AllowUnencryptedTxs bool `koanf:"allow_unencrypted_txs"`
 }
 
 // GatewayMonitoringConfig is the gateway prometheus configuration.
diff --git a/conf/server.yml b/conf/server.yml
index 23ac83a8..854ab66d 100644
--- a/conf/server.yml
+++ b/conf/server.yml
@@ -36,4 +36,5 @@ gateway:
     port: 9999
   method_limits:
     get_logs_max_rounds: 100
-  oasis_rpcs: false
+  oasis_rpcs: true
+  allow_unencrypted_txs: false
diff --git a/conf/tests-c10l.yml b/conf/tests-c10l.yml
new file mode 100644
index 00000000..9bcca53d
--- /dev/null
+++ b/conf/tests-c10l.yml
@@ -0,0 +1,38 @@
+runtime_id: "8000000000000000000000000000000000000000000000000000000000000000"
+node_address: "unix:/tmp/eth-runtime-test/net-runner/network/client-0/internal.sock"
+
+log:
+  level: debug
+  format: json
+
+cache:
+  block_size: 10
+  metrics: true
+
+database:
+  host: "127.0.0.1"
+  port: 5432
+  db: "postgres"
+  user: "postgres"
+  password: "postgres"
+  dial_timeout: 5
+  read_timeout: 10
+  write_timeout: 5
+  max_open_conns: 0
+
+gateway:
+  chain_id: 42262
+  http:
+    host: "localhost"
+    port: 8545
+  ws:
+    host: "localhost"
+    port: 8546
+  monitoring:
+    host: "localhost"
+    port: 9999
+  method_limits:
+    get_logs_max_rounds: 100
+  oasis_rpcs: true
+  allow_unencrypted_txs: false
+
diff --git a/rpc/apis.go b/rpc/apis.go
index 98c602f2..c649528f 100644
--- a/rpc/apis.go
+++ b/rpc/apis.go
@@ -34,7 +34,7 @@ func GetRPCAPIs(
 	var apis []ethRpc.API
 
 	web3Service := web3.NewPublicAPI()
-	ethService := eth.NewPublicAPI(client, archiveClient, logging.GetLogger("eth_rpc"), config.ChainID, backend, gasPriceOracle, config.MethodLimits)
+	ethService := eth.NewPublicAPI(client, archiveClient, logging.GetLogger("eth_rpc"), config.ChainID, backend, gasPriceOracle, config.MethodLimits, !config.ExposeOasisRPCs || config.AllowUnencryptedTxs)
 	netService := net.NewPublicAPI(config.ChainID)
 	txpoolService := txpool.NewPublicAPI()
 	filtersService := filters.NewPublicAPI(client, logging.GetLogger("eth_filters"), backend, eventSystem)
diff --git a/rpc/eth/api.go b/rpc/eth/api.go
index 143aa3d5..9e3f67ef 100644
--- a/rpc/eth/api.go
+++ b/rpc/eth/api.go
@@ -17,6 +17,7 @@ import (
 	"github.com/ethereum/go-ethereum/eth/filters"
 	"github.com/ethereum/go-ethereum/rlp"
 	ethrpc "github.com/ethereum/go-ethereum/rpc"
+	"github.com/oasisprotocol/oasis-core/go/common/cbor"
 	"github.com/oasisprotocol/oasis-core/go/common/logging"
 	"github.com/oasisprotocol/oasis-sdk/client-sdk/go/client"
 	"github.com/oasisprotocol/oasis-sdk/client-sdk/go/crypto/signature/secp256k1"
@@ -108,13 +109,14 @@ type API interface {
 }
 
 type publicAPI struct {
-	client         client.RuntimeClient
-	archiveClient  *archive.Client
-	backend        indexer.Backend
-	gasPriceOracle gas.Backend
-	chainID        uint32
-	Logger         *logging.Logger
-	methodLimits   *conf.MethodLimits
+	client              client.RuntimeClient
+	archiveClient       *archive.Client
+	backend             indexer.Backend
+	gasPriceOracle      gas.Backend
+	chainID             uint32
+	Logger              *logging.Logger
+	methodLimits        *conf.MethodLimits
+	allowUnencryptedTxs bool
 }
 
 // NewPublicAPI creates an instance of the public ETH Web3 API.
@@ -126,15 +128,17 @@ func NewPublicAPI(
 	backend indexer.Backend,
 	gasPriceOracle gas.Backend,
 	methodLimits *conf.MethodLimits,
+	allowUnencryptedTxes bool,
 ) API {
 	return &publicAPI{
-		client:         client,
-		archiveClient:  archiveClient,
-		chainID:        chainID,
-		Logger:         logger,
-		backend:        backend,
-		gasPriceOracle: gasPriceOracle,
-		methodLimits:   methodLimits,
+		client:              client,
+		archiveClient:       archiveClient,
+		chainID:             chainID,
+		Logger:              logger,
+		backend:             backend,
+		gasPriceOracle:      gasPriceOracle,
+		methodLimits:        methodLimits,
+		allowUnencryptedTxs: allowUnencryptedTxes,
 	}
 }
 
@@ -463,6 +467,13 @@ func (api *publicAPI) SendRawTransaction(ctx context.Context, data hexutil.Bytes
 		return common.Hash{}, ErrMalformedTransaction
 	}
 
+	if !api.checkOasisTxEncrypted(ethTx.Data()) {
+		logger.Debug("dropped unencrypted transaction", "hash", ethTx.Hash())
+		return common.Hash{}, ErrInvalidRequest
+	}
+
+	ethTx.Data()
+
 	// Generate an Ethereum transaction that is handled by the EVM module.
 	utx := types.UnverifiedTransaction{
 		Body: data,
@@ -751,3 +762,28 @@ func (api *publicAPI) getBlockRound(ctx context.Context, logger *logging.Logger,
 		return 0, nil
 	}
 }
+
+// checkOasisTxEncrypted checks, if the Oasis transaction wrapped inside Ethereum tx is encrypted.
+func (api *publicAPI) checkOasisTxEncrypted(data []byte) bool {
+	if api.allowUnencryptedTxs {
+		// Unencrypted transactions are allowed or encryption not supported by the gateway.
+		return true
+	}
+	if data == nil {
+		// Transaction is not Oasis transaction, ignore.
+		return true
+	}
+
+	var tx types.Transaction
+	if err := cbor.Unmarshal(data, &tx); err != nil {
+		// Transaction is not Oasis transaction, ignore.
+		return true
+	}
+
+	if tx.Call.Format == types.CallFormatPlain {
+		return false
+	}
+
+	// Transaction marked as encrypted.
+	return true
+}