diff --git a/eth/backend.go b/eth/backend.go
index e2b7fab1627cbb30fa782eab24558a9c3b2512f9..cba1b3939a2e893351090736c3d2da798b422979 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -45,6 +45,7 @@ import (
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/p2p/discover"
 	"github.com/ethereum/go-ethereum/p2p/nat"
+	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/whisper"
 )
 
@@ -370,8 +371,8 @@ func New(config *Config) (*Ethereum, error) {
 	eth.miner.SetGasPrice(config.GasPrice)
 
 	extra := config.Name
-	if len(extra) > 1024 {
-		extra = extra[:1024]
+	if uint64(len(extra)) > params.MaximumExtraDataSize.Uint64() {
+		extra = extra[:params.MaximumExtraDataSize.Uint64()]
 	}
 	eth.miner.SetExtra([]byte(extra))
 
diff --git a/params/protocol_params.go b/params/protocol_params.go
index 5c34abe8cd3e686fc6dcce778d20f19735f58ab7..684e06b7ecee6b57dc14c4506d06b358d244d33e 100755
--- a/params/protocol_params.go
+++ b/params/protocol_params.go
@@ -22,7 +22,7 @@ package params
 import "math/big"
 
 var (
-	MaximumExtraDataSize   = big.NewInt(1024)   // Maximum size extra data may be after Genesis.
+	MaximumExtraDataSize   = big.NewInt(32)     // Maximum size extra data may be after Genesis.
 	ExpByteGas             = big.NewInt(10)     // Times ceil(log256(exponent)) for the EXP instruction.
 	SloadGas               = big.NewInt(50)     // Multiplied by the number of 32-byte words that are copied (round up) for any *COPY operation and added.
 	CallValueTransferGas   = big.NewInt(9000)   // Paid for CALL when the value transfor is non-zero.
@@ -32,7 +32,7 @@ var (
 	DifficultyBoundDivisor = big.NewInt(2048)   // The bound divisor of the difficulty, used in the update calculations.
 	QuadCoeffDiv           = big.NewInt(512)    // Divisor for the quadratic particle of the memory cost equation.
 	GenesisDifficulty      = big.NewInt(131072) // Difficulty of the Genesis block.
-	DurationLimit          = big.NewInt(8)      // The decision boundary on the blocktime duration used to determine whether difficulty should go up or not.
+	DurationLimit          = big.NewInt(13)     // The decision boundary on the blocktime duration used to determine whether difficulty should go up or not.
 	SstoreSetGas           = big.NewInt(20000)  // Once per SLOAD operation.
 	LogDataGas             = big.NewInt(8)      // Per byte in a LOG* operation's data.
 	CallStipend            = big.NewInt(2300)   // Free gas given at beginning of call.
diff --git a/rpc/api/miner.go b/rpc/api/miner.go
index 93507f54a11d02b6a7269696ec9e4bd752c482b9..12203ffe0712eb401aff8aa0bf57ef4a8ff658bf 100644
--- a/rpc/api/miner.go
+++ b/rpc/api/miner.go
@@ -17,9 +17,12 @@
 package api
 
 import (
+	"fmt"
+
 	"github.com/ethereum/ethash"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/eth"
+	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rpc/codec"
 	"github.com/ethereum/go-ethereum/rpc/shared"
 )
@@ -122,6 +125,11 @@ func (self *minerApi) SetExtra(req *shared.Request) (interface{}, error) {
 	if err := self.codec.Decode(req.Params, &args); err != nil {
 		return nil, err
 	}
+
+	if uint64(len(args.Data)) > params.MaximumExtraDataSize.Uint64()*2 {
+		return false, fmt.Errorf("extra datasize can be no longer than %v bytes", params.MaximumExtraDataSize)
+	}
+
 	self.ethereum.Miner().SetExtra([]byte(args.Data))
 	return true, nil
 }