diff --git a/accounts/external/backend.go b/accounts/external/backend.go
index f6715a84e..b2de9e932 100644
--- a/accounts/external/backend.go
+++ b/accounts/external/backend.go
@@ -29,7 +29,7 @@ import (
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/rpc"
-	"github.com/ethereum/go-ethereum/signer/core"
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 )
 
 type ExternalBackend struct {
@@ -203,7 +203,7 @@ func (api *ExternalSigner) SignTx(account accounts.Account, tx *types.Transactio
 		t := common.NewMixedcaseAddress(*tx.To())
 		to = &t
 	}
-	args := &core.SendTxArgs{
+	args := &apitypes.SendTxArgs{
 		Data:  &data,
 		Nonce: hexutil.Uint64(tx.Nonce()),
 		Value: hexutil.Big(*tx.Value()),
diff --git a/cmd/abidump/main.go b/cmd/abidump/main.go
index 35cbcbb0e..4f942749d 100644
--- a/cmd/abidump/main.go
+++ b/cmd/abidump/main.go
@@ -23,7 +23,7 @@ import (
 	"os"
 	"strings"
 
-	"github.com/ethereum/go-ethereum/signer/core"
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 	"github.com/ethereum/go-ethereum/signer/fourbyte"
 )
 
@@ -41,7 +41,7 @@ func parse(data []byte) {
 	if err != nil {
 		die(err)
 	}
-	messages := core.ValidationMessages{}
+	messages := apitypes.ValidationMessages{}
 	db.ValidateCallData(nil, data, &messages)
 	for _, m := range messages.Messages {
 		fmt.Printf("%v: %v\n", m.Typ, m.Message)
diff --git a/cmd/clef/main.go b/cmd/clef/main.go
index 84e1dda99..cd2320518 100644
--- a/cmd/clef/main.go
+++ b/cmd/clef/main.go
@@ -50,10 +50,10 @@ import (
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/rpc"
 	"github.com/ethereum/go-ethereum/signer/core"
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 	"github.com/ethereum/go-ethereum/signer/fourbyte"
 	"github.com/ethereum/go-ethereum/signer/rules"
 	"github.com/ethereum/go-ethereum/signer/storage"
-
 	"github.com/mattn/go-colorable"
 	"github.com/mattn/go-isatty"
 	"gopkg.in/urfave/cli.v1"
@@ -923,7 +923,7 @@ func testExternalUI(api *core.SignerAPI) {
 		time.Sleep(delay)
 		data := hexutil.Bytes([]byte{})
 		to := common.NewMixedcaseAddress(a)
-		tx := core.SendTxArgs{
+		tx := apitypes.SendTxArgs{
 			Data:     &data,
 			Nonce:    0x1,
 			Value:    hexutil.Big(*big.NewInt(6)),
@@ -1055,11 +1055,11 @@ func GenDoc(ctx *cli.Context) {
 		data := hexutil.Bytes([]byte{0x01, 0x02, 0x03, 0x04})
 		add("SignTxRequest", desc, &core.SignTxRequest{
 			Meta: meta,
-			Callinfo: []core.ValidationInfo{
+			Callinfo: []apitypes.ValidationInfo{
 				{Typ: "Warning", Message: "Something looks odd, show this message as a warning"},
 				{Typ: "Info", Message: "User should see this as well"},
 			},
-			Transaction: core.SendTxArgs{
+			Transaction: apitypes.SendTxArgs{
 				Data:     &data,
 				Nonce:    0x1,
 				Value:    hexutil.Big(*big.NewInt(6)),
@@ -1075,7 +1075,7 @@ func GenDoc(ctx *cli.Context) {
 		add("SignTxResponse - approve", "Response to request to sign a transaction. This response needs to contain the `transaction`"+
 			", because the UI is free to make modifications to the transaction.",
 			&core.SignTxResponse{Approved: true,
-				Transaction: core.SendTxArgs{
+				Transaction: apitypes.SendTxArgs{
 					Data:     &data,
 					Nonce:    0x4,
 					Value:    hexutil.Big(*big.NewInt(6)),
diff --git a/signer/core/api.go b/signer/core/api.go
index 03daeeb6e..fb68018a6 100644
--- a/signer/core/api.go
+++ b/signer/core/api.go
@@ -33,6 +33,7 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/internal/ethapi"
 	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 	"github.com/ethereum/go-ethereum/signer/storage"
 )
 
@@ -52,7 +53,7 @@ type ExternalAPI interface {
 	// New request to create a new account
 	New(ctx context.Context) (common.Address, error)
 	// SignTransaction request to sign the specified transaction
-	SignTransaction(ctx context.Context, args SendTxArgs, methodSelector *string) (*ethapi.SignTransactionResult, error)
+	SignTransaction(ctx context.Context, args apitypes.SendTxArgs, methodSelector *string) (*ethapi.SignTransactionResult, error)
 	// SignData - request to sign the given data (plus prefix)
 	SignData(ctx context.Context, contentType string, addr common.MixedcaseAddress, data interface{}) (hexutil.Bytes, error)
 	// SignTypedData - request to sign the given structured data (plus prefix)
@@ -104,7 +105,7 @@ type Validator interface {
 	// ValidateTransaction does a number of checks on the supplied transaction, and
 	// returns either a list of warnings, or an error (indicating that the transaction
 	// should be immediately rejected).
-	ValidateTransaction(selector *string, tx *SendTxArgs) (*ValidationMessages, error)
+	ValidateTransaction(selector *string, tx *apitypes.SendTxArgs) (*apitypes.ValidationMessages, error)
 }
 
 // SignerAPI defines the actual implementation of ExternalAPI
@@ -220,24 +221,24 @@ func (m Metadata) String() string {
 type (
 	// SignTxRequest contains info about a Transaction to sign
 	SignTxRequest struct {
-		Transaction SendTxArgs       `json:"transaction"`
-		Callinfo    []ValidationInfo `json:"call_info"`
-		Meta        Metadata         `json:"meta"`
+		Transaction apitypes.SendTxArgs       `json:"transaction"`
+		Callinfo    []apitypes.ValidationInfo `json:"call_info"`
+		Meta        Metadata                  `json:"meta"`
 	}
 	// SignTxResponse result from SignTxRequest
 	SignTxResponse struct {
 		//The UI may make changes to the TX
-		Transaction SendTxArgs `json:"transaction"`
-		Approved    bool       `json:"approved"`
+		Transaction apitypes.SendTxArgs `json:"transaction"`
+		Approved    bool                `json:"approved"`
 	}
 	SignDataRequest struct {
-		ContentType string                  `json:"content_type"`
-		Address     common.MixedcaseAddress `json:"address"`
-		Rawdata     []byte                  `json:"raw_data"`
-		Messages    []*NameValueType        `json:"messages"`
-		Callinfo    []ValidationInfo        `json:"call_info"`
-		Hash        hexutil.Bytes           `json:"hash"`
-		Meta        Metadata                `json:"meta"`
+		ContentType string                    `json:"content_type"`
+		Address     common.MixedcaseAddress   `json:"address"`
+		Rawdata     []byte                    `json:"raw_data"`
+		Messages    []*NameValueType          `json:"messages"`
+		Callinfo    []apitypes.ValidationInfo `json:"call_info"`
+		Hash        hexutil.Bytes             `json:"hash"`
+		Meta        Metadata                  `json:"meta"`
 	}
 	SignDataResponse struct {
 		Approved bool `json:"approved"`
@@ -537,7 +538,7 @@ func (api *SignerAPI) lookupOrQueryPassword(address common.Address, title, promp
 }
 
 // SignTransaction signs the given Transaction and returns it both as json and rlp-encoded form
-func (api *SignerAPI) SignTransaction(ctx context.Context, args SendTxArgs, methodSelector *string) (*ethapi.SignTransactionResult, error) {
+func (api *SignerAPI) SignTransaction(ctx context.Context, args apitypes.SendTxArgs, methodSelector *string) (*ethapi.SignTransactionResult, error) {
 	var (
 		err    error
 		result SignTxResponse
@@ -548,7 +549,7 @@ func (api *SignerAPI) SignTransaction(ctx context.Context, args SendTxArgs, meth
 	}
 	// If we are in 'rejectMode', then reject rather than show the user warnings
 	if api.rejectMode {
-		if err := msgs.getWarnings(); err != nil {
+		if err := msgs.GetWarnings(); err != nil {
 			return nil, err
 		}
 	}
@@ -585,7 +586,7 @@ func (api *SignerAPI) SignTransaction(ctx context.Context, args SendTxArgs, meth
 		return nil, err
 	}
 	// Convert fields into a real transaction
-	var unsignedTx = result.Transaction.toTransaction()
+	var unsignedTx = result.Transaction.ToTransaction()
 	// Get the password for the transaction
 	pw, err := api.lookupOrQueryPassword(acc.Address, "Account password",
 		fmt.Sprintf("Please enter the password for account %s", acc.Address.String()))
@@ -621,7 +622,7 @@ func (api *SignerAPI) SignGnosisSafeTx(ctx context.Context, signerAddress common
 	}
 	// If we are in 'rejectMode', then reject rather than show the user warnings
 	if api.rejectMode {
-		if err := msgs.getWarnings(); err != nil {
+		if err := msgs.GetWarnings(); err != nil {
 			return nil, err
 		}
 	}
diff --git a/signer/core/api_test.go b/signer/core/api_test.go
index ff4d281d4..36f12f71a 100644
--- a/signer/core/api_test.go
+++ b/signer/core/api_test.go
@@ -35,6 +35,7 @@ import (
 	"github.com/ethereum/go-ethereum/internal/ethapi"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/signer/core"
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 	"github.com/ethereum/go-ethereum/signer/fourbyte"
 	"github.com/ethereum/go-ethereum/signer/storage"
 )
@@ -223,14 +224,14 @@ func TestNewAcc(t *testing.T) {
 	}
 }
 
-func mkTestTx(from common.MixedcaseAddress) core.SendTxArgs {
+func mkTestTx(from common.MixedcaseAddress) apitypes.SendTxArgs {
 	to := common.NewMixedcaseAddress(common.HexToAddress("0x1337"))
 	gas := hexutil.Uint64(21000)
 	gasPrice := (hexutil.Big)(*big.NewInt(2000000000))
 	value := (hexutil.Big)(*big.NewInt(1e18))
 	nonce := (hexutil.Uint64)(0)
 	data := hexutil.Bytes(common.Hex2Bytes("01020304050607080a"))
-	tx := core.SendTxArgs{
+	tx := apitypes.SendTxArgs{
 		From:     from,
 		To:       &to,
 		Gas:      gas,
diff --git a/signer/core/types.go b/signer/core/apitypes/types.go
similarity index 96%
rename from signer/core/types.go
rename to signer/core/apitypes/types.go
index 85ea6170d..591d253ab 100644
--- a/signer/core/types.go
+++ b/signer/core/apitypes/types.go
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
 
-package core
+package apitypes
 
 import (
 	"encoding/json"
@@ -52,7 +52,7 @@ func (vs *ValidationMessages) Info(msg string) {
 }
 
 /// getWarnings returns an error with all messages of type WARN of above, or nil if no warnings were present
-func (v *ValidationMessages) getWarnings() error {
+func (v *ValidationMessages) GetWarnings() error {
 	var messages []string
 	for _, msg := range v.Messages {
 		if msg.Typ == WARN || msg.Typ == CRIT {
@@ -97,7 +97,7 @@ func (args SendTxArgs) String() string {
 	return err.Error()
 }
 
-func (args *SendTxArgs) toTransaction() *types.Transaction {
+func (args *SendTxArgs) ToTransaction() *types.Transaction {
 	txArgs := ethapi.TransactionArgs{
 		Gas:                  &args.Gas,
 		GasPrice:             args.GasPrice,
diff --git a/signer/core/auditlog.go b/signer/core/auditlog.go
index bda88a8b2..84877ee71 100644
--- a/signer/core/auditlog.go
+++ b/signer/core/auditlog.go
@@ -24,6 +24,7 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/internal/ethapi"
 	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 )
 
 type AuditLogger struct {
@@ -43,7 +44,7 @@ func (l *AuditLogger) New(ctx context.Context) (common.Address, error) {
 	return l.api.New(ctx)
 }
 
-func (l *AuditLogger) SignTransaction(ctx context.Context, args SendTxArgs, methodSelector *string) (*ethapi.SignTransactionResult, error) {
+func (l *AuditLogger) SignTransaction(ctx context.Context, args apitypes.SendTxArgs, methodSelector *string) (*ethapi.SignTransactionResult, error) {
 	sel := "<nil>"
 	if methodSelector != nil {
 		sel = *methodSelector
diff --git a/signer/core/gnosis_safe.go b/signer/core/gnosis_safe.go
index 050425f0a..bdf7f837a 100644
--- a/signer/core/gnosis_safe.go
+++ b/signer/core/gnosis_safe.go
@@ -7,6 +7,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/common/math"
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 )
 
 // GnosisSafeTx is a type to parse the safe-tx returned by the relayer,
@@ -76,9 +77,9 @@ func (tx *GnosisSafeTx) ToTypedData() TypedData {
 
 // ArgsForValidation returns a SendTxArgs struct, which can be used for the
 // common validations, e.g. look up 4byte destinations
-func (tx *GnosisSafeTx) ArgsForValidation() *SendTxArgs {
+func (tx *GnosisSafeTx) ArgsForValidation() *apitypes.SendTxArgs {
 	gp := hexutil.Big(tx.GasPrice)
-	args := &SendTxArgs{
+	args := &apitypes.SendTxArgs{
 		From:     tx.Safe,
 		To:       &tx.To,
 		Gas:      hexutil.Uint64(tx.SafeTxGas.Uint64()),
diff --git a/signer/core/signed_data.go b/signer/core/signed_data.go
index 3bff1e1f2..6c2fd5f8f 100644
--- a/signer/core/signed_data.go
+++ b/signer/core/signed_data.go
@@ -38,6 +38,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 )
 
 type SigFormat struct {
@@ -323,7 +324,7 @@ func (api *SignerAPI) SignTypedData(ctx context.Context, addr common.MixedcaseAd
 // signTypedData is identical to the capitalized version, except that it also returns the hash (preimage)
 // - the signature preimage (hash)
 func (api *SignerAPI) signTypedData(ctx context.Context, addr common.MixedcaseAddress,
-	typedData TypedData, validationMessages *ValidationMessages) (hexutil.Bytes, hexutil.Bytes, error) {
+	typedData TypedData, validationMessages *apitypes.ValidationMessages) (hexutil.Bytes, hexutil.Bytes, error) {
 	domainSeparator, err := typedData.HashStruct("EIP712Domain", typedData.Domain.Map())
 	if err != nil {
 		return nil, nil, err
diff --git a/signer/fourbyte/validation.go b/signer/fourbyte/validation.go
index f311c89e5..58111e8e0 100644
--- a/signer/fourbyte/validation.go
+++ b/signer/fourbyte/validation.go
@@ -23,14 +23,14 @@ import (
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/signer/core"
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 )
 
 // ValidateTransaction does a number of checks on the supplied transaction, and
 // returns either a list of warnings, or an error (indicating that the transaction
 // should be immediately rejected).
-func (db *Database) ValidateTransaction(selector *string, tx *core.SendTxArgs) (*core.ValidationMessages, error) {
-	messages := new(core.ValidationMessages)
+func (db *Database) ValidateTransaction(selector *string, tx *apitypes.SendTxArgs) (*apitypes.ValidationMessages, error) {
+	messages := new(apitypes.ValidationMessages)
 
 	// Prevent accidental erroneous usage of both 'input' and 'data' (show stopper)
 	if tx.Data != nil && tx.Input != nil && !bytes.Equal(*tx.Data, *tx.Input) {
@@ -90,7 +90,7 @@ func (db *Database) ValidateTransaction(selector *string, tx *core.SendTxArgs) (
 
 // ValidateCallData checks if the ABI call-data + method selector (if given) can
 // be parsed and seems to match.
-func (db *Database) ValidateCallData(selector *string, data []byte, messages *core.ValidationMessages) {
+func (db *Database) ValidateCallData(selector *string, data []byte, messages *apitypes.ValidationMessages) {
 	// If the data is empty, we have a plain value transfer, nothing more to do
 	if len(data) == 0 {
 		return
diff --git a/signer/fourbyte/validation_test.go b/signer/fourbyte/validation_test.go
index b088cf309..c3085696f 100644
--- a/signer/fourbyte/validation_test.go
+++ b/signer/fourbyte/validation_test.go
@@ -22,7 +22,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
-	"github.com/ethereum/go-ethereum/signer/core"
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 )
 
 func mixAddr(a string) (*common.MixedcaseAddress, error) {
@@ -36,7 +36,7 @@ func toHexUint(h string) hexutil.Uint64 {
 	b := big.NewInt(0).SetBytes(common.FromHex(h))
 	return hexutil.Uint64(b.Uint64())
 }
-func dummyTxArgs(t txtestcase) *core.SendTxArgs {
+func dummyTxArgs(t txtestcase) *apitypes.SendTxArgs {
 	to, _ := mixAddr(t.to)
 	from, _ := mixAddr(t.from)
 	n := toHexUint(t.n)
@@ -55,7 +55,7 @@ func dummyTxArgs(t txtestcase) *core.SendTxArgs {
 		input = &a
 
 	}
-	return &core.SendTxArgs{
+	return &apitypes.SendTxArgs{
 		From:     *from,
 		To:       to,
 		Value:    value,
diff --git a/signer/rules/rules_test.go b/signer/rules/rules_test.go
index ec11e3712..d506ef2db 100644
--- a/signer/rules/rules_test.go
+++ b/signer/rules/rules_test.go
@@ -28,6 +28,7 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/internal/ethapi"
 	"github.com/ethereum/go-ethereum/signer/core"
+	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 	"github.com/ethereum/go-ethereum/signer/storage"
 )
 
@@ -180,7 +181,7 @@ func TestSignTxRequest(t *testing.T) {
 	}
 	t.Logf("to %v", to.Address().String())
 	resp, err := r.ApproveTx(&core.SignTxRequest{
-		Transaction: core.SendTxArgs{
+		Transaction: apitypes.SendTxArgs{
 			From: *from,
 			To:   to},
 		Callinfo: nil,
@@ -432,7 +433,7 @@ func dummyTx(value hexutil.Big) *core.SignTxRequest {
 	gasPrice := hexutil.Big(*big.NewInt(2000000))
 
 	return &core.SignTxRequest{
-		Transaction: core.SendTxArgs{
+		Transaction: apitypes.SendTxArgs{
 			From:     *from,
 			To:       to,
 			Value:    value,
@@ -440,7 +441,7 @@ func dummyTx(value hexutil.Big) *core.SignTxRequest {
 			GasPrice: &gasPrice,
 			Gas:      gas,
 		},
-		Callinfo: []core.ValidationInfo{
+		Callinfo: []apitypes.ValidationInfo{
 			{Typ: "Warning", Message: "All your base are bellong to us"},
 		},
 		Meta: core.Metadata{Remote: "remoteip", Local: "localip", Scheme: "inproc"},