diff --git a/examples/basecoin/app/app_test.go b/examples/basecoin/app/app_test.go
index affa014155..148f0411fc 100644
--- a/examples/basecoin/app/app_test.go
+++ b/examples/basecoin/app/app_test.go
@@ -21,28 +21,16 @@ import (
 	"github.com/tendermint/tmlibs/log"
 )
 
-// helper variables and functions
-
+// Construct some global addrs and txs for tests.
 var (
-	// Construct genesis key/accounts
 	priv1 = crypto.GenPrivKeyEd25519()
 	addr1 = priv1.PubKey().Address()
 	addr2 = crypto.GenPrivKeyEd25519().PubKey().Address()
+	coins = sdk.Coins{{"foocoin", 10}}
 
 	sendMsg = bank.SendMsg{
-		Inputs: []bank.Input{
-			{
-				Address:  addr1,
-				Coins:    sdk.Coins{{"foocoin", 10}},
-				Sequence: 1,
-			},
-		},
-		Outputs: []bank.Output{
-			{
-				Address: addr2,
-				Coins:   sdk.Coins{{"foocoin", 10}},
-			},
-		},
+		Inputs:  []bank.Input{bank.NewInput(addr1, coins)},
+		Outputs: []bank.Output{bank.NewOutput(addr2, coins)},
 	}
 
 	whatCoolMsg1 = cool.WhatCoolMsg{
@@ -80,8 +68,10 @@ func TestMsgs(t *testing.T) {
 		{setWhatCoolMsg},
 	}
 
+	chainID := ""
+	sequences := []int64{0}
 	for i, m := range msgs {
-		sig := priv1.Sign(m.msg.GetSignBytes())
+		sig := priv1.Sign(sdk.StdSignBytes(chainID, sequences, m.msg))
 		tx := sdk.NewStdTx(m.msg, []sdk.StdSignature{{
 			PubKey:    priv1.PubKey(),
 			Signature: sig,
@@ -178,9 +168,12 @@ func TestSendMsgWithAccounts(t *testing.T) {
 	assert.Equal(t, acc1, res1)
 
 	// Sign the tx
+	chainID := "" // TODO: InitChain should get the ChainID
+	sequences := []int64{0}
+	sig := priv1.Sign(sdk.StdSignBytes(chainID, sequences, sendMsg))
 	tx := sdk.NewStdTx(sendMsg, []sdk.StdSignature{{
 		PubKey:    priv1.PubKey(),
-		Signature: priv1.Sign(sendMsg.GetSignBytes()),
+		Signature: sig,
 	}})
 
 	// Run a Check
@@ -198,6 +191,22 @@ func TestSendMsgWithAccounts(t *testing.T) {
 	res3 := bapp.accountMapper.GetAccount(ctxDeliver, addr2)
 	assert.Equal(t, fmt.Sprintf("%v", res2.GetCoins()), "67foocoin")
 	assert.Equal(t, fmt.Sprintf("%v", res3.GetCoins()), "10foocoin")
+
+	// Delivering again should cause replay error
+	res = bapp.Deliver(tx)
+	assert.Equal(t, sdk.CodeInvalidSequence, res.Code, res.Log)
+
+	// bumping the txnonce number without resigning should be an auth error
+	tx.Signatures[0].Sequence = 1
+	res = bapp.Deliver(tx)
+	assert.Equal(t, sdk.CodeUnauthorized, res.Code, res.Log)
+
+	// resigning the tx with the bumped sequence should work
+	sequences = []int64{1}
+	sig = priv1.Sign(sdk.StdSignBytes(chainID, sequences, tx.Msg))
+	tx.Signatures[0].Signature = sig
+	res = bapp.Deliver(tx)
+	assert.Equal(t, sdk.CodeOK, res.Code, res.Log)
 }
 
 //func TestWhatCoolMsg(t *testing.T) {
diff --git a/types/errors.go b/types/errors.go
index e52fe625f1..9d8175e309 100644
--- a/types/errors.go
+++ b/types/errors.go
@@ -22,12 +22,11 @@ const (
 	CodeOK                  CodeType = 0
 	CodeInternal            CodeType = 1
 	CodeTxParse             CodeType = 2
-	CodeBadNonce            CodeType = 3
+	CodeInvalidSequence     CodeType = 3
 	CodeUnauthorized        CodeType = 4
 	CodeInsufficientFunds   CodeType = 5
 	CodeUnknownRequest      CodeType = 6
 	CodeUnrecognizedAddress CodeType = 7
-	CodeInvalidSequence     CodeType = 8
 
 	CodeGenesisParse CodeType = 0xdead // TODO: remove ?
 )
@@ -41,8 +40,8 @@ func CodeToDefaultMsg(code CodeType) string {
 		return "Tx parse error"
 	case CodeGenesisParse:
 		return "Genesis parse error"
-	case CodeBadNonce:
-		return "Bad nonce"
+	case CodeInvalidSequence:
+		return "Invalid sequence"
 	case CodeUnauthorized:
 		return "Unauthorized"
 	case CodeInsufficientFunds:
@@ -51,8 +50,6 @@ func CodeToDefaultMsg(code CodeType) string {
 		return "Unknown request"
 	case CodeUnrecognizedAddress:
 		return "Unrecognized address"
-	case CodeInvalidSequence:
-		return "Invalid sequence"
 	default:
 		return fmt.Sprintf("Unknown code %d", code)
 	}
@@ -72,8 +69,8 @@ func ErrTxParse(msg string) Error {
 func ErrGenesisParse(msg string) Error {
 	return newError(CodeGenesisParse, msg)
 }
-func ErrBadNonce(msg string) Error {
-	return newError(CodeBadNonce, msg)
+func ErrInvalidSequence(msg string) Error {
+	return newError(CodeInvalidSequence, msg)
 }
 func ErrUnauthorized(msg string) Error {
 	return newError(CodeUnauthorized, msg)
@@ -87,9 +84,6 @@ func ErrUnknownRequest(msg string) Error {
 func ErrUnrecognizedAddress(addr Address) Error {
 	return newError(CodeUnrecognizedAddress, addr.String())
 }
-func ErrInvalidSequence(msg string) Error {
-	return newError(CodeInvalidSequence, msg)
-}
 
 //----------------------------------------
 // Error & sdkError
diff --git a/types/tx_msg.go b/types/tx_msg.go
index c6c96c364c..63f9347265 100644
--- a/types/tx_msg.go
+++ b/types/tx_msg.go
@@ -1,5 +1,7 @@
 package types
 
+import "encoding/json"
+
 // Transactions messages must fulfill the Msg
 type Msg interface {
 
@@ -66,7 +68,31 @@ func (tx StdTx) GetMsg() Msg                   { return tx.Msg }
 func (tx StdTx) GetFeePayer() Address          { return tx.Signatures[0].PubKey.Address() } // XXX but PubKey is optional!
 func (tx StdTx) GetSignatures() []StdSignature { return tx.Signatures }
 
-//__________________________________________________________
+// StdSignDoc is replay-prevention structure.
+// It includes the result of msg.GetSignBytes(),
+// as well as the ChainID (prevent cross chain replay)
+// and the Sequence numbers for each signature (prevent
+// inchain replay and enforce tx ordering per account).
+type StdSignDoc struct {
+	ChainID   string  `json:"chain_id"`
+	Sequences []int64 `json:"sequences"`
+	MsgBytes  []byte  `json:"msg_bytes"`
+	AltBytes  []byte  `json:"alt_bytes"` // TODO: do we really want this ?
+}
+
+func StdSignBytes(chainID string, sequences []int64, msg Msg) []byte {
+	bz, err := json.Marshal(StdSignDoc{
+		ChainID:   chainID,
+		Sequences: sequences,
+		MsgBytes:  msg.GetSignBytes(),
+	})
+	if err != nil {
+		panic(err)
+	}
+	return bz
+}
+
+//-------------------------------------
 
 // Application function variable used to unmarshal transaction bytes
 type TxDecoder func(txBytes []byte) (Tx, Error)
diff --git a/x/auth/ante.go b/x/auth/ante.go
index 11aa03c0d7..48e2344c6b 100644
--- a/x/auth/ante.go
+++ b/x/auth/ante.go
@@ -1,6 +1,8 @@
 package auth
 
 import (
+	"fmt"
+
 	sdk "github.com/cosmos/cosmos-sdk/types"
 )
 
@@ -9,82 +11,98 @@ func NewAnteHandler(accountMapper sdk.AccountMapper) sdk.AnteHandler {
 		ctx sdk.Context, tx sdk.Tx,
 	) (_ sdk.Context, _ sdk.Result, abort bool) {
 
-		// Deduct the fee from the fee payer.
-		// This is done first because it only
-		// requires fetching 1 account.
-		payerAddr := tx.GetFeePayer()
-		if payerAddr != nil {
-			payerAcc := accountMapper.GetAccount(ctx, payerAddr)
-			if payerAcc == nil {
-				return ctx,
-					sdk.ErrUnrecognizedAddress(payerAddr).Result(),
-					true
-			}
-			// TODO: Charge fee from payerAcc.
-			// TODO: accountMapper.SetAccount(ctx, payerAddr)
-		} else {
-			// TODO: Ensure that some other spam prevention is used.
-		}
-
-		var sigs = tx.GetSignatures()
-
 		// Assert that there are signatures.
+		var sigs = tx.GetSignatures()
 		if len(sigs) == 0 {
 			return ctx,
 				sdk.ErrUnauthorized("no signers").Result(),
 				true
 		}
 
-		// Ensure that sigs are correct.
-		var msg = tx.GetMsg()
-		var signerAddrs = msg.GetSigners()
-		var signerAccs = make([]sdk.Account, len(signerAddrs))
+		// TODO: can tx just implement message?
+		msg := tx.GetMsg()
 
 		// Assert that number of signatures is correct.
+		var signerAddrs = msg.GetSigners()
 		if len(sigs) != len(signerAddrs) {
 			return ctx,
 				sdk.ErrUnauthorized("wrong number of signers").Result(),
 				true
 		}
 
-		// Check each nonce and sig.
-		// TODO Refactor out.
-		for i, sig := range sigs {
+		// Collect accounts to set in the context
+		var signerAccs = make([]sdk.Account, len(signerAddrs))
 
-			var signerAcc = accountMapper.GetAccount(ctx, signerAddrs[i])
+		// Get the sign bytes by collecting all sequence numbers
+		sequences := make([]int64, len(signerAddrs))
+		for i := 0; i < len(signerAddrs); i++ {
+			sequences[i] = sigs[i].Sequence
+		}
+		signBytes := sdk.StdSignBytes(ctx.ChainID(), sequences, msg)
+
+		// Check fee payer sig and nonce, and deduct fee.
+		// This is done first because it only
+		// requires fetching 1 account.
+		payerAddr, payerSig := signerAddrs[0], sigs[0]
+		payerAcc, res := processSig(ctx, accountMapper, payerAddr, payerSig, signBytes)
+		if !res.IsOK() {
+			return ctx, res, true
+		}
+		signerAccs[0] = payerAcc
+		// TODO: Charge fee from payerAcc.
+		// TODO: accountMapper.SetAccount(ctx, payerAddr)
+
+		// Check sig and nonce for the rest.
+		for i := 1; i < len(sigs); i++ {
+			signerAddr, sig := signerAddrs[i], sigs[i]
+			signerAcc, res := processSig(ctx, accountMapper, signerAddr, sig, signBytes)
+			if !res.IsOK() {
+				return ctx, res, true
+			}
 			signerAccs[i] = signerAcc
-
-			// If no pubkey, set pubkey.
-			if signerAcc.GetPubKey().Empty() {
-				err := signerAcc.SetPubKey(sig.PubKey)
-				if err != nil {
-					return ctx,
-						sdk.ErrInternal("setting PubKey on signer").Result(),
-						true
-				}
-			}
-
-			// Check and increment sequence number.
-			seq := signerAcc.GetSequence()
-			if seq != sig.Sequence {
-				return ctx,
-					sdk.ErrInvalidSequence("").Result(),
-					true
-			}
-			signerAcc.SetSequence(seq + 1)
-
-			// Check sig.
-			if !sig.PubKey.VerifyBytes(msg.GetSignBytes(), sig.Signature) {
-				return ctx,
-					sdk.ErrUnauthorized("").Result(),
-					true
-			}
-
-			// Save the account.
-			accountMapper.SetAccount(ctx, signerAcc)
 		}
 
 		ctx = WithSigners(ctx, signerAccs)
 		return ctx, sdk.Result{}, false // continue...
 	}
 }
+
+// verify the signature and increment the sequence.
+// if the account doesn't have a pubkey, set it as well.
+func processSig(ctx sdk.Context, am sdk.AccountMapper, addr sdk.Address, sig sdk.StdSignature, signBytes []byte) (acc sdk.Account, res sdk.Result) {
+
+	// Get the account
+	acc = am.GetAccount(ctx, addr)
+	if acc == nil {
+		return nil, sdk.ErrUnrecognizedAddress(addr).Result()
+	}
+
+	// Check and increment sequence number.
+	seq := acc.GetSequence()
+	if seq != sig.Sequence {
+		return nil, sdk.ErrInvalidSequence(
+			fmt.Sprintf("Invalid sequence. Got %d, expected %d", sig.Sequence, seq)).Result()
+	}
+	acc.SetSequence(seq + 1)
+
+	// Check and possibly set pubkey.
+	pubKey := acc.GetPubKey()
+	if pubKey.Empty() {
+		pubKey = sig.PubKey
+		err := acc.SetPubKey(pubKey)
+		if err != nil {
+			return nil, sdk.ErrInternal("setting PubKey on signer").Result()
+		}
+	}
+	// TODO: should we enforce pubKey == sig.PubKey ?
+	// If not, ppl can send useless PubKeys after first tx
+
+	// Check sig.
+	if !sig.PubKey.VerifyBytes(signBytes, sig.Signature) {
+		return nil, sdk.ErrUnauthorized("signature verification failed").Result()
+	}
+
+	// Save the account.
+	am.SetAccount(ctx, acc)
+	return
+}
diff --git a/x/auth/ante_test.go b/x/auth/ante_test.go
new file mode 100644
index 0000000000..17ea204d31
--- /dev/null
+++ b/x/auth/ante_test.go
@@ -0,0 +1,163 @@
+package auth
+
+import (
+	"testing"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/stretchr/testify/assert"
+	abci "github.com/tendermint/abci/types"
+	crypto "github.com/tendermint/go-crypto"
+)
+
+// msg type for testing
+type testMsg struct {
+	signBytes []byte
+	signers   []sdk.Address
+}
+
+func newTestMsg(addrs ...sdk.Address) *testMsg {
+	return &testMsg{
+		signBytes: []byte("some sign bytes"),
+		signers:   addrs,
+	}
+}
+
+func (msg *testMsg) Type() string                            { return "testMsg" }
+func (msg *testMsg) Get(key interface{}) (value interface{}) { return nil }
+func (msg *testMsg) GetSignBytes() []byte {
+	return msg.signBytes
+}
+func (msg *testMsg) ValidateBasic() sdk.Error { return nil }
+func (msg *testMsg) GetSigners() []sdk.Address {
+	return msg.signers
+}
+
+// generate a priv key and return it with its address
+func privAndAddr() (crypto.PrivKey, sdk.Address) {
+	priv := crypto.GenPrivKeyEd25519()
+	addr := priv.PubKey().Address()
+	return priv.Wrap(), addr
+}
+
+// run the tx through the anteHandler and ensure its valid
+func checkValidTx(t *testing.T, anteHandler sdk.AnteHandler, ctx sdk.Context, tx sdk.Tx) {
+	_, result, abort := anteHandler(ctx, tx)
+	assert.False(t, abort)
+	assert.Equal(t, sdk.CodeOK, result.Code)
+	assert.True(t, result.IsOK())
+}
+
+// run the tx through the anteHandler and ensure it fails with the given code
+func checkInvalidTx(t *testing.T, anteHandler sdk.AnteHandler, ctx sdk.Context, tx sdk.Tx, code sdk.CodeType) {
+	_, result, abort := anteHandler(ctx, tx)
+	assert.True(t, abort)
+	assert.Equal(t, code, result.Code)
+}
+
+func newTestTx(ctx sdk.Context, msg sdk.Msg, privs []crypto.PrivKey, seqs []int64) sdk.Tx {
+	signBytes := sdk.StdSignBytes(ctx.ChainID(), seqs, msg)
+	sigs := make([]sdk.StdSignature, len(privs))
+	for i, priv := range privs {
+		sigs[i] = sdk.StdSignature{PubKey: priv.PubKey(), Signature: priv.Sign(signBytes), Sequence: seqs[i]}
+	}
+	return sdk.NewStdTx(msg, sigs)
+}
+
+// Test various error cases in the AnteHandler control flow.
+func TestAnteHandlerSigErrors(t *testing.T) {
+	// setup
+	ms, capKey := setupMultiStore()
+	mapper := NewAccountMapper(capKey, &BaseAccount{})
+	anteHandler := NewAnteHandler(mapper)
+	ctx := sdk.NewContext(ms, abci.Header{ChainID: "mychainid"}, false, nil)
+
+	// keys and addresses
+	priv1, addr1 := privAndAddr()
+	priv2, addr2 := privAndAddr()
+
+	// msg and signatures
+	var tx sdk.Tx
+	msg := newTestMsg(addr1, addr2)
+	tx = newTestTx(ctx, msg, []crypto.PrivKey{priv1, priv2}, []int64{0, 0})
+
+	// test no signatures
+	tx = newTestTx(ctx, msg, []crypto.PrivKey{}, []int64{})
+	checkInvalidTx(t, anteHandler, ctx, tx, sdk.CodeUnauthorized)
+
+	// test num sigs dont match GetSigners
+	tx = newTestTx(ctx, msg, []crypto.PrivKey{priv1}, []int64{0})
+	checkInvalidTx(t, anteHandler, ctx, tx, sdk.CodeUnauthorized)
+
+	// test an unrecognized account
+	tx = newTestTx(ctx, msg, []crypto.PrivKey{priv1, priv2}, []int64{0, 0})
+	checkInvalidTx(t, anteHandler, ctx, tx, sdk.CodeUnrecognizedAddress)
+
+	// save the first account, but second is still unrecognized
+	acc1 := mapper.NewAccountWithAddress(ctx, addr1)
+	mapper.SetAccount(ctx, acc1)
+	checkInvalidTx(t, anteHandler, ctx, tx, sdk.CodeUnrecognizedAddress)
+}
+
+// Test logic around sequence checking with one signer and many signers.
+func TestAnteHandlerSequences(t *testing.T) {
+	// setup
+	ms, capKey := setupMultiStore()
+	mapper := NewAccountMapper(capKey, &BaseAccount{})
+	anteHandler := NewAnteHandler(mapper)
+	ctx := sdk.NewContext(ms, abci.Header{ChainID: "mychainid"}, false, nil)
+
+	// keys and addresses
+	priv1, addr1 := privAndAddr()
+	priv2, addr2 := privAndAddr()
+
+	// set the accounts
+	acc1 := mapper.NewAccountWithAddress(ctx, addr1)
+	mapper.SetAccount(ctx, acc1)
+	acc2 := mapper.NewAccountWithAddress(ctx, addr2)
+	mapper.SetAccount(ctx, acc2)
+
+	// msg and signatures
+	var tx sdk.Tx
+	msg := newTestMsg(addr1)
+	tx = newTestTx(ctx, msg, []crypto.PrivKey{priv1}, []int64{0})
+
+	// test good tx from one signer
+	checkValidTx(t, anteHandler, ctx, tx)
+
+	// test sending it again fails (replay protection)
+	checkInvalidTx(t, anteHandler, ctx, tx, sdk.CodeInvalidSequence)
+
+	// fix sequence, should pass
+	tx = newTestTx(ctx, msg, []crypto.PrivKey{priv1}, []int64{1})
+	checkValidTx(t, anteHandler, ctx, tx)
+
+	// new tx with another signer and correct sequences
+	msg = newTestMsg(addr1, addr2)
+	tx = newTestTx(ctx, msg, []crypto.PrivKey{priv1, priv2}, []int64{2, 0})
+	checkValidTx(t, anteHandler, ctx, tx)
+
+	// replay fails
+	checkInvalidTx(t, anteHandler, ctx, tx, sdk.CodeInvalidSequence)
+
+	// tx from just second signer with incorrect sequence fails
+	msg = newTestMsg(addr2)
+	tx = newTestTx(ctx, msg, []crypto.PrivKey{priv2}, []int64{0})
+	checkInvalidTx(t, anteHandler, ctx, tx, sdk.CodeInvalidSequence)
+
+	// fix the sequence and it passes
+	tx = newTestTx(ctx, msg, []crypto.PrivKey{priv2}, []int64{1})
+	checkValidTx(t, anteHandler, ctx, tx)
+
+	// another tx from both of them that passes
+	msg = newTestMsg(addr1, addr2)
+	tx = newTestTx(ctx, msg, []crypto.PrivKey{priv1, priv2}, []int64{3, 2})
+	checkValidTx(t, anteHandler, ctx, tx)
+}
+
+func TestAnteHandlerBadSignBytes(t *testing.T) {
+	// TODO: test various cases of bad sign bytes
+}
+
+func TestAnteHandlerSetPubKey(t *testing.T) {
+	// TODO: test cases where pubkey is already set on the account
+}
diff --git a/x/auth/mapper.go b/x/auth/mapper.go
index b50e4405fd..1176db3cbe 100644
--- a/x/auth/mapper.go
+++ b/x/auth/mapper.go
@@ -11,6 +11,9 @@ import (
 	wire "github.com/cosmos/cosmos-sdk/wire"
 )
 
+var _ sdk.AccountMapper = (*accountMapper)(nil)
+var _ sdk.AccountMapper = (*sealedAccountMapper)(nil)
+
 // Implements sdk.AccountMapper.
 // This AccountMapper encodes/decodes accounts using the
 // go-wire (binary) encoding/decoding library.
@@ -108,6 +111,7 @@ func (sam sealedAccountMapper) WireCodec() *wire.Codec {
 //----------------------------------------
 // misc.
 
+// NOTE: currently unused
 func (am accountMapper) clonePrototypePtr() interface{} {
 	protoRt := reflect.TypeOf(am.proto)
 	if protoRt.Kind() == reflect.Ptr {
diff --git a/x/auth/mapper_test.go b/x/auth/mapper_test.go
new file mode 100644
index 0000000000..4ac96c3810
--- /dev/null
+++ b/x/auth/mapper_test.go
@@ -0,0 +1,81 @@
+package auth
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	abci "github.com/tendermint/abci/types"
+	crypto "github.com/tendermint/go-crypto"
+	oldwire "github.com/tendermint/go-wire"
+	dbm "github.com/tendermint/tmlibs/db"
+
+	"github.com/cosmos/cosmos-sdk/store"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+func setupMultiStore() (sdk.MultiStore, *sdk.KVStoreKey) {
+	db := dbm.NewMemDB()
+	capKey := sdk.NewKVStoreKey("capkey")
+	ms := store.NewCommitMultiStore(db)
+	ms.MountStoreWithDB(capKey, sdk.StoreTypeIAVL, db)
+	ms.LoadLatestVersion()
+
+	// wire registration while we're at it ... TODO
+	var _ = oldwire.RegisterInterface(
+		struct{ sdk.Account }{},
+		oldwire.ConcreteType{&BaseAccount{}, 0x1},
+	)
+
+	return ms, capKey
+}
+
+func TestAccountMapperGetSet(t *testing.T) {
+	ms, capKey := setupMultiStore()
+
+	// make context and mapper
+	ctx := sdk.NewContext(ms, abci.Header{}, false, nil)
+	mapper := NewAccountMapper(capKey, &BaseAccount{})
+
+	addr := sdk.Address([]byte("some-address"))
+
+	// no account before its created
+	acc := mapper.GetAccount(ctx, addr)
+	assert.Nil(t, acc)
+
+	// create account and check default values
+	acc = mapper.NewAccountWithAddress(ctx, addr)
+	assert.NotNil(t, acc)
+	assert.Equal(t, addr, acc.GetAddress())
+	assert.EqualValues(t, crypto.PubKey{}, acc.GetPubKey())
+	assert.EqualValues(t, 0, acc.GetSequence())
+
+	// NewAccount doesn't call Set, so it's still nil
+	assert.Nil(t, mapper.GetAccount(ctx, addr))
+
+	// set some values on the account and save it
+	newSequence := int64(20)
+	acc.SetSequence(newSequence)
+	mapper.SetAccount(ctx, acc)
+
+	// check the new values
+	acc = mapper.GetAccount(ctx, addr)
+	assert.NotNil(t, acc)
+	assert.Equal(t, newSequence, acc.GetSequence())
+}
+
+func TestAccountMapperSealed(t *testing.T) {
+	_, capKey := setupMultiStore()
+
+	// normal mapper exposes the wire codec
+	mapper := NewAccountMapper(capKey, &BaseAccount{})
+	assert.NotNil(t, mapper.WireCodec())
+
+	// seal mapper, should panic when we try to get the codec
+	mapperSealed := mapper.Seal()
+	assert.Panics(t, func() { mapperSealed.WireCodec() })
+
+	// another way to get a sealed mapper
+	mapperSealed = NewAccountMapperSealed(capKey, &BaseAccount{})
+	assert.Panics(t, func() { mapperSealed.WireCodec() })
+}
diff --git a/x/bank/tx.go b/x/bank/tx.go
index eef2a087d0..58af937210 100644
--- a/x/bank/tx.go
+++ b/x/bank/tx.go
@@ -4,8 +4,6 @@ import (
 	"encoding/json"
 	"fmt"
 
-	crypto "github.com/tendermint/go-crypto"
-
 	sdk "github.com/cosmos/cosmos-sdk/types"
 )
 
@@ -142,11 +140,8 @@ func (msg IssueMsg) GetSigners() []sdk.Address {
 
 // Transaction Output
 type Input struct {
-	Address  sdk.Address `json:"address"`
-	Coins    sdk.Coins   `json:"coins"`
-	Sequence int64       `json:"sequence"`
-
-	signature crypto.Signature
+	Address sdk.Address `json:"address"`
+	Coins   sdk.Coins   `json:"coins"`
 }
 
 // ValidateBasic - validate transaction input
@@ -154,9 +149,6 @@ func (in Input) ValidateBasic() sdk.Error {
 	if len(in.Address) == 0 {
 		return ErrInvalidAddress(in.Address.String())
 	}
-	if in.Sequence < 0 {
-		return ErrInvalidSequence("negative sequence")
-	}
 	if !in.Coins.IsValid() {
 		return ErrInvalidCoins(in.Coins.String())
 	}
@@ -179,13 +171,6 @@ func NewInput(addr sdk.Address, coins sdk.Coins) Input {
 	return input
 }
 
-// NewInputWithSequence - create a transaction input, used with SendMsg
-func NewInputWithSequence(addr sdk.Address, coins sdk.Coins, seq int64) Input {
-	input := NewInput(addr, coins)
-	input.Sequence = seq
-	return input
-}
-
 //----------------------------------------
 // Output
 
diff --git a/x/bank/tx_test.go b/x/bank/tx_test.go
index 099e81dbf4..bbfdc62ffd 100644
--- a/x/bank/tx_test.go
+++ b/x/bank/tx_test.go
@@ -13,20 +13,12 @@ func TestNewSendMsg(t *testing.T) {}
 
 func TestSendMsgType(t *testing.T) {
 	// Construct a SendMsg
+	addr1 := sdk.Address([]byte("input"))
+	addr2 := sdk.Address([]byte("output"))
+	coins := sdk.Coins{{"atom", 10}}
 	var msg = SendMsg{
-		Inputs: []Input{
-			{
-				Address:  sdk.Address([]byte("input")),
-				Coins:    sdk.Coins{{"atom", 10}},
-				Sequence: 1,
-			},
-		},
-		Outputs: []Output{
-			{
-				Address: sdk.Address([]byte("output")),
-				Coins:   sdk.Coins{{"atom", 10}},
-			},
-		},
+		Inputs:  []Input{NewInput(addr1, coins)},
+		Outputs: []Output{NewOutput(addr2, coins)},
 	}
 
 	// TODO some failures for bad result
@@ -53,18 +45,16 @@ func TestInputValidation(t *testing.T) {
 	}{
 		// auth works with different apps
 		{true, NewInput(addr1, someCoins)},
-		{true, NewInputWithSequence(addr1, someCoins, 100)},
-		{true, NewInputWithSequence(addr2, someCoins, 100)},
-		{true, NewInputWithSequence(addr2, multiCoins, 100)},
+		{true, NewInput(addr2, someCoins)},
+		{true, NewInput(addr2, multiCoins)},
 
-		{false, NewInput(emptyAddr, someCoins)},             // empty address
-		{false, NewInputWithSequence(addr1, someCoins, -1)}, // negative sequence
-		{false, NewInput(addr1, emptyCoins)},                // invalid coins
-		{false, NewInput(addr1, emptyCoins2)},               // invalid coins
-		{false, NewInput(addr1, someEmptyCoins)},            // invalid coins
-		{false, NewInput(addr1, minusCoins)},                // negative coins
-		{false, NewInput(addr1, someMinusCoins)},            // negative coins
-		{false, NewInput(addr1, unsortedCoins)},             // unsorted coins
+		{false, NewInput(emptyAddr, someCoins)},  // empty address
+		{false, NewInput(addr1, emptyCoins)},     // invalid coins
+		{false, NewInput(addr1, emptyCoins2)},    // invalid coins
+		{false, NewInput(addr1, someEmptyCoins)}, // invalid coins
+		{false, NewInput(addr1, minusCoins)},     // negative coins
+		{false, NewInput(addr1, someMinusCoins)}, // negative coins
+		{false, NewInput(addr1, unsortedCoins)},  // unsorted coins
 	}
 
 	for i, tc := range cases {
@@ -144,7 +134,7 @@ func TestSendMsgValidation(t *testing.T) {
 		{false, SendMsg{Inputs: []Input{input1}}},    // just input
 		{false, SendMsg{Outputs: []Output{output1}}}, // just ouput
 		{false, SendMsg{
-			Inputs:  []Input{NewInputWithSequence(emptyAddr, atom123, 1)}, // invalid input
+			Inputs:  []Input{NewInput(emptyAddr, atom123)}, // invalid input
 			Outputs: []Output{output1}}},
 		{false, SendMsg{
 			Inputs:  []Input{input1},
@@ -189,82 +179,54 @@ func TestSendMsgValidation(t *testing.T) {
 
 func TestSendMsgString(t *testing.T) {
 	// Construct a SendMsg
+	addr1 := sdk.Address([]byte("input"))
+	addr2 := sdk.Address([]byte("output"))
+	coins := sdk.Coins{{"atom", 10}}
 	var msg = SendMsg{
-		Inputs: []Input{
-			{
-				Address:  sdk.Address([]byte("input")),
-				Coins:    sdk.Coins{{"atom", 10}},
-				Sequence: 1,
-			},
-		},
-		Outputs: []Output{
-			{
-				Address: sdk.Address([]byte("output")),
-				Coins:   sdk.Coins{{"atom", 10}},
-			},
-		},
+		Inputs:  []Input{NewInput(addr1, coins)},
+		Outputs: []Output{NewOutput(addr2, coins)},
 	}
+
 	res := msg.String()
 	// TODO some failures for bad results
 	assert.Equal(t, res, "SendMsg{[Input{696E707574,10atom}]->[Output{364637353734373037353734,10atom}]}")
 }
 
 func TestSendMsgGet(t *testing.T) {
+	addr1 := sdk.Address([]byte("input"))
+	addr2 := sdk.Address([]byte("output"))
+	coins := sdk.Coins{{"atom", 10}}
 	var msg = SendMsg{
-		Inputs: []Input{
-			{
-				Address:  sdk.Address([]byte("input")),
-				Coins:    sdk.Coins{{"atom", 10}},
-				Sequence: 1,
-			},
-		},
-		Outputs: []Output{
-			{
-				Address: sdk.Address([]byte("output")),
-				Coins:   sdk.Coins{{"atom", 10}},
-			},
-		},
+		Inputs:  []Input{NewInput(addr1, coins)},
+		Outputs: []Output{NewOutput(addr2, coins)},
 	}
 	res := msg.Get(nil)
 	assert.Nil(t, res)
 }
 
 func TestSendMsgGetSignBytes(t *testing.T) {
+	addr1 := sdk.Address([]byte("input"))
+	addr2 := sdk.Address([]byte("output"))
+	coins := sdk.Coins{{"atom", 10}}
 	var msg = SendMsg{
-		Inputs: []Input{
-			{
-				Address:  sdk.Address([]byte("input")),
-				Coins:    sdk.Coins{{"atom", 10}},
-				Sequence: 1,
-			},
-		},
-		Outputs: []Output{
-			{
-				Address: sdk.Address([]byte("output")),
-				Coins:   sdk.Coins{{"atom", 10}},
-			},
-		},
+		Inputs:  []Input{NewInput(addr1, coins)},
+		Outputs: []Output{NewOutput(addr2, coins)},
 	}
 	res := msg.GetSignBytes()
 	// TODO bad results
-	assert.Equal(t, string(res), `{"inputs":[{"address":"696E707574","coins":[{"denom":"atom","amount":10}],"sequence":1}],"outputs":[{"address":"6F7574707574","coins":[{"denom":"atom","amount":10}]}]}`)
+	assert.Equal(t, string(res), `{"inputs":[{"address":"696E707574","coins":[{"denom":"atom","amount":10}]}],"outputs":[{"address":"6F7574707574","coins":[{"denom":"atom","amount":10}]}]}`)
 }
 
 func TestSendMsgGetSigners(t *testing.T) {
 	var msg = SendMsg{
 		Inputs: []Input{
-			{
-				Address: sdk.Address([]byte("input1")),
-			},
-			{
-				Address: sdk.Address([]byte("input2")),
-			},
-			{
-				Address: sdk.Address([]byte("input3")),
-			},
+			NewInput(sdk.Address([]byte("input1")), nil),
+			NewInput(sdk.Address([]byte("input2")), nil),
+			NewInput(sdk.Address([]byte("input3")), nil),
 		},
 	}
 	res := msg.GetSigners()
+	// TODO: fix this !
 	assert.Equal(t, fmt.Sprintf("%v", res), "[696E70757431 696E70757432 696E70757433]")
 }
 
@@ -297,14 +259,11 @@ func TestNewIssueMsg(t *testing.T) {
 
 func TestIssueMsgType(t *testing.T) {
 	// Construct an IssueMsg
+	addr := sdk.Address([]byte("loan-from-bank"))
+	coins := sdk.Coins{{"atom", 10}}
 	var msg = IssueMsg{
-		Banker: sdk.Address([]byte("input")),
-		Outputs: []Output{
-			{
-				Address: sdk.Address([]byte("loan-from-bank")),
-				Coins:   sdk.Coins{{"atom", 10}},
-			},
-		},
+		Banker:  sdk.Address([]byte("input")),
+		Outputs: []Output{NewOutput(addr, coins)},
 	}
 
 	// TODO some failures for bad result
@@ -317,42 +276,34 @@ func TestIssueMsgValidation(t *testing.T) {
 
 func TestIssueMsgString(t *testing.T) {
 	// Construct a IssueMsg
+	addr := sdk.Address([]byte("loan-from-bank"))
+	coins := sdk.Coins{{"atom", 10}}
 	var msg = IssueMsg{
-		Banker: sdk.Address([]byte("input")),
-		Outputs: []Output{
-			{
-				Address: sdk.Address([]byte("loan-from-bank")),
-				Coins:   sdk.Coins{{"atom", 10}},
-			},
-		},
+		Banker:  sdk.Address([]byte("input")),
+		Outputs: []Output{NewOutput(addr, coins)},
 	}
 	res := msg.String()
+	// TODO: FIX THIS OUTPUT!
 	assert.Equal(t, res, "IssueMsg{696E707574#[Output{36433646363136453244363637323646364432443632363136453642,10atom}]}")
 }
 
 func TestIssueMsgGet(t *testing.T) {
+	addr := sdk.Address([]byte("loan-from-bank"))
+	coins := sdk.Coins{{"atom", 10}}
 	var msg = IssueMsg{
-		Banker: sdk.Address([]byte("input")),
-		Outputs: []Output{
-			{
-				Address: sdk.Address([]byte("loan-from-bank")),
-				Coins:   sdk.Coins{{"atom", 10}},
-			},
-		},
+		Banker:  sdk.Address([]byte("input")),
+		Outputs: []Output{NewOutput(addr, coins)},
 	}
 	res := msg.Get(nil)
 	assert.Nil(t, res)
 }
 
 func TestIssueMsgGetSignBytes(t *testing.T) {
+	addr := sdk.Address([]byte("loan-from-bank"))
+	coins := sdk.Coins{{"atom", 10}}
 	var msg = IssueMsg{
-		Banker: sdk.Address([]byte("input")),
-		Outputs: []Output{
-			{
-				Address: sdk.Address([]byte("loan-from-bank")),
-				Coins:   sdk.Coins{{"atom", 10}},
-			},
-		},
+		Banker:  sdk.Address([]byte("input")),
+		Outputs: []Output{NewOutput(addr, coins)},
 	}
 	res := msg.GetSignBytes()
 	// TODO bad results