should work maybe?

examples/basecoin/app/app.go

@@ -70,6 +70,7 @@ func NewBasecoinApp(logger log.Logger, db dbm.DB) *BasecoinApp {
 
 	// register message routes
 	app.Router().
+		AddRoute("auth", auth.NewHandler(app.accountMapper.(auth.AccountMapper))).
 		AddRoute("bank", bank.NewHandler(app.coinKeeper)).
 		AddRoute("ibc", ibc.NewHandler(app.ibcMapper, app.coinKeeper)).
 		AddRoute("stake", stake.NewHandler(app.stakeKeeper))

examples/basecoin/app/app_test.go

@@ -208,6 +208,61 @@ func TestGenesis(t *testing.T) {
 	assert.Equal(t, acc, res1)
 }
 
+func TestMsgChangePubKey(t *testing.T) {
+
+	bapp := newBasecoinApp()
+
+	// Construct some genesis bytes to reflect basecoin/types/AppAccount
+	// Give 77 foocoin to the first key
+	coins, err := sdk.ParseCoins("77foocoin")
+	require.Nil(t, err)
+	baseAcc := auth.BaseAccount{
+		Address: addr1,
+		Coins:   coins,
+	}
+
+	// Construct genesis state
+	err = setGenesisAccounts(bapp, baseAcc)
+	assert.Nil(t, err)
+	// A checkTx context (true)
+	ctxCheck := bapp.BaseApp.NewContext(true, abci.Header{})
+	res1 := bapp.accountMapper.GetAccount(ctxCheck, addr1)
+	assert.Equal(t, baseAcc, res1.(*types.AppAccount).BaseAccount)
+
+	// Run a CheckDeliver
+	SignCheckDeliver(t, bapp, sendMsg1, []int64{0}, true, priv1)
+
+	// Check balances
+	CheckBalance(t, bapp, addr1, "67foocoin")
+	CheckBalance(t, bapp, addr2, "10foocoin")
+
+	changePubKeyMsg := auth.MsgChangeKey{
+		Address:   addr1,
+		NewPubKey: priv2.PubKey(),
+	}
+
+	ctxDeliver := bapp.BaseApp.NewContext(false, abci.Header{})
+	acc := bapp.accountMapper.GetAccount(ctxDeliver, addr1)
+
+	// send a MsgChangePubKey
+	SignCheckDeliver(t, bapp, changePubKeyMsg, []int64{1}, true, priv1)
+	acc = bapp.accountMapper.GetAccount(ctxDeliver, addr1)
+
+	assert.True(t, priv2.PubKey().Equals(acc.GetPubKey()))
+
+	// signing a SendMsg with the old privKey should be an auth error
+	tx := genTx(sendMsg1, []int64{2}, priv1)
+	res := bapp.Deliver(tx)
+	assert.Equal(t, sdk.ToABCICode(sdk.CodespaceRoot, sdk.CodeUnauthorized), res.Code, res.Log)
+
+	// resigning the tx with the new correct priv key should work
+	SignCheckDeliver(t, bapp, sendMsg1, []int64{2}, true, priv2)
+
+	// Check balances
+	CheckBalance(t, bapp, addr1, "57foocoin")
+	CheckBalance(t, bapp, addr2, "20foocoin")
+}
+
 func TestMsgSendWithAccounts(t *testing.T) {
 	bapp := newBasecoinApp()