diff --git a/node/node.go b/node/node.go
index 539e315dc..0a11074e5 100644
--- a/node/node.go
+++ b/node/node.go
@@ -41,7 +41,15 @@ type Node struct {
 	privKey          crypto.PrivKeyEd25519
 }
 
-func NewNode() *Node {
+func NewNodeDefaultPrivVal() *Node {
+	// Get PrivValidator
+	privValidatorFile := config.GetString("priv_validator_file")
+	privValidator := types.LoadOrGenPrivValidator(privValidatorFile)
+
+	return NewNode(privValidator)
+}
+
+func NewNode(privValidator *types.PrivValidator) *Node {
 	// Get BlockStore
 	blockStoreDB := dbm.GetDB("blockstore")
 	blockStore := bc.NewBlockStore(blockStoreDB)
@@ -58,10 +66,6 @@ func NewNode() *Node {
 	// add the chainid to the global config
 	config.Set("chain_id", state.ChainID)
 
-	// Get PrivValidator
-	privValidatorFile := config.GetString("priv_validator_file")
-	privValidator := types.LoadOrGenPrivValidator(privValidatorFile)
-
 	// Generate node PrivKey
 	privKey := crypto.GenPrivKeyEd25519()
 
@@ -249,6 +253,9 @@ func makeNodeInfo(sw *p2p.Switch, privKey crypto.PrivKeyEd25519) *p2p.NodeInfo {
 
 //------------------------------------------------------------------------------
 
+// Users wishing to use an external signer for their validators
+// should fork tendermint/tendermint and implement RunNode to
+// load their custom priv validator and call NewNode(privVal)
 func RunNode() {
 
 	// Wait until the genesis doc becomes available
@@ -274,7 +281,7 @@ func RunNode() {
 	}
 
 	// Create & start node
-	n := NewNode()
+	n := NewNodeDefaultPrivVal()
 	l := p2p.NewDefaultListener("tcp", config.GetString("node_laddr"), config.GetBool("skip_upnp"))
 	n.AddListener(l)
 	err := n.Start()
diff --git a/node/node_test.go b/node/node_test.go
index 49e7d3ddf..c6a9c1c26 100644
--- a/node/node_test.go
+++ b/node/node_test.go
@@ -24,7 +24,7 @@ func TestNodeStartStop(t *testing.T) {
 	time.Sleep(time.Second * 2)
 
 	// Create & start node
-	n := NewNode()
+	n := NewNodeDefaultPrivVal()
 	l := p2p.NewDefaultListener("tcp", config.GetString("node_laddr"), config.GetBool("skip_upnp"))
 	n.AddListener(l)
 	n.Start()
diff --git a/types/priv_validator.go b/types/priv_validator.go
index e2536e47d..4ad1de3e1 100644
--- a/types/priv_validator.go
+++ b/types/priv_validator.go
@@ -35,12 +35,15 @@ func voteToStep(vote *Vote) int8 {
 }
 
 type PrivValidator struct {
-	Address    []byte                `json:"address"`
-	PubKey     crypto.PubKeyEd25519  `json:"pub_key"`
-	PrivKey    crypto.PrivKeyEd25519 `json:"priv_key"`
-	LastHeight int                   `json:"last_height"`
-	LastRound  int                   `json:"last_round"`
-	LastStep   int8                  `json:"last_step"`
+	Address    []byte               `json:"address"`
+	PubKey     crypto.PubKeyEd25519 `json:"pub_key"`
+	LastHeight int                  `json:"last_height"`
+	LastRound  int                  `json:"last_round"`
+	LastStep   int8                 `json:"last_step"`
+
+	// PrivKey should be empty if a Signer other than the default is being used.
+	PrivKey crypto.PrivKeyEd25519 `json:"priv_key"`
+	signer  Signer
 
 	// For persistence.
 	// Overloaded for testing.
@@ -48,6 +51,32 @@ type PrivValidator struct {
 	mtx      sync.Mutex
 }
 
+// XXX: This is used to sign votes.
+// It is the caller's duty to verify the msg before calling Sign,
+// eg. to avoid double signing.
+// Currently, the only callers are SignVote and SignProposal
+type Signer interface {
+	Sign(msg []byte) crypto.SignatureEd25519
+}
+
+// Implements Signer
+type DefaultSigner struct {
+	priv crypto.PrivKeyEd25519
+}
+
+func NewDefaultSigner(priv crypto.PrivKeyEd25519) *DefaultSigner {
+	return &DefaultSigner{priv: priv}
+}
+
+// Implements Signer
+func (ds *DefaultSigner) Sign(msg []byte) crypto.SignatureEd25519 {
+	return ds.priv.Sign(msg).(crypto.SignatureEd25519)
+}
+
+func (privVal *PrivValidator) SetSigner(s Signer) {
+	privVal.signer = s
+}
+
 // Generates a new validator with private key.
 func GenPrivValidator() *PrivValidator {
 	privKeyBytes := new([64]byte)
@@ -63,6 +92,7 @@ func GenPrivValidator() *PrivValidator {
 		LastRound:  0,
 		LastStep:   stepNone,
 		filePath:   "",
+		signer:     NewDefaultSigner(privKey),
 	}
 }
 
@@ -76,6 +106,7 @@ func LoadPrivValidator(filePath string) *PrivValidator {
 		Exit(Fmt("Error reading PrivValidator from %v: %v\n", filePath, err))
 	}
 	privVal.filePath = filePath
+	privVal.signer = NewDefaultSigner(privVal.PrivKey)
 	return privVal
 }
 
@@ -145,14 +176,10 @@ func (privVal *PrivValidator) SignVote(chainID string, vote *Vote) error {
 	privVal.save()
 
 	// Sign
-	privVal.SignVoteUnsafe(chainID, vote)
+	vote.Signature = privVal.signer.Sign(SignBytes(chainID, vote))
 	return nil
 }
 
-func (privVal *PrivValidator) SignVoteUnsafe(chainID string, vote *Vote) {
-	vote.Signature = privVal.PrivKey.Sign(SignBytes(chainID, vote)).(crypto.SignatureEd25519)
-}
-
 func (privVal *PrivValidator) SignProposal(chainID string, proposal *Proposal) error {
 	privVal.mtx.Lock()
 	defer privVal.mtx.Unlock()
@@ -167,7 +194,7 @@ func (privVal *PrivValidator) SignProposal(chainID string, proposal *Proposal) e
 		privVal.save()
 
 		// Sign
-		proposal.Signature = privVal.PrivKey.Sign(SignBytes(chainID, proposal)).(crypto.SignatureEd25519)
+		proposal.Signature = privVal.signer.Sign(SignBytes(chainID, proposal))
 		return nil
 	} else {
 		return errors.New(fmt.Sprintf("Attempt of duplicate signing of proposal: Height %v, Round %v", proposal.Height, proposal.Round))
diff --git a/types/vote_set_test.go b/types/vote_set_test.go
index 92686c91e..629a54e94 100644
--- a/types/vote_set_test.go
+++ b/types/vote_set_test.go
@@ -60,7 +60,7 @@ func withBlockPartsHeader(vote *Vote, blockPartsHeader PartSetHeader) *Vote {
 }
 
 func signAddVote(privVal *PrivValidator, vote *Vote, voteSet *VoteSet) (bool, error) {
-	privVal.SignVoteUnsafe(config.GetString("chain_id"), vote)
+	vote.Signature = privVal.signer.Sign(SignBytes(config.GetString("chain_id"), vote))
 	added, _, err := voteSet.AddByAddress(privVal.Address, vote)
 	return added, err
 }