diff --git a/kt/client.go b/kt/client.go
index bbb3101..06311f1 100644
--- a/kt/client.go
+++ b/kt/client.go
@@ -29,7 +29,7 @@ type clientErr struct {
 
 // checkDig checks for freshness and prior vals, and evid / err on fail.
 func (c *Client) checkDig(dig *SigDig) *clientErr {
-	stdErr := &clientErr{evid: nil, err: true}
+	stdErr := &clientErr{err: true}
 	// check sig.
 	err0 := CheckSigDig(dig, c.servSigPk)
 	if err0 {
@@ -42,7 +42,7 @@ func (c *Client) checkDig(dig *SigDig) *clientErr {
 			evid := &Evid{sigDig0: dig, sigDig1: seenDig}
 			return &clientErr{evid: evid, err: true}
 		} else {
-			return &clientErr{evid: nil, err: false}
+			return &clientErr{err: false}
 		}
 	}
 	// check for freshness.
@@ -55,7 +55,7 @@ func (c *Client) checkDig(dig *SigDig) *clientErr {
 	}
 	c.seenDigs[dig.Epoch] = dig
 	c.nextEpoch = dig.Epoch + 1
-	return &clientErr{evid: nil, err: false}
+	return &clientErr{err: false}
 }
 
 // checkVrfProof errors on fail.
@@ -105,7 +105,7 @@ func (c *Client) checkNonMemb(uid uint64, ver uint64, dig []byte, nonMemb *NonMe
 
 // Put rets the epoch at which the key was put, and evid / error on fail.
 func (c *Client) Put(pk []byte) (uint64, *clientErr) {
-	stdErr := &clientErr{evid: nil, err: true}
+	stdErr := &clientErr{err: true}
 	dig, latest, bound, err0 := callServPut(c.servCli, c.uid, pk)
 	if err0 {
 		return 0, stdErr
@@ -129,7 +129,7 @@ func (c *Client) Put(pk []byte) (uint64, *clientErr) {
 		return 0, stdErr
 	}
 	c.nextVer += 1
-	return dig.Epoch, &clientErr{evid: nil, err: false}
+	return dig.Epoch, &clientErr{err: false}
 }
 
 // Get returns if the pk was registered, the pk, and the epoch
@@ -138,7 +138,7 @@ func (c *Client) Put(pk []byte) (uint64, *clientErr) {
 // e.g., if don't track vers properly, bound could be off.
 // e.g., if don't check isReg alignment with hist, could have fraud non-exis key.
 func (c *Client) Get(uid uint64) (bool, []byte, uint64, *clientErr) {
-	stdErr := &clientErr{evid: nil, err: true}
+	stdErr := &clientErr{err: true}
 	dig, hist, isReg, latest, bound, err0 := callServGet(c.servCli, uid)
 	if err0 {
 		return false, nil, 0, stdErr
@@ -168,13 +168,13 @@ func (c *Client) Get(uid uint64) (bool, []byte, uint64, *clientErr) {
 	if c.checkNonMemb(uid, boundVer, dig.Dig, bound) {
 		return false, nil, 0, stdErr
 	}
-	return isReg, latest.CommOpen.Pk, dig.Epoch, &clientErr{evid: nil, err: false}
+	return isReg, latest.CommOpen.Pk, dig.Epoch, &clientErr{err: false}
 }
 
 // SelfMon self-monitors for the client's own key, and returns the epoch
 // through which it succeeds, or evid / error on fail.
 func (c *Client) SelfMon() (uint64, *clientErr) {
-	stdErr := &clientErr{evid: nil, err: true}
+	stdErr := &clientErr{err: true}
 	dig, bound, err0 := callServSelfMon(c.servCli, c.uid)
 	if err0 {
 		return 0, stdErr
@@ -186,13 +186,13 @@ func (c *Client) SelfMon() (uint64, *clientErr) {
 	if c.checkNonMemb(c.uid, c.nextVer, dig.Dig, bound) {
 		return 0, stdErr
 	}
-	return dig.Epoch, &clientErr{evid: nil, err: false}
+	return dig.Epoch, &clientErr{err: false}
 }
 
 // auditEpoch checks a single epoch against an auditor, and evid / error on fail.
 // pre-cond: we've seen this epoch.
 func (c *Client) auditEpoch(epoch uint64, adtrCli *advrpc.Client, adtrPk cryptoffi.PublicKey) *clientErr {
-	stdErr := &clientErr{evid: nil, err: true}
+	stdErr := &clientErr{err: true}
 	adtrInfo, err0 := callAdtrGet(adtrCli, epoch)
 	if err0 {
 		return stdErr
@@ -215,13 +215,13 @@ func (c *Client) auditEpoch(epoch uint64, adtrCli *advrpc.Client, adtrPk cryptof
 		evid := &Evid{sigDig0: servDig, sigDig1: seenDig}
 		return &clientErr{evid: evid, err: true}
 	}
-	return &clientErr{evid: nil, err: false}
+	return &clientErr{err: false}
 }
 
 func (c *Client) Audit(adtrAddr uint64, adtrPk cryptoffi.PublicKey) *clientErr {
 	adtrCli := advrpc.Dial(adtrAddr)
 	// check all epochs that we've seen before.
-	var err0 = &clientErr{evid: nil, err: false}
+	var err0 = &clientErr{err: false}
 	for ep := range c.seenDigs {
 		err1 := c.auditEpoch(ep, adtrCli, adtrPk)
 		if err1.err {
diff --git a/merkle/merkle.go b/merkle/merkle.go
index f2eb1c0..a6764ea 100644
--- a/merkle/merkle.go
+++ b/merkle/merkle.go
@@ -81,7 +81,7 @@ func (n *node) updateInteriorHash() {
 // It'll be specialized after adding it to the tree.
 func newGenericNode() *node {
 	c := make([]*node, numChildren)
-	return &node{val: nil, hash: nil, children: c}
+	return &node{children: c}
 }
 
 type Digest = []byte
@@ -296,7 +296,7 @@ func (t *Tree) Get(id Id) *GetReply {
 	digest := std.BytesClone(nodePath[0].getHash())
 	proof := getChildHashes(nodePath, id)
 	if lastNode == nil {
-		return &GetReply{Val: nil, Digest: digest, ProofTy: NonmembProofTy,
+		return &GetReply{Digest: digest, ProofTy: NonmembProofTy,
 			Proof: proof, Error: errNone}
 	} else {
 		val := std.BytesClone(lastNode.val)