diff --git a/kt/client.go b/kt/client.go
index e7e5b82..7381eed 100644
--- a/kt/client.go
+++ b/kt/client.go
@@ -59,15 +59,15 @@ func (c *Client) checkDig(dig *SigDig) *clientErr {
 
 // checkVrfProof errors on fail.
 // TODO: if VRF pubkey is bad, does VRF.Verify still mean something?
-func (c *Client) checkVrf(uid uint64, ver uint64, label []byte, proof []byte) bool {
+func checkVrf(pk *cryptoffi.VrfPublicKey, uid uint64, ver uint64, label []byte, proof []byte) bool {
 	pre := &MapLabelPre{Uid: uid, Ver: ver}
 	preByt := MapLabelPreEncode(make([]byte, 0), pre)
-	return !c.servVrfPk.Verify(preByt, label, proof)
+	return !pk.Verify(preByt, label, proof)
 }
 
 // checkMemb errors on fail.
-func (c *Client) checkMemb(uid uint64, ver uint64, dig []byte, memb *Memb) bool {
-	if c.checkVrf(uid, ver, memb.Label, memb.VrfProof) {
+func checkMemb(pk *cryptoffi.VrfPublicKey, uid uint64, ver uint64, dig []byte, memb *Memb) bool {
+	if checkVrf(pk, uid, ver, memb.Label, memb.VrfProof) {
 		return true
 	}
 	mapVal := compMapVal(memb.EpochAdded, memb.CommOpen)
@@ -75,19 +75,19 @@ func (c *Client) checkMemb(uid uint64, ver uint64, dig []byte, memb *Memb) bool
 }
 
 // checkMembHide errors on fail.
-func (c *Client) checkMembHide(uid uint64, ver uint64, dig []byte, memb *MembHide) bool {
-	if c.checkVrf(uid, ver, memb.Label, memb.VrfProof) {
+func checkMembHide(pk *cryptoffi.VrfPublicKey, uid uint64, ver uint64, dig []byte, memb *MembHide) bool {
+	if checkVrf(pk, uid, ver, memb.Label, memb.VrfProof) {
 		return true
 	}
 	return merkle.CheckProof(true, memb.MerkProof, memb.Label, memb.MapVal, dig)
 }
 
 // checkHist errors on fail.
-func (c *Client) checkHist(uid uint64, dig []byte, membs []*MembHide) bool {
+func checkHist(pk *cryptoffi.VrfPublicKey, uid uint64, dig []byte, membs []*MembHide) bool {
 	var err0 bool
 	for ver0, memb := range membs {
 		ver := uint64(ver0)
-		if c.checkMembHide(uid, ver, dig, memb) {
+		if checkMembHide(pk, uid, ver, dig, memb) {
 			err0 = true
 		}
 	}
@@ -95,8 +95,8 @@ func (c *Client) checkHist(uid uint64, dig []byte, membs []*MembHide) bool {
 }
 
 // checkNonMemb errors on fail.
-func (c *Client) checkNonMemb(uid uint64, ver uint64, dig []byte, nonMemb *NonMemb) bool {
-	if c.checkVrf(uid, ver, nonMemb.Label, nonMemb.VrfProof) {
+func checkNonMemb(pk *cryptoffi.VrfPublicKey, uid uint64, ver uint64, dig []byte, nonMemb *NonMemb) bool {
+	if checkVrf(pk, uid, ver, nonMemb.Label, nonMemb.VrfProof) {
 		return true
 	}
 	return merkle.CheckProof(false, nonMemb.MerkProof, nonMemb.Label, nil, dig)
@@ -114,7 +114,7 @@ func (c *Client) Put(pk []byte) (uint64, *clientErr) {
 		return 0, err1
 	}
 	// check latest entry has right ver, epoch, pk.
-	if c.checkMemb(c.uid, c.nextVer, dig.Dig, latest) {
+	if checkMemb(c.servVrfPk, c.uid, c.nextVer, dig.Dig, latest) {
 		return 0, stdErr
 	}
 	if dig.Epoch != latest.EpochAdded {
@@ -124,7 +124,7 @@ func (c *Client) Put(pk []byte) (uint64, *clientErr) {
 		return 0, stdErr
 	}
 	// check bound has right ver.
-	if c.checkNonMemb(c.uid, c.nextVer+1, dig.Dig, bound) {
+	if checkNonMemb(c.servVrfPk, c.uid, c.nextVer+1, dig.Dig, bound) {
 		return 0, stdErr
 	}
 	c.nextVer += 1
@@ -146,7 +146,7 @@ func (c *Client) Get(uid uint64) (bool, []byte, uint64, *clientErr) {
 	if err1.err {
 		return false, nil, 0, err1
 	}
-	if c.checkHist(uid, dig.Dig, hist) {
+	if checkHist(c.servVrfPk, uid, dig.Dig, hist) {
 		return false, nil, 0, stdErr
 	}
 	numHistVers := uint64(len(hist))
@@ -155,7 +155,7 @@ func (c *Client) Get(uid uint64) (bool, []byte, uint64, *clientErr) {
 		return false, nil, 0, stdErr
 	}
 	// check latest has right ver.
-	if isReg && c.checkMemb(uid, numHistVers, dig.Dig, latest) {
+	if isReg && checkMemb(c.servVrfPk, uid, numHistVers, dig.Dig, latest) {
 		return false, nil, 0, stdErr
 	}
 	// check bound has right ver.
@@ -164,7 +164,7 @@ func (c *Client) Get(uid uint64) (bool, []byte, uint64, *clientErr) {
 	if isReg {
 		boundVer = numHistVers + 1
 	}
-	if c.checkNonMemb(uid, boundVer, dig.Dig, bound) {
+	if checkNonMemb(c.servVrfPk, uid, boundVer, dig.Dig, bound) {
 		return false, nil, 0, stdErr
 	}
 	return isReg, latest.CommOpen.Pk, dig.Epoch, &clientErr{err: false}
@@ -182,7 +182,7 @@ func (c *Client) SelfMon() (uint64, *clientErr) {
 	if err1.err {
 		return 0, err1
 	}
-	if c.checkNonMemb(c.uid, c.nextVer, dig.Dig, bound) {
+	if checkNonMemb(c.servVrfPk, c.uid, c.nextVer, dig.Dig, bound) {
 		return 0, stdErr
 	}
 	return dig.Epoch, &clientErr{err: false}