diff --git a/service/censusmanager.go b/service/censusmanager.go
index 4bb6da1..aad9dc5 100644
--- a/service/censusmanager.go
+++ b/service/censusmanager.go
@@ -6,13 +6,13 @@ import (
 	"log"
 	"net/http"
 	"strconv"
-	"strings"
 	"time"
 
 	tree "github.com/vocdoni/dvote-census/tree"
 	signature "github.com/vocdoni/dvote-relay/crypto/signature"
 )
 
+const hashSize = 32
 const authTimeWindow = 10         // Time window (seconds) in which TimeStamp will be accepted if auth enabled
 var MkTrees map[string]*tree.Tree // MerkleTree dvote-census library
 var Signatures map[string]string
@@ -20,6 +20,7 @@ var Signature signature.SignKeys // Signature dvote-relay library
 
 type Claim struct {
 	CensusID  string `json:"censusID"`  // References to MerkleTree namespace
+	RootHash  string `json:"rootHash"`  // References to MerkleTree rootHash
 	ClaimData string `json:"claimData"` // Data to add to the MerkleTree
 	ProofData string `json:"proofData"` // MerkleProof to check
 	TimeStamp string `json:"timeStamp"` // Unix TimeStamp in seconds
@@ -98,8 +99,9 @@ func claimHandler(w http.ResponseWriter, req *http.Request, op string) {
 	}
 
 	// Process data
-	log.Printf("Received censusID:{%s} claimData:{%s} proofData:{%s} timeStamp:{%s} signature:{%s}\n",
-		c.CensusID, c.ClaimData, c.ProofData, c.TimeStamp, c.Signature)
+	log.Printf("censusID:{%s} rootHash:{%s} claimData:{%s} proofData:{%s} timeStamp:{%s} signature:{%s}\n",
+		c.CensusID, c.RootHash, c.ClaimData, c.ProofData, c.TimeStamp, c.Signature)
+	authString := fmt.Sprintf("%s%s%s%s", c.CensusID, c.RootHash, c.ClaimData, c.TimeStamp)
 	resp.Error = false
 	resp.Response = ""
 	censusFound := false
@@ -114,14 +116,8 @@ func claimHandler(w http.ResponseWriter, req *http.Request, op string) {
 	}
 
 	if op == "add" {
-		msg := fmt.Sprintf("%s%s%s", c.CensusID, c.ClaimData, c.TimeStamp)
-		if auth := checkAuth(c.TimeStamp, c.Signature, Signatures[c.CensusID], msg); auth {
-			if strings.HasPrefix(c.CensusID, "0x") {
-				resp.Error = true
-				resp.Response = "add claim to snapshot is not allowed"
-			} else {
-				err = MkTrees[c.CensusID].AddClaim([]byte(c.ClaimData))
-			}
+		if auth := checkAuth(c.TimeStamp, c.Signature, Signatures[c.CensusID], authString); auth {
+			err = MkTrees[c.CensusID].AddClaim([]byte(c.ClaimData))
 		} else {
 			resp.Error = true
 			resp.Response = "invalid authentication"
@@ -129,61 +125,107 @@ func claimHandler(w http.ResponseWriter, req *http.Request, op string) {
 	}
 
 	if op == "gen" {
-		resp.Response, err = MkTrees[c.CensusID].GenProof([]byte(c.ClaimData))
+		var t *tree.Tree
+		var err error
+		if len(c.RootHash) > 1 { //if rootHash specified
+			t, err = MkTrees[c.CensusID].Snapshot(c.RootHash)
+			if err != nil {
+				log.Printf("Snapshot error: %s", err.Error())
+				resp.Error = true
+				resp.Response = "invalid root hash"
+				reply(&resp, w)
+				return
+			}
+		} else { //if rootHash not specified use current tree
+			t = MkTrees[c.CensusID]
+		}
+		resp.Response, err = t.GenProof([]byte(c.ClaimData))
+		if err != nil {
+			resp.Error = true
+			resp.Response = err.Error()
+			reply(&resp, w)
+			return
+		}
 	}
 
 	if op == "root" {
 		resp.Response = MkTrees[c.CensusID].GetRoot()
 	}
 
+	if op == "idx" {
+
+	}
+
 	if op == "dump" {
-		values, err := MkTrees[c.CensusID].Dump()
+		var t *tree.Tree
+		if auth := checkAuth(c.TimeStamp, c.Signature, Signatures[c.CensusID], authString); !auth {
+			resp.Error = true
+			resp.Response = "invalid authentication"
+			reply(&resp, w)
+			return
+		}
+
+		if len(c.RootHash) > 1 { //if rootHash specified
+			t, err = MkTrees[c.CensusID].Snapshot(c.RootHash)
+			if err != nil {
+				log.Printf("Snapshot error: %s", err.Error())
+				resp.Error = true
+				resp.Response = "invalid root hash"
+				reply(&resp, w)
+				return
+			}
+		} else { //if rootHash not specified use current merkletree
+			t = MkTrees[c.CensusID]
+		}
+
+		//dump the claim data and return it
+		values, err := t.Dump()
 		if err != nil {
 			resp.Error = true
-			resp.Response = fmt.Sprint(err)
+			resp.Response = err.Error()
 		} else {
 			jValues, err := json.Marshal(values)
 			if err != nil {
 				resp.Error = true
-				resp.Response = fmt.Sprint(err)
+				resp.Response = err.Error()
 			} else {
 				resp.Response = string(jValues)
 			}
 		}
 	}
 
-	if op == "snapshot" {
-		msg := fmt.Sprintf("%s%s%s", c.CensusID, c.ClaimData, c.TimeStamp)
-		if auth := checkAuth(c.TimeStamp, c.Signature, Signatures[c.CensusID], msg); auth {
-			if strings.HasPrefix(c.CensusID, "0x") {
+	if op == "check" {
+		if len(c.ProofData) < 1 {
+			resp.Error = true
+			resp.Response = "proofData not provided"
+			reply(&resp, w)
+			return
+		}
+		var t *tree.Tree
+		if len(c.RootHash) > 1 { //if rootHash specified
+			t, err = MkTrees[c.CensusID].Snapshot(c.RootHash)
+			if err != nil {
+				log.Printf("Snapshot error: %s", err.Error())
 				resp.Error = true
-				resp.Response = "snapshot an snapshot makes no sense"
-			} else {
-				snapshotNamespace, err := MkTrees[c.CensusID].Snapshot()
-				if err != nil {
-					resp.Error = true
-					resp.Response = fmt.Sprint(err)
-				} else {
-					resp.Response = snapshotNamespace
-				}
+				resp.Response = "invalid root hash"
+				reply(&resp, w)
+				return
 			}
-		} else {
-			resp.Error = true
-			resp.Response = "invalid authentication"
+		} else { //if rootHash not specified use current merkletree
+			t = MkTrees[c.CensusID]
 		}
-	}
 
-	if op == "check" {
-		if len(c.ProofData) < 1 {
+		validProof, err := t.CheckProof([]byte(c.ClaimData), c.ProofData)
+		if err != nil {
 			resp.Error = true
-			resp.Response = "proofData not provided"
+			resp.Response = err.Error()
+			reply(&resp, w)
+			return
+		}
+		if validProof {
+			resp.Response = "valid"
 		} else {
-			validProof, _ := MkTrees[c.CensusID].CheckProof([]byte(c.ClaimData), c.ProofData)
-			if validProof {
-				resp.Response = "valid"
-			} else {
-				resp.Response = "invalid"
-			}
+			resp.Response = "invalid"
 		}
 	}
 
@@ -211,9 +253,6 @@ func Listen(port int, proto string) {
 	http.HandleFunc("/getRoot", func(w http.ResponseWriter, r *http.Request) {
 		claimHandler(w, r, "root")
 	})
-	http.HandleFunc("/snapshot", func(w http.ResponseWriter, r *http.Request) {
-		claimHandler(w, r, "snapshot")
-	})
 	http.HandleFunc("/dump", func(w http.ResponseWriter, r *http.Request) {
 		claimHandler(w, r, "dump")
 	})
diff --git a/tree/tree.go b/tree/tree.go
index 4ebeac6..d3bf3e3 100644
--- a/tree/tree.go
+++ b/tree/tree.go
@@ -1,8 +1,8 @@
 package tree
 
 import (
+	"bytes"
 	"errors"
-	"fmt"
 	"os/user"
 
 	common3 "github.com/iden3/go-iden3/common"
@@ -103,6 +103,16 @@ func (t *Tree) GetRoot() string {
 	return t.Tree.RootKey().String()
 }
 
+func (t *Tree) GetIndex(data []byte) (string, error) {
+	e, err := t.GetClaim(data)
+	if err != nil {
+		return "", err
+	}
+	index, err := t.Tree.GetDataByIndex(e.Entry().HIndex())
+	return index.String(), err
+}
+
+/*
 func (t *Tree) Dump() ([]string, error) {
 	var response []string
 
@@ -121,8 +131,20 @@ func (t *Tree) Dump() ([]string, error) {
 	})
 	return response, err
 }
+*/
+
+func (t *Tree) Dump() (string, error) {
+	w := bytes.NewBufferString("")
+	err := t.Tree.DumpClaims(w, nil) // as rootKey we can pass a nil pointer, and it will use the current RootKey
+
+	return w.String(), err
+}
 
-func (t *Tree) Snapshot() (string, error) {
-	snapshotNamespace := t.Tree.RootKey().String()
-	return snapshotNamespace, nil
+func (t *Tree) Snapshot(root string) (*Tree, error) {
+	var rootHash merkletree.Hash
+	copy(rootHash[:32], root)
+	mt, err := t.Tree.Snapshot(&rootHash)
+	snapshotTree := new(Tree)
+	snapshotTree.Tree = mt
+	return snapshotTree, err
 }