diff --git a/src/main/java/minsecurity/identity/persist/sqlite/db/Db.java b/src/main/java/minsecurity/identity/persist/sqlite/db/Db.java
index 0043580..b39e543 100644
--- a/src/main/java/minsecurity/identity/persist/sqlite/db/Db.java
+++ b/src/main/java/minsecurity/identity/persist/sqlite/db/Db.java
@@ -15,11 +15,13 @@ import java.util.ArrayList;
 import java.util.Base64;
 import java.util.List;
 
+
 public final class Db {
     private static Identity getIdentityByNameFromStorage(String name, Connection c) throws Exception {
-        Statement stmt = c.createStatement();
-        ResultSet rs = stmt.executeQuery(String.format("SELECT * FROM identityinfo WHERE name = %s LIMIT 1", name)); // LIMIT 1代替Queryrow
-        stmt.close();
+        PreparedStatement pstmt = c.prepareStatement("SELECT * FROM identityinfo WHERE name = ? LIMIT 1");// LIMIT 1代替Queryrow
+        pstmt.setString(1, name);
+        ResultSet rs = pstmt.executeQuery();
+        pstmt.close();
         return getIdentityFromSqlRow(rs);
     }
 
@@ -86,7 +88,7 @@ public final class Db {
     }
 
     private static Identity getDefaultIdentityFromStorage(ResultSet rs) throws Exception{
-        if (rs == null)
+        if (!rs.isBeforeFirst())
             return null;
 
         String pubStr = "", priStr = "", pass = "", certStr = "", name = "", prikeyRawByte = "";
@@ -116,20 +118,18 @@ public final class Db {
     }
 
 
-    private static boolean setDefaultIdentityFromStorage(String name, Connection c) throws Exception{
+    private static void setDefaultIdentityFromStorage(String name, Connection c) throws Exception{
         PreparedStatement stmt = c.prepareStatement("update identityinfo set is_default = 1 where name= ?");
         stmt.setString(1, name);
         stmt.executeUpdate();
         stmt.close();
-        return true;
     }
 
-    private static boolean cancelDefaultIdentityFromStorage(String name, Connection c) throws Exception{
+    private static void cancelDefaultIdentityFromStorage(String name, Connection c) throws Exception{
         PreparedStatement stmt = c.prepareStatement("update identityinfo set is_default = 0 where name= ?");
         stmt.setString(1, name);
         stmt.executeUpdate();
         stmt.close();
-        return true;
     }
 
     public static List<Identity> getAllIdentityFromStorage(String name) throws Exception {
@@ -148,23 +148,105 @@ public final class Db {
         return getIdentityByNameFromStorage(name, c);
     }
 
-    private static boolean setDefaultIdentityByNameInStorage(String name) throws Exception {
+    private static void setDefaultIdentityByNameInStorage(String name) throws Exception {
         Connection c = Sqlite.getInstance().getConn();
-        return false;
+        c.setAutoCommit(false);
+        try{
+            PreparedStatement pstmt = c.prepareStatement("select * from identityinfo where name = ? LIMIT 1");
+            pstmt.setString(1, name);
+            ResultSet rs = pstmt.executeQuery(String.format("select * from identityinfo where name = %s LIMIT 1", name));
+            getDefaultIdentityFromStorage(rs);
+            pstmt.close();
+
+            PreparedStatement pstmt2 = c.prepareStatement("SELECT * from identityinfo where is_default = ?");
+            pstmt2.setInt(1, 1);
+            rs = pstmt2.executeQuery();
+            Identity id = getDefaultIdentityFromStorage(rs);
+            if (id != null){
+                cancelDefaultIdentityFromStorage(id.getName(), c);
+            }
+            setDefaultIdentityFromStorage(name, c);
+            pstmt2.close();
+            c.commit();
+            c.close();
+        }catch (Exception ex){
+            System.out.println(ex.getMessage());
+            c.rollback();
+            c.close();
+            throw ex;
+        }
     }
-    public static boolean SetDefaultIdentityByNameInStorage(String name) throws Exception {
+
+    public static void SetDefaultIdentityByNameInStorage(String name) throws Exception {
         for (int i = 0; i < 4; i++){
-            boolean res = false;
             try{
-                res = setDefaultIdentityByNameInStorage(name);
-                return res;
+                setDefaultIdentityByNameInStorage(name);
+                return;
             }catch (Exception ex){
+                if (i == 3)
+                    return;
                 if (ex.getMessage().equals("database is locked"))
                     Thread.sleep(50);
                 else
-                    return false;
+                    throw ex;
             }
         }
-        return false;
+    }
+
+    public static void deleteIdentityByName(String name) throws Exception{
+        Connection c = Sqlite.getInstance().getConn();
+        PreparedStatement pstmt = c.prepareStatement("elete from identityinfo where name=?");
+        pstmt.setString(1, name);
+        pstmt.executeUpdate();
+        pstmt.close();
+        c.close();
+    }
+
+    public static void persistIdentity(Identity identity) throws Exception{
+        Identity id = getIdentityByNameFromStorage(identity.getName());
+        if (id != null)
+            throw new Exception("The name has existed");
+
+        Connection c = Sqlite.getInstance().getConn();
+        String pubStr = "", priStr = "", certStr, prikeyRawByte = "";
+        int algo, sign;
+        if (identity.hasPrivateKey()){
+            byte[] priByte = identity.getPrikey().getBytes();
+            priStr = Base64.getEncoder().encodeToString(priByte);
+        }
+        if (identity.getPubkey() != null){
+            byte[] pubByte = identity.getPubkey().getBytes();
+            pubStr = Base64.getEncoder().encodeToString(pubByte);
+        }
+
+        algo = identity.getKeyParam().PublicKeyAlgorithm;
+        sign = identity.getKeyParam().SignatureAlgorithm;
+
+        certStr = CertUtils.toPem(identity.getCert(), null, Common.SM4ECB);
+
+        if (identity.getPrikeyRawByte() != null)
+            prikeyRawByte = Base64.getEncoder().encodeToString(identity.getPrikeyRawByte());
+
+        PreparedStatement pstmt = c.prepareStatement("INSERT INTO identityinfo(name, pubkey, prikey, pubkey_algo, signature_algo, pass, cert,prikey_raw_byte) values(?,?,?,?,?,?,?,?)");
+        pstmt.setString(1, identity.getName());
+        pstmt.setString(2, priStr);
+        pstmt.setString(3, pubStr);
+        pstmt.setInt(4, algo);
+        pstmt.setInt(5, sign);
+        pstmt.setString(6, identity.getPasswd());
+        pstmt.setString(7, certStr);
+        pstmt.setString(8, prikeyRawByte);
+
+        pstmt.executeUpdate();
+        pstmt.close();
+        c.close();
+    }
+
+    public Identity getDefaultIdentityFromStorage() throws Exception{
+        Connection c = Sqlite.getInstance().getConn();
+        PreparedStatement pstmt = c.prepareStatement("SELECT * from identityinfo where is_default= ? LIMIT 1");
+        pstmt.setInt(1, 1);
+        ResultSet rs = pstmt.executeQuery();
+        return getDefaultIdentityFromStorage(rs);
     }
 }