diff --git a/src/anonymizer.ts b/src/anonymizer.ts
index 88bf9d8..e82fe80 100644
--- a/src/anonymizer.ts
+++ b/src/anonymizer.ts
@@ -18,33 +18,27 @@ export class Anonymizer {
     reuse an Anonymizer.
     
   */
+ 
   private patientID: string;
-  
-  private id_prefix: string | undefined;
-  private id_suffix: string | undefined;
-  private seed: string | undefined;
-
-  
+  private date_offset_hours: number  
   randomizer: Randomizer;
   address_anonymizer: AddressAnonymizer;
   element_handlers: any[];
-  private date_offset_hours: number
   
-  constructor( patientID: string, id_prefix?: string | undefined, id_suffix?: string | undefined, seed?: string | undefined) {
+  
+  constructor( patientID: string, protected_tags?: string[], id_prefix?: string, id_suffix?: string, seed?: string) {
     const minimum_offset_hours: number = 62 * 24;
     const maximum_offset_hours: number = 730 * 24;
     this.patientID = patientID;
-    this.id_prefix = id_prefix;
-    this.id_suffix = id_suffix;
-    this.seed = seed;
-    this.randomizer = new Randomizer(this.seed)
+    this.randomizer = new Randomizer(seed)
     this.date_offset_hours = Number(-(
       this.randomizer.toInt("date_offset") % (BigInt(maximum_offset_hours) - BigInt(minimum_offset_hours)) + BigInt(minimum_offset_hours)
     ))
     //this.data = data;
     this.address_anonymizer = new AddressAnonymizer(this.randomizer);
     this.element_handlers = 
-        [new UnwantedElementStripper(["00101081",//"BranchOfService",
+        [new Protector(protected_tags).protect,
+         new UnwantedElementStripper(["00101081",//"BranchOfService",
                                       "00102180",//"Occupation",
                                       "00101090",//"MedicalRecordLocator",
                                       "00101080",//"MilitaryRank",
@@ -73,7 +67,7 @@ export class Anonymizer {
                                       "00081010",//"StationName",
                                       "00200010",//"StudyID"
                                       ], 
-                                      undefined, undefined).anonymize,                              
+                                      id_prefix, id_suffix).anonymize,                              
         this.address_anonymizer.anonymize,
         new InstitutionAnonymizer(this.address_anonymizer).anonymize,
         new FixedValueAnonymizer("00100020", this.patientID).anonymize,
diff --git a/src/datetimeanonymizer.ts b/src/datetimeanonymizer.ts
index 5d19281..30277e6 100644
--- a/src/datetimeanonymizer.ts
+++ b/src/datetimeanonymizer.ts
@@ -116,7 +116,7 @@ export class DateTimeAnonymizer{
     
     
 
-    zipLongest = (fillValue: any | undefined, ...arr: any[]): string[][] =>{
+    zipLongest = (fillValue: string = "", ...arr: any[]): string[][] =>{
         const maxLength = Math.max(...arr.map((arr: any) => arr.length));
     
         return Array.from({ length: maxLength }, (_, index) => {
diff --git a/src/idanonymizer.ts b/src/idanonymizer.ts
index 8c7847a..68cd0c9 100644
--- a/src/idanonymizer.ts
+++ b/src/idanonymizer.ts
@@ -6,15 +6,15 @@ export class IDAnonymizer {
   
     private keywords: string[];
     private randomizer: Randomizer;
-    private id_suffix: string | undefined;
-    private id_prefix: string | undefined;
+    private id_suffix: string;
+    private id_prefix: string;
     private issuer_tag: string;
     //private tag_ids: string[];
     private alphabet: string;
     private totalAffixesLength: number;
     private indicesForRandomizer: number[];
 
-    constructor(Randomizer: Randomizer, keywords: string[],  id_prefix?: string | undefined, id_suffix?: string | undefined) {
+    constructor(Randomizer: Randomizer, keywords: string[],  id_prefix: string = "", id_suffix: string = "") {
         this.keywords = keywords;
         this.randomizer = Randomizer;
         this.id_prefix = id_prefix;
@@ -22,21 +22,7 @@ export class IDAnonymizer {
         this.issuer_tag = dcmjs.data.DicomMetaDictionary.nameMap["IssuerOfPatientID"].tag
         //this.tag_ids =  this.keywords.map(tag_name => dcmjs.data.DicomMetaDictionary.unpunctuateTag(dcmjs.data.DicomMetaDictionary.nameMap[tag_name].tag));
         this.alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
-
-        if (this.id_prefix && this.id_suffix){
-            this.totalAffixesLength = this.id_prefix.length + this.id_suffix.length
-        } else if (this.id_prefix && !this.id_suffix){
-            this.id_suffix = ""
-            this.totalAffixesLength = this.id_prefix.length
-
-        } else if (!this.id_prefix && this.id_suffix){
-            this.id_prefix = ""
-            this.totalAffixesLength = this.id_suffix.length
-        }
-        else {
-            this.totalAffixesLength = 0
-        }
-        
+        this.totalAffixesLength = this.id_prefix.length + this.id_suffix.length
         this.indicesForRandomizer = new Array<number>(12 - this.totalAffixesLength).fill(this.alphabet.length)
     }
 
diff --git a/src/pnanonymizer.ts b/src/pnanonymizer.ts
index 8a234d3..11db94c 100644
--- a/src/pnanonymizer.ts
+++ b/src/pnanonymizer.ts
@@ -32,7 +32,7 @@ export class PNAnonymizer {
     return true
   }
 
-  new_pn(original_value: string, sex?: string | undefined,){
+  new_pn(original_value: string, sex: string = "",){
     let first_names: string[];
     if (sex == "F"){
       first_names = this.lists.female_first_names;}
diff --git a/src/randomizer.ts b/src/randomizer.ts
index ea6204c..ce8a1a4 100644
--- a/src/randomizer.ts
+++ b/src/randomizer.ts
@@ -4,8 +4,8 @@ import getRandomValues from 'get-random-values'; // use only in node env
 export class Randomizer {
   private seed: string;
 
-  constructor(seed?: string | undefined ) {
-    if (seed != null || seed === undefined) {
+  constructor(seed: string = "" ) {
+    if (seed == "") {
       this.seed = this.generateRandomSeed();
     } else {
       this.seed = seed;
@@ -67,8 +67,6 @@ export class Randomizer {
     for (const x of suprema) {
       const s = BigInt(x)
       result.push(Number(big_Int % s));
-      // console.log(s, big_Int, big_Int%s);
-      // console.log(BigInt(Math.floor(Number(big_Int / s))));
       big_Int = big_Int / s;
     }