I need an alogorithm to get same value after encryption if i use same string.
<apex:page controller="encryptNewController">
    <apex:form >  
         <apex:outPutLabel value="Encrypted by Code"/>
         <apex:inputsecret value="{!encryptedByCode}"/>
       
       
         <apex:commandButton value="Save" action="{!saveValues}"/>
         <apex:outputText value="{!decryptedDataString}"/>
    </apex:form>
</apex:page>


public with sharing class encryptNewController {

     Public Encrypt_Object__c encryptObject {get;set;}
     Public String encryptedByCode {get;set;}
     Public String decryptedDataString {get;set;}
     Blob cryptoKey;
     public encryptNewController(){
          encryptObject=new Encrypt_Object__c();
     }
     public void saveValues(){
            List<CryptoKey__c> keyValue = [SELECT  Key__c FROM CryptoKey__c where id != null];
                String cryptoKeyString;
                System.debug('000000000000000000000000000000000000000000keyValue'+keyValue);
                if(keyValue.size() > 0){
                    cryptoKeyString = keyValue[0].Key__c;
                    cryptoKey = EncodingUtil.base64Decode(cryptoKeyString);
                System.debug('000000000000000000000000000000000000000000cryptoKey'+cryptoKey);
            }          
            encryptObject.Encrypted_by_Code__c = encryptToken(encryptedByCode);
          
            insert encryptObject;
            Encrypt_Object__c insertedencryptObject = [Select id,Encrypted_by_Code__c from Encrypt_Object__c where id=: encryptObject.id][0];
            decryptedDataString =decryptToken(insertedencryptObject.Encrypted_by_Code__c);           
     }
 
     public String encryptToken(String strOriginal){
        Blob encryptedData;
        if(cryptoKey != null){
            String strUrlUTF8 = EncodingUtil.urlEncode(strOriginal, 'UTF-8');
            Blob b = Blob.valueOf(strUrlUTF8);
            System.debug('@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@cryptoKey'+cryptoKey);
            encryptedData = Crypto.encryptWithManagedIV('AES256', cryptoKey, b);
            return  EncodingUtil.base64Encode(encryptedData);
        }else{
            return null;
        }
      
      }
   
      public String decryptToken(String encryptedString){
        if(cryptoKey != null){
         Blob b = EncodingUtil.base64Decode(encryptedString);
         Blob decryptedData = Crypto.decryptWithManagedIV('AES256', cryptoKey, b);
         String strUrlUTF8 = decryptedData.toString();
         return EncodingUtil.urlDecode(strUrlUTF8, 'UTF-8');
        }else{
            return null;
        }
      }  
}
================================================
This is my page and class to encrypt the string entered and save on databease.
Each time the 'Key__c' is same as i take from custom settings.
But when i enter 'abc' and save two times the entered value is different.
What is the reason?
Isn't  same string encrypt with same key generate same encrypted value?
Thanks in advance