Hi Guys
I am able to encrypt some value ,But I dont know while I am doinf decrypt some error is showing
System.StringException: Unrecognized base64 character: %
Error is in expression '{!test}' in component <apex:commandButton> in page encryptpageformac

I am sharing my page and controller , Help me guys as soon as possible

My page
<apex:page standardController="EnCrypt_Decrypt__c" extensions="EncryptExtensionForMAC">
    <apex:form >
        <apex:pageBlock >
            <apex:pageBlockSection >
                <apex:inputField value="{!encrypt.Name}"/>
                <apex:commandButton value="Save" action="{!Save}"/>
                <apex:commandButton value="Update" action="{!test}"/>
            </apex:pageBlockSection>
        </apex:pageBlock>
    </apex:form>
</apex:page>

My controller
public class EncryptExtensionForMAC {
    public EnCrypt_Decrypt__c encrypt{get;set;}
    public String secretkey = 'INVOICEITAPIACERTISCLOUDSEP2010';
    Blob cryptoKey = Blob.valueOf(secretkey );
    String algorithmName = 'HMACSHA256';
    public Id recordId{get;set;}
    public EncryptExtensionForMAC(ApexPages.StandardController controller) {
      
        //cryptoKey = Crypto.generateAesKey(256);
        recordId = Apexpages.CurrentPage().getParameters().get('id');
        if(recordId !=null){
            encrypt = [SELECT id,Name From EnCrypt_Decrypt__c
                    WHERE id=:recordId];
        }
        else{
            encrypt = new EnCrypt_Decrypt__c();
        }
    }
  
    public PageReference Save(){
       
       
         Blob input = Blob.valueOf(encrypt.Name);
         Blob signing =Crypto.generateMac(algorithmName, input, cryptoKey);
         //String macUrl = EncodingUtil.urlEncode(EncodingUtil.base64Encode(signing), 'UTF-16');
        String macUrl = EncodingUtil.base64Encode(signing);
         encrypt.name = macUrl;
       
         insert encrypt;
         return null;
    }
  
     public PageReference test(){
         Blob input = EncodingUtil.base64Decode(encrypt.Name);
      
         Blob signing =Crypto.generateMac(algorithmName, input, cryptoKey);
         String macUrl = signing.toString();
         encrypt.name = macUrl ;
       
         update encrypt;
         return null;
    }

}
Error is showing when I am clicking on the Update button.