Member id encrypt decrypt issue

Hi All Members,

My requirement is, how we will encrypt {member_id} in template file without using any plugins.

Actually I have form with hidden values and I have tried with using php code in template file for encrypt member id.

<?php
 $supplier_id = ee()->encrypt->encode('{member_id}');
?>
<input type="hidden" name="supplier_id" id="supplier_id" value="<?php echo $supplier_id; ?>" />

But when we submit the form it goes to action modules function and it’s return the same value like {member_id} and code is below

$supplier_id = ee()->input->post('supplier_id', TRUE);
$supplier_id_decrypt = ee()->encrypt->decode($supplier_id); 

echo $supplier_id_decrypt;  //{member_id}

Please check and advise