mcrypt deprecated in php7.2

I've installed ASTPP on a system with php 7.2.
I get a blank page after installation.
In astpp/index.php I uncommented the line with 'ini_set('display_errors','on');' and changed the ENVIRONMENT to 'development'

I get the following errors when I call the URL:

<h4>A PHP Error was encountered</h4>

<p>Severity: 8192</p>
<p>Message: Function mcrypt_get_iv_size() is deprecated</p>
<p>Filename: libraries/Encrypt.php</p>
<p>Line Number: 323</p>

</div><div style="border:1px solid #990000;padding-left:20px;margin:0 0 10px 0;">

<h4>A PHP Error was encountered</h4>

<p>Severity: 8192</p>
<p>Message: Function mcrypt_create_iv() is deprecated</p>
<p>Filename: libraries/Encrypt.php</p>
<p>Line Number: 324</p>

</div><div style="border:1px solid #990000;padding-left:20px;margin:0 0 10px 0;">

<h4>A PHP Error was encountered</h4>

<p>Severity: 8192</p>
<p>Message: Function mcrypt_encrypt() is deprecated</p>
<p>Filename: libraries/Encrypt.php</p>
<p>Line Number: 325</p>

</div><br />

<b>Fatal error</b>: Cannot declare class Locale, because the name is already in use in <b>/var/www/html/astpp/application/libraries/locale.php</b> on line <b>29</b><br />

mcrypt has been deprecated from php 7.2. The mcrypt code will have to be replaced.