I assume you mean that you are using a child theme based on Twenty Twelve. That being the case, you would just include the appropriate file or files in your child theme.

Your child theme could include a single.php file edited to do what you want, but you probably don’t have to. That file calls get_template_part( 'content', get_post_format() ); to display the content, which will load one of these:

• comments.php
• content-aside.php
• content-image.php
• content-link.php
• content-none.php
• content-page.php
• content-quote.php
• content-status.php
• content.php

Your child theme can include one or more of those files edited to be missing the author data.

Nothing gets removed from the parent. The files just get substituted.

Reference:

http://codex.wordpress.org/Child_Themes