Organisation withholding service certificate and relieving letter

I sent an email containing a programming script out of my office email to my personal mail ID for learning purpose. However, it was assumed that this code might be circulated to other competitors which may harm company's business and reputation. Considering this, company has put this as InfoSec Policy violation and issued me Show cause notice to provide valid justification for my actions. which I provided within 24 hours as learning reasons. However, today was asked to sign an undertaking that the company will ne holding my FnF settlement of dues, service certificate & Reliving letter (I'm already on my Notice period with last date being 17th Aug.) till the time this is amicably settled between the customer I was working for & my Org. Moreover I'm also asked to keep my org indemnified & hold harmless for the above action. I didn't sign the undertaking as this sounded fishy to me as I already provided my justification in a show cause notice. What implications can they impose on me now?