Using a keygen (software that generates fake serial numbers) is illegal software piracy . CorelDRAW X6 was released in 2012 and is now abandonware (no longer sold or supported by Corel). However, using a keygen still carries risks: viruses, trojans, Windows registry corruption, and legal liability if used commercially.
If you absolutely need old CorelDRAW for legacy files, run a (VM) without internet access and test the keygen there – but still not recommended.