In my world an advanced alien civilization are worshiped as gods by the human population. As the gods have better things to do than actually spend time interacting with the local fauna they created a hybrid through genetic engineering, combining traits of both their own species and humanity to create something closer to humans in thoughts and feelings to interact through. Humanity perceive these hybrids as demigods much akin to classic Greek heroes like Herakles and the like.
The alien technology is treated like magic, and can only be utilized by the demigods*. The reason for this is that the alien tech is more or less programmed to only respond to beings with the gods' genetic code.
The demigods must place their God-Hand, their right hand that is designed to be similar to their divine progenitors, on the device to activate it.
My question is are there any good reasons why they may need to utilize their god-hand specifically? My understanding of genetics would lead me to think no part of their body is technically more or less "alien" than another, even if the body exhibits more traits from the alien side than the human.
Further Information: These hybrids are the product of very advanced genetic engineering and were specifically designed the way they were. I do not know if this makes the god-hand more or less likely to make sense.
Note*: I had intended for humans to be able to utilize the god-tech by using the blood of demigods to fool the devices into letting them access the controls.
More Information: The humans are pre-industrial on a planet with very little easily accessible precious metals, forcing them to exist in a pseudo-stone age level of technology.