You have to pick:

Such a decryption algorithm would completely destroy the internet. You couldn't protect anything. As soon as some idiot wants to wreck something, it is wrecked.

By what means?
Magic? Me? Random guys?
As long as it's not the middle one, I'm fine with this.

I'm thinking its magic but you would show up as the father in the paternity test.

Is this like an aura of pregnancy or a one time thing?

Permanent aura

One the other hand having no encryption would allow anyone easy access to everything, even if the programmers didn't make any mistakes. Having no encryption, I think, would help those who are already powerful. The reason being that the easiest way to attack something becomes the man-in-the-middle. Just intercept packets and you know everything two computers are sending each other. And who can best do man-in-the-middle attacks? People who run the middle - internet service providers and telecommunications companies.

If it's by magic, then would they still get pregnant if they physically can't?

awkward when you visit your family

It occurs to me that this doesn't limit the effect to *human* females.

Those paternity tests could potentially become extremely embarrassing. And many interesting hybrids would ensue.

I think (and hope) it means human females.