The imaginary friends test

The imaginary friends test is a technique to evaluate attack resistance of trust metrics and online systems in general, in particular Sybil attacks. It was proposed by Robin Upton and available as a Powerpoint presentation at altruists.org in the context of a course on Altruistic Economics.

Introduction to Imaginary Friends
Altruistic Economics is a decentralized system, so users have a lot of autonomy such as ... the chance to create Imaginary Friends. Rewarding such Imaginary Friends would encourage deception. Imaginary Friend is an alternate term for sybil attack, fake identity, puppet identity.

The Imaginary Friends Test
The Imaginary Friends Test allows to answer to the question "Does it help to create ‘imaginary friends’?".

It the test is passed (the answer is "no"), then there is no incentive to cheat by creating fake identities and this happens when fake identities make no difference or are a disadvantage.

It it is not passed (the answer is "yes"), then there is incentive to cheat by creating fake identities and this happens when fake identities are an advantage.