Shared resources can cut the real cost of Sybil identities
Original title: Identity Amortization: Shared Resources and the Cost of Sybil Attacks
Published phone-verification prices overstate per-account cost 1.6 to 4.3 times; a Tor relay-limit change cut modeled attack cost 8 to 72%.
The paper defines identity amortization as a lower minimum cost of provisioning identities when one resource can support several of them. Defenses that assign influence per identity and price each one separately can overestimate a Sybil threshold by up to the number of identities one resource supports. Exact tests that use only prices and capacities show when amortization starts and its largest error; a sharing cap below onset removes it.
Unconfirmed: Cost ratios are modeled from published prices, not measured in live Sybil attacks.
- On published phone-verification prices, per-account estimates overstate cost 1.6 to 4.3 times.
- Tor's higher per-address relay limit cut modeled attack cost by 8 to 72%.
- That Tor range depends on the address-to-relay price ratio.
- A sharing cap below the onset of amortization removes the gap.
From the original article
1 min read at arxiv.orgSybil defenses commonly price identities by requiring a resource for each one. When one resource can support several identities, an adversary can pay less per identity than the defense intends. We call this identity amortization: a strict reduction in the minimum cost of provisioning identities when resources may be shared, relative to provisioning each one independently.
By Homayoun Maleki · arxiv.org
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