Using Secure Hardware to Harden Casper for Greater Defense In Depth

Background

What is SGX?

  • Executing one’s applications on an untrusted machine with guaranteed confidentiality and integrity of output.
  • Users to run the desired software in an untampered environment in a remote machine.

Proof of Stake Protocols and Casper

  1. Among the online participants, the majority of the stake is controlled by honest or rational participants.
  2. The network is highly synchronous, i.e. recipients receive messages within a known, short, bounded delay.
  3. It is not possible to reverse the chain from a block which is too far in the history (ie., more than X blocks behind the latest block) (in SnowWhite), or users must know who are the latest participants in the protocol (Casper) in order to determine which chain is the correct one. This assumption solves the long-range fork attack in which an attacker, after cashing out, forks the chain at some previous block to create a new valid-looking chain.
  4. There exists some mechanism to incentivize users to participate in the protocol, otherwise no protocol is secure against an attacker who controls even 10% of the coin if only 15% of the stakes are used in the protocol. This assumption builds atop assumption (1). If we can incentivize users to join the protocol, condition (1) is easily satisfied.

Hardening against long-range forks

Running Ethereum full nodes in SGX enclaves which can provide the latest validator set to users in the network
  • Intel Corporation didn’t backdoor SGX.
  • The hardware protecting the enclave.

Lowering the barrier to validator participation

A naive delegation protocol in Casper which allows users with less than the Casper minimum stake, i.e. 1000 ETH in this example, to indirectly participate in the Casper protocol.
Running the code of the delegate nodes inside SGX protect users from malicious delegator

Hardening time-synchrony

Hardening initial peer-joining

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KyberNetwork, SmartPool

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Loi Luu

Loi Luu

KyberNetwork, SmartPool

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