Proof of Elapsed Time (PoET)

PoET's fairness relies on a hardware-based Trusted Execution Environment (TEE), like Intel SGX, to generate cryptographically verifiable random wait times. This ensures the timer process is tamper-proof and cannot be manipulated by the node operator, preventing a single node from consistently winning the leader election.

Unlike Proof of Work (PoW), PoET does not require nodes to solve computationally intensive puzzles. Instead, they sleep for their assigned duration. This makes it a highly energy-efficient consensus model, with power consumption comparable to standard server operations, enabling more sustainable blockchain networks.

The core process where each validator requests a random wait time from its TEE. The network participant whose timer expires first becomes the block leader for that round. This process is repeated for each new block, ensuring decentralized and probabilistic block production.

The TEE produces a signed attestation or certificate that proves the node genuinely waited for the full duration. Other nodes can instantly verify this proof without re-executing the wait, allowing for fast block validation and maintaining high network throughput.

PoET is primarily designed for permissioned blockchain networks (e.g., Hyperledger Sawtooth). It assumes a known set of vetted participants, as the security model depends on the integrity of the licensed TEE hardware, making it less suitable for permissionless, anonymous environments.

The mechanism aims for fair access to block production, as each node has an equal statistical chance of winning an election round. Sybil attacks are mitigated because creating multiple identities does not increase winning odds, as each identity requires its own certified TEE.

The Trusted Execution Environment (TEE), such as Intel SGX, is the root of trust for PoET. It is a secure, isolated area of a processor that ensures code executes with integrity and confidentiality. The TEE generates a cryptographically signed wait timer, proving a node waited the required duration without the possibility of software-level manipulation.

PoET's security is inherently centralized around the hardware vendor (e.g., Intel). This creates critical risks:

• Single Point of Failure: A vulnerability in the TEE design compromises the entire network.
• Vendor Lock-in: The network depends on a specific manufacturer's hardware and continued support.
• Supply Chain Attacks: Malicious hardware or compromised manufacturing could undermine the trust model.

The core security operation is the verifiable random wait. Each node requests a timer from its local TEE. The node with the shortest timer becomes the leader. Other nodes verify the winning timer's cryptographic attestation, which proves it was generated correctly by a genuine TEE and that the wait time has expired. This prevents nodes from forging shorter wait times.

PoET resists Sybil attacks (where one entity creates many fake identities) by tying identity to physical hardware. Each legitimate TEE provides a unique attestation. While an attacker could amass many TEE-enabled machines, the capital cost of hardware acts as a sybil resistance mechanism, making it economically impractical to dominate leader election through identity creation alone.

PoET is designed as an energy-efficient alternative to Proof of Work (PoW).

• Energy Use: PoET uses minimal energy vs. PoW's massive computational expenditure.
• Security Basis: PoW security comes from economic cost (burned energy). PoET security comes from hardware trust (TEE integrity).
• Decentralization: PoW is permissionless at the hardware level; PoET is permissioned by the TEE vendor's ecosystem.

The original blockchain consensus mechanism, used by Bitcoin. It requires nodes (miners) to solve computationally intensive cryptographic puzzles to propose a new block. This process, called hashing, consumes significant energy but provides robust security through economic disincentives for malicious behavior. PoET was created as a direct, energy-efficient alternative to PoW.

A consensus mechanism where validators are chosen to propose and attest to blocks based on the amount of cryptocurrency they "stake" as collateral. It replaces energy-intensive computation with economic stake. While both PoET and PoS are energy-efficient, PoS relies on explicit capital lock-up, whereas PoET uses a randomized wait time based on trusted hardware.

A property of a distributed system that can reach consensus even if some components (nodes) fail or act maliciously (are "Byzantine"). Many modern consensus protocols, including those used in conjunction with PoET (like Sawtooth's PBFT), incorporate BFT principles to ensure network safety and liveness despite faulty participants.

The fundamental process in many consensus algorithms to select which node has the right to propose the next block. PoET solves leader election via a fair lottery system: each node waits a random amount of time, and the first to finish its wait becomes the leader. This contrasts with PoW (leader = first to solve puzzle) and PoS (leader = chosen by stake-based algorithm).