Glossary

This glossary defines the terms used across Z’s documentation. Additional terms will join the glossary as their pages ship. Anonymity set. The set of users among whom a specific shielded transaction is indistinguishable. The larger the anonymity set, the stronger the privacy. Association set proof. A zero-knowledge proof that a user’s deposit is included in a defined “good” subset of the ShieldedPool, without revealing which deposit. Attestation. Cryptographic evidence that a piece of code is running inside a genuine, untampered hardware enclave. Tiers 3 and 4 of the gateway require valid attestation before any payload is dispatched. AUP attestation. A wallet-signed attestation that the principal accepts Z’s Acceptable Use Policy. Required for every Tier 4 session and re-signed when the AUP version is updated. Blake2b. A hash function used by Z. Accessed via Solidity libraries today; will be exposed as a precompile when Z Chain ships. BN254. The elliptic curve used by the ShieldedPool’s Groth16 proof system. Broadcaster. An off-chain agent that submits ShieldedPool RelayAdapter transactions on behalf of users. Paid through fees inside the shielded transaction. Replaces what other systems call a “relayer.” Commitment. A cryptographic hash representing a shielded note. Commitments are anchored in the ShieldedPool’s global Merkle tree. Groth16. The zero-knowledge proof system used by the ShieldedPool. Chosen for excellent proving and verification performance on the BN254 curve. Guardrail. A safety mechanism applied to a request. Includes content scanning (CSAM check on Tiers 2 and 3), tier-enforcement gates, and policy filters. MPP. Machine Payments Protocol. A session payment mechanism using Stripe PaymentIntents in deposit mode to pre-authorize a balance that subsequent inference requests draw down. Settled in USDC via Stripe’s Agentic Commerce Suite at phase one. Nullifier. A deterministic value derived from a shielded note’s secret data. Spending a note publishes the nullifier; the same nullifier cannot be republished, preventing double-spending. Paymaster. An ERC-4337 component that pays gas on behalf of a user, enabling gasless UX. Poseidon. A ZK-friendly hash function used for commitment generation in the ShieldedPool. Chosen for low gas cost inside a proof. RelayAdapter. A contract pattern that lets an application interact with shielded users without knowing who they are. Unshields input from the ShieldedPool, executes the application call, reshields output back into the pool, all atomically. Shell. ERC-4337 wallet account contract used by Z to support agent-native settlement, gasless transactions, and account-abstracted authentication. ShieldedPool. Z’s multi-asset privacy primitive. Deposited assets become private notes; balances, transfers, and asset types inside the pool are cryptographically hidden. Deployed on the host EVM chain. SIWE / SIWS. Sign-In With Ethereum / Sign-In With Solana. Wallet-native authentication protocols where a wallet signs a structured message to prove control of an address. Stealth address. An address derived deterministically from a user’s keys that appears unrelated to the user’s primary address. Used for receiving shielded payments without linkability. TEE. Trusted Execution Environment. Hardware enclaves that produce attestations of their code and configuration. Underlies Tiers 3 and 4 of the gateway. Trust tier. One of four cryptographically enforced trust postures for an inference request: Tier 1 (Anonymous), Tier 2 (Private), Tier 3 (TEE), Tier 4 (E2EE). Unlinkable. A property of a shielded transaction or position: an outside observer cannot connect the transaction or position back to the user’s identity or to other transactions by the same user. Viewing key. A read-only key for a ShieldedPool account. Shared with a recipient (an accountant, a regulator, an auditor) gives them scoped access to transaction history without spending authority. x402. A protocol for in-band payment over HTTP. A 402 Payment Required response carries payment requirements; the client constructs a payment proof and retries. Z. The protocol. Used in running text where context makes the reference unambiguous; “Z Protocol” where formal naming is preferred. Z Compute. Z’s broader verifiable-compute substrate. The inference node layer is the first instance; Z Compute as a general developer surface is on the roadmap. Z Inference. The inference layer of Z. The Z Inference Gateway is the primary surface. z.infer(). The contract-callable interface for dispatching inference from Solidity. Available on the host EVM chain. Z Lend. Private lending market. Z Protocol. Formal name of the protocol. Often shortened to “Z” in running text. Z Trade. Private trading venue. Zcosystem. The utility surface built on Z. ZDR. Zero Data Retention. Z’s policy and architectural commitment that prompts and completions are not retained. On Tier 4, ZDR is architecturally enforced. The gateway holds no decryption key. On Tiers 1 through 3, ZDR is a policy commitment supported by architecturally constrained logging. ZP. The internal accounting unit for credits. One ZP equals one cent. ZSP. Zcash Satoshi Plus. Z Chain’s consensus mechanism. Not live; ships with Z Chain.