Replay Protection

Mechanisms like chain IDs, EIP‑155 signing domains, and unique nonces that prevent transactions from being valid across different networks or contexts.

Replay Attack

Attack where a valid transaction is captured and resent on the same or another chain to repeat effects, mitigated by chain IDs, nonces, and domain separation.

Relay Chain

In multi‑chain designs like Polkadot, the central chain that coordinates consensus and communication among connected parachains.

ReFi, Regenerative Finance

Movement using web3 rails to fund public goods and ecological projects with transparent on‑chain incentives and impact tracking.

Reentrancy

Smart contract vulnerability where an external call re‑enters the calling contract before state updates finalize, enabling double‑spend style exploits without proper guards.

Rebase Token

Token that programmatically expands or contracts user balances to target a price or supply, keeping proportional ownership the same.

RPC, Remote Procedure Call

Endpoint that lets applications read chain data and send transactions to nodes, usually via JSON‑RPC over HTTP or WebSockets.

Retrieval Index

Data structure that accelerates similarity search, for example HNSW graphs or IVF lists over embedding vectors.

Retrieval (AI)

Selecting the most relevant documents, chunks, or vectors from a corpus given a user query, typically via embeddings and similarity search.

Red Teaming (AI)

Systematic probing of an AI model with adversarial inputs to discover safety, security, and alignment weaknesses before release.

Reward Model

Model trained to score outputs according to preferences or policies, used to guide reinforcement learning or re‑ranking of generations.

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