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Glossary

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A

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Access Policy

A set of rules defining who can access content, when, and how many times. Stored on the Base blockchain.

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AES-GCM

Advanced Encryption Standard - Galois/Counter Mode. A symmetric encryption algorithm providing confidentiality and authentication.

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Attempt

One instance of a recipient trying to access content. Tracked on-chain via logAttempt().

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B

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Base

An Ethereum Layer 2 blockchain by Coinbase. SHIELD deploys its smart contracts on Base.

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Blockchain

A distributed, immutable ledger. SHIELD uses Base for transparent, trustless access control.

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C

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CID (Content Identifier)

A unique hash identifying content on IPFS. SHIELD encrypted content is referenced by CID.

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Contract

A smart contract on the blockchain. SHIELD’s Shield.sol contract manages access policies.

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D

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dApp (Decentralized Application)

An application with backend running on blockchain. SHIELD is a dApp.

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Decryption

Converting encrypted content back to plaintext. Happens client-side in SHIELD.

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E

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EIP-4361

Ethereum Improvement Proposal for Sign-In with Ethereum (SIWE). SHIELD uses this for authentication.

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Encryption

Converting plaintext to ciphertext. SHIELD uses AES-GCM 256 client-side.

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End-to-End Encryption

Encryption where only sender and recipient can decrypt. SHIELD implements this.

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F

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Faucet

A service providing free test ETH. Use Alchemy Faucet for Base Sepolia.

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G

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Gas

Fee paid to execute transactions on blockchain. Paid in ETH on Base.

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Gateway

A server providing HTTP access to IPFS content. SHIELD uses Pinata’s gateway.

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H

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Hash

A fixed-size output from a cryptographic function. Used for policy IDs and CIDs.

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Hardhat

Ethereum development environment. Used for SHIELD contract development.

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I

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IPFS (InterPlanetary File System)

Decentralized file storage. SHIELD stores encrypted content on IPFS via Pinata.

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IV (Initialization Vector)

A random value ensuring same plaintext encrypts differently each time. 96 bits in AES-GCM.

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J

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JWT (JSON Web Token)

A token format for session management. SHIELD uses JWT for API sessions.

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K

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Key

A secret value for encryption/decryption. In SHIELD, keys are 256-bit random values.

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L

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Link (Secure Link)

A URL containing policyId and secretKey. Created once, shown once, never recoverable.

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M

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Mainnet

The production blockchain network. Base mainnet is where real value is at stake.

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Max Attempts

Maximum times content can be accessed. Set by sender.

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Metadata

Information about content (size, type) but not the content itself. Stored off-chain.

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N

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Next.js

React framework. Powers SHIELD frontend.

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Nonce

A number used once. Prevents replay attacks in SIWE.

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P

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Pinata

IPFS pinning service. SHIELD uses Pinata to persist encrypted content.

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Policy ID

Unique identifier for an access policy. Keccak256 hash stored on-chain.

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R

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Recipient

The wallet address authorized to access content. Set when creating a policy.

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Revoke

Invalidate a policy before expiration. Irreversible.

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S

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Secret Key

The decryption key. Embedded in URL fragment, never sent to server.

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Sender

The creator of a secure link. Pays gas for policy creation.

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Sepolia

Testnet for Base. Used for development and testing.

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SIWE (Sign-In with Ethereum)

Authentication standard using Ethereum signatures. Replaces passwords.

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Smart Contract

Program running on blockchain. SHIELD’s Shield.sol enforces access rules.

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T

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Tailwind CSS

Utility-first CSS framework. Styles SHIELD UI.

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Testnet

Test blockchain network. No real value, used for testing.

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Transaction

Data submitted to blockchain. Costs gas. SHIELD has createPolicy and logAttempt transactions.

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Trustless

System requiring no trusted parties. SHIELD’s architecture is trustless.

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U

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URL Fragment

Part of URL after #. SHIELD puts secret keys here—never sent to server.

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V

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Vercel

Hosting platform. SHIELD frontend deploys to Vercel.

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View Function

Smart contract function that reads state without transaction. isPolicyValid is a view function.

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W

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Wallet

Software for managing private keys. MetaMask, Rainbow, etc.

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WalletConnect

Protocol for connecting wallets to dApps. SHIELD uses WalletConnect.

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Web Crypto API

Browser API for cryptography. SHIELD uses it for AES-GCM.

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Web3

Decentralized web ecosystem. SHIELD is a web3 application.

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Z

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Zero Address

0x000...000. Invalid address. Cannot be used as recipient.