### System Overview The goal is to create a platform where citizens can anonymously submit opinions on legislative matters, with those opinions influencing lawmakers, while guaranteeing transparency and security. Zero-Knowledge Proofs, a cryptographic tool, enable participants to prove eligibility and uniqueness without revealing their identities. The system integrates digital credentials, blind signatures, and ZKPs, optionally leveraging a blockchain for decentralization and auditability. --- ### Key Features 1. **Anonymity**: Participants’ identities remain hidden, even from the system and authorities. 2. **Eligibility**: Only authorized individuals (e.g., citizens) can participate. 3. **Uniqueness**: Each participant submits only one opinion per legislative matter. 4. **Transparency**: All submissions and proofs are publicly verifiable. 5. **Security**: Cryptographic methods prevent fraud, manipulation, or duplicate submissions. --- ### System Components - **Participants**: Individuals with a digital credential (e.g., issued by a trusted authority based on citizenship). - **Trusted Authority**: Issues credentials and blind signatures to ensure eligibility. - **Public Ledger (Optional Blockchain)**: Stores commitments, submissions, and proofs for transparency and verification. - **Legislative Matters**: Each matter (e.g., a proposed law) has a unique identifier, called a “matter ID.” --- ### How the System Works The system operates in two main phases: **Setup** and **Opinion Submission**. #### 1. Setup Phase For each legislative matter identified by a unique matter ID: - **Credential Issuance**: Each participant has a digital credential from a trusted authority, proving eligibility (e.g., citizenship). This credential is private and tied to their identity initially but anonymized in later steps. - **Token and Commitment Generation**: - For each matter, the participant generates: - A **unique token** (a random value specific to that matter). - A **secret key** (a private value known only to them). - They create a **commitment**—a cryptographic hash of the token and secret key combined with the matter ID. This commitment hides the token and key but can later be proven to match them. - **Blind Signature Request**: - The participant sends the commitment and matter ID to the authority, with the token portion blinded (using a blind signature scheme like Chaum’s blind signatures). - The authority verifies that this credential hasn’t requested a signature for this matter ID before, then issues a **partially blind signature**. The signature includes the matter ID (visible to the authority) and the blinded commitment. - The participant unblinds the signature, obtaining a valid signature on their commitment tied to the matter ID. - **Publishing Commitments**: - The participant publishes the commitment and its blind signature to a public ledger (e.g., a blockchain or database). - The authority ensures each credential gets only one signature per matter, limiting each participant to one commitment per matter. At the end of the setup phase, there’s a public list of commitments for each matter, each with a valid blind signature, ensuring only eligible participants contribute exactly one commitment. #### 2. Opinion Submission Phase When a participant wants to submit an opinion on a legislative matter: - **Submission Content**: - The participant reveals their **token** for that matter. - They provide their **opinion** (e.g., “yes,” “no,” or a short statement). - They generate a **Zero-Knowledge Proof (ZKP)** that proves: 1. There exists a commitment in the public list for this matter ID where the revealed token matches the committed token. 2. They know the secret key associated with that commitment. - **Verification**: - The system (or a smart contract on a blockchain) verifies: - The commitment referenced by the ZKP has a valid blind signature from the authority. - The ZKP is correct, confirming the token’s legitimacy and the participant’s knowledge of the secret key. - The token hasn’t been used before for this matter (checked against a list of used tokens). - **Recording**: - If valid, the system accepts the opinion, records it publicly with the token and ZKP, and marks the token as used. --- ### Ensuring Core Requirements - **Anonymity**: - Blind signatures ensure the authority doesn’t link commitments to participants. - The ZKP hides which commitment corresponds to the submission, mixing it among all participants’ commitments. - Tokens are unique per matter and unlinkable across matters, preventing profiling. - **Eligibility**: - Only participants with a valid credential can obtain blind signatures and publish commitments. - **Uniqueness**: - The authority issues one blind signature per credential per matter, limiting each participant to one commitment. - The ZKP and token check ensure each commitment submits only one opinion per matter. - **Transparency**: - All commitments, signatures, opinions, tokens, and ZKPs are public. Anyone can verify that submissions correspond to valid commitments and that no token is reused. - **Security**: - ZKPs require knowledge of the secret key, preventing token theft. - Blind signatures and commitments prevent the authority or outsiders from manipulating the process. - A blockchain (if used) ensures tamper-proof records. --- ### Optional Blockchain Integration For enhanced transparency and decentralization: - **Commitments**: Stored as transactions on the blockchain during setup. - **Submissions**: Each opinion submission is a transaction, verified by a smart contract that checks the ZKP and token uniqueness. - **Auditability**: The blockchain provides a tamper-proof log, allowing anyone to audit the process without trusting a central entity. This reduces reliance on a single authority, though the authority still issues initial credentials and signatures. A fully decentralized identity system could further minimize this dependency. --- ### Scalability and Efficiency - **Large Populations**: For millions of participants, the system manages large lists of commitments and used tokens. Modern databases or blockchains (e.g., Ethereum with rollups) can handle this scale. - **Efficient ZKPs**: Using zk-SNARKs or zk-STARKs, proofs are small (e.g., a few hundred bytes) and verification is fast (e.g., milliseconds), making the system practical. - **Setup Overhead**: Participants generate commitments per matter, which could be streamlined with reusable credentials, but the current design prioritizes security and simplicity. --- ### Example Workflow 1. **Setup for Matter “Law123”**: - Alice, with credential C1, generates token T1 and secret key S1, commits to them as Com1 = Hash(T1, S1, “Law123”). - She gets a blind signature Sig1 from the authority on Com1 for “Law123” and publishes (Com1, Sig1). 2. **Submission**: - Alice submits her opinion “Yes” on “Law123” with: - Token T1. - ZKP proving T1 matches a commitment (e.g., Com1) and she knows S1. - The system verifies Sig1, the ZKP, and that T1 is unused, then records “Yes” with T1. 3. **Public Check**: - Anyone sees (Com1, Sig1) in the list, verifies Sig1, and confirms T1’s submission is valid and unique. --- ### Conclusion This system leverages ZKPs, blind signatures, and a public ledger to crowdsource public opinion securely and transparently. It ensures anonymity and fairness while allowing lawmakers to trust the authenticity of the input, making it a robust tool for democratic participation in legislation.