ZkpSharp 1.4.0

ZkpSharp

A .NET library for Zero-Knowledge Proofs with Stellar Soroban blockchain integration. Prove facts about private data (age, balance, membership, range, time conditions) without revealing the data itself.

Features

Privacy proofs (HMAC-based commitment schemes) -- fast, lightweight:

• Proof of Age, Balance, Membership, Range, Time Condition
• HMAC-SHA256 with cryptographic salt

True zero-knowledge proofs (Bulletproofs) -- mathematically sound:

• ZK range, age, and balance proofs using Pedersen commitments
• Compact serialization for storage and transmission

Stellar blockchain integration:

• Soroban SDK 25 with BLS12-381 cryptography
• On-chain verification via InvokeHostFunctionOp
• SorobanTransactionBuilder for XDR construction

Installation

dotnet add package ZkpSharp

Quick start

using ZkpSharp.Core;
using ZkpSharp.Security;

var proofProvider = new ProofProvider("your-base64-encoded-32-byte-key");
var zkp = new Zkp(proofProvider);

// Prove age >= 18 without revealing birthdate
var (proof, salt) = zkp.ProveAge(new DateTime(1995, 3, 15));
bool valid = zkp.VerifyAge(proof, new DateTime(1995, 3, 15), salt);

// Prove sufficient balance without revealing actual amount
var (bProof, bSalt) = zkp.ProveBalance(1000.0, 500.0);
bool bValid = zkp.VerifyBalance(bProof, 500.0, bSalt, 1000.0);

For Bulletproofs (true ZKP):

using ZkpSharp.Security;

var zkProvider = new BulletproofsProvider();
var (proof, commitment) = zkProvider.ProveRange(value: 42, min: 0, max: 100);
bool valid = zkProvider.VerifyRange(proof, commitment, min: 0, max: 100);

See QUICKSTART.md for a complete walkthrough including Stellar integration.

API

Zkp -- HMAC-based privacy proofs

All Prove* methods return (string Proof, string Salt). Salts are generated automatically and must be stored alongside proofs.

BulletproofsProvider -- True zero-knowledge proofs

Prove* methods return (byte[] proof, byte[] commitment).

StellarBlockchain -- On-chain verification

var blockchain = new StellarBlockchain(
    serverUrl: "https://horizon-testnet.stellar.org",
    sorobanRpcUrl: "https://soroban-testnet.stellar.org",
    hmacKey: hmacKey
);

bool result = await blockchain.VerifyBalanceProof(contractId, proof, balance, required, salt);

SorobanTransactionBuilder -- Manual transaction construction

var builder = new SorobanTransactionBuilder(Network.Test());

// HMAC proof verification
string xdr = builder.BuildVerifyProofTransaction(contractId, proof, data, salt, hmacKey);

// ZK proof verification
string zkXdr = builder.BuildVerifyZkRangeProofTransaction(contractId, proof, commitment, min, max);
string ageXdr = builder.BuildVerifyZkAgeProofTransaction(contractId, proof, commitment, minAge);
string balXdr = builder.BuildVerifyZkBalanceProofTransaction(contractId, proof, commitment, required);

Soroban contract

The Rust smart contract (contracts/stellar/contracts/proof-balance/) exposes the following functions:

See contracts/stellar/README.md for contract details and contracts/stellar/DEPLOYMENT.md for deployment instructions.

Architecture

Application
  |
  +-- Zkp (HMAC proofs)
  +-- BulletproofsProvider (ZK proofs)
  |
  +-- StellarBlockchain
        +-- SorobanTransactionBuilder --> XDR
        +-- SorobanRpcClient --> Soroban RPC --> ZkpVerifier Contract

Security

• Key management: Use environment variables for development. Use Azure Key Vault, AWS Secrets Manager, or HashiCorp Vault in production.
• Salts: Never reuse. ZkpSharp generates cryptographically secure random salts automatically.
• Contract verification: Always verify deployed contract code matches source.
• Transaction fees: Soroban transactions require XLM.

Documentation

Contributing

1. Fork the repository
2. Create a branch (git checkout -b feature/your-feature)
3. Run tests (dotnet test)
4. Submit a pull request

License

MIT License. See LICENSE for details.

Contact

sagynbaev6@gmail.com | GitHub Issues | NuGet