Shack Payment Gateway 0.1.0 Adds Ethereum Auth

The shack-payment-gateway package version 0.1.0 is now available as an MCP server that gates tool calls behind cryptographic micropayment authorization using Ethereum [1]. The software generates a unique EIP-191 challenge string containing a timestamp and nonce that a client must sign with their private key before accessing a paid tool [1].

Once the server receives the signature, it uses ECDSA key recovery to identify the signer's Ethereum address and compares it against a configured authorized wallet [1]. The system returns verified: true if the addresses match and verified: false otherwise, providing a binary check for tool access [1]. Operators can restrict access to a specific address using the SHACK_AUTHORIZED_WALLET environment variable or enable a permissive mode that accepts any valid signature [1].

The server communicates via JSON-RPC 2.0 over stdio, separating protocol messages on STDOUT from diagnostic logs on STDERR [1]. Unit tests cover EIP-191 hashing, ECDSA recovery, and address validation, while integration tests verify the end-to-end handshake and error handling [1].

This release provides a technical framework for developers to monetize or restrict access to MCP tools by requiring cryptographic proof of wallet ownership.