# Shack Payment Gateway 0.1.0 Adds Ethereum Auth

**Published:** 2026-05-21T16:06:03.000Z  
**Topic:** Ethereum  
**Sentiment:** neutral  
**Publisher:** TrendWatcher — https://www.trendwatcher.in/article/4f42cdba-e35c-41a2-93ba-40400fdb3a33

Shack Payment Gateway 0.1.0 is an MCP server that gates tool calls using Ethereum EIP-191 signatures, offering strict or permissive authorization modes.

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.

## Sources
1. Docs — [shack-payment-gateway 0.1.0 - Docs.rs](https://docs.rs/crate/shack-payment-gateway/latest)
2. Sezzle — [Buy Now Pay Later at Fit Shack | Split Payments No Interest](https://sezzle.com/shop/fit-shack/)
3. San Francisco Examiner — [Burger giant to pay $20K to repeatedly misgendered Bay Area worker](https://www.sfexaminer.com/news/shake-shack-must-pay-20k-to-misgendered-sf-trained-employee/article_4004bbe8-acb2-11ed-b2d6-5b0d4642f84f.html)
4. Discountdeals — [Shake Shack Coupons | 50% Off Discount Code | Jan 2025](https://www.discountdeals.ae/shakeshack)
5. Atom — [PaymentShack.com is for sale](https://www.atom.com/name/PaymentShack)

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Cite as: TrendWatcher, "Shack Payment Gateway 0.1.0 Adds Ethereum Auth", https://www.trendwatcher.in/article/4f42cdba-e35c-41a2-93ba-40400fdb3a33