Unsecure computational environments threaten many financial cryptography implementations, and other sensitive computation. High-performance secure coprocessors can address these threats. However, using this technology for practical security solutions requires overcoming numerous technical and business obstacles. These obstacles motivate building a high-performance secure coprocessor that balances security with easy third-party programmability—but these obstacles also provide many design challenges. This paper discusses some of issues we faced when attempting to build such a device.