Despite decades of effort, a persistent chasm has existed between the theory and practice of device-level biometric authentication. Theoretical constructions can, in principle, provide biometric authentication with cryptographically secure public enrollment data. However, concrete implementations of these techniques have failed to provide security with real-world parameters. The result is that deployed authentication algorithms rely on data that overtly leaks private information about the biometric; thus systems rely on externalized security measures such as trusted execution environments.