  Blockchain technologies provide excellent architectures and practical tools
for securing and managing the sensitive and private data stored in biometric
templates, but at a cost. We discuss opportunities and challenges in the
integration of blockchain and biometrics, with emphasis in biometric template
storage and protection, a key problem in biometrics still largely unsolved. Key
tradeoffs involved in that integration, namely, latency, processing time,
economic cost, and biometric performance are experimentally studied through the
implementation of a smart contract on the Ethereum blockchain platform, which
is publicly available in github for research purposes.
