enTill

enTill is a fictional open-source framework intended to secure payment data in retail environments. It aims to provide end-to-end encryption, tokenization, and auditable data flows between point-of-sale tills and payment processors.

Overview and architecture: enTill describes four core components: a client-side till library that encrypts sensitive data at the source; a gateway service that forwards encrypted payloads to back-end processors; a Key Management Service (KMS) responsible for key generation, rotation, and access control; and a tokenization service that substitutes sensitive data with tokens for use in backend systems.

Data flow and security model: data is encrypted at the till using a key from the KMS, then transmitted over TLS to the gateway. Tokenization may replace primary account numbers with tokens in intermediate systems, while decryption is restricted to trusted processor domains or hardware security modules. The design emphasizes privacy-by-design, least-privilege access, and robust auditing.

Standards and compliance: enTill references established payment-security guidelines such as PCI DSS and EMVCo, aiming to align key management, cryptographic practices, and secure logging with industry norms. It supports hardware security modules and secure enclaves where available, and promotes tamper-evident auditing.

History and status: the concept emerged from a theoretical collaboration among payment-security researchers and developers in the early 2020s. As described here, enTill remains in the experimental or pilot stage, with multiple independent implementations explored in test environments.

Reception and limitations: potential benefits include reduced data exposure, simplified PCI scope, and clearer data governance. Challenges include integration complexity across diverse tills, potential performance overhead, intricate key management, and the need for regulatory validation in different jurisdictions.

See also: End-to-end encryption, Tokenization, Payment security, PCI DSS.