OSS-SO (Standard Offline)

OSS Association standard for offline-capable electronic access control. Defines a vendor-neutral data layout that lets credentials issued by one vendor interoperate with locks and readers from another, without requiring online communication between them at authentication time.

Two reference parts are typically asked about — OSS-SO Part II (data layout) and OSS-SO Part III (cryptography). A separate "Wallet extension" defines how OSS-SO payloads are carried inside Apple / Google Wallet passes.

Common in EU access control — customers in that market frequently ask whether a credential provider supports OSS-SO interop. LEGIC Connect supports payloads formatted per the latest OSS-SO Wallet extension; Parts II/III specifically were asked but not separately confirmed (see Wiki — Open Questions).