DayKey

DayKey is a date-based credentialing scheme for ephemeral cryptographic keys used in access control and data protection. It generates a unique key for each calendar day by deriving it from a protected master seed and the date, so the same origin yields the same key on any device at the same date. The daily rotation limits exposure and simplifies enforcement of time-bound policies.

Derivation and use: A common approach is to compute daily_key = KDF(master_seed, date) using an HMAC-based function. The resulting key can serve as a symmetric encryption key, or as a prerequisite for signing or validating short-lived tokens. DayKey emphasizes secure seed storage, typically in a hardware security module or secure element, with local derivation to avoid distributing the seed.

Applications and considerations: DayKey is used for per-day API access, temporary file encryption, and audit-friendly session credentials. It supports revocation and rollover by rotating the master seed. Time synchronization and robust seed protection are critical; compromise of the seed compromises all keys derived from it for all dates unless a new seed is rolled. Some variants discuss cross-organization sharing; governance and compliance considerations apply.

See also: time-based keys, key derivation functions, one-time password.