Concept

KGT — Key Generation Time

KGT is the 15-minute time window that scopes every ASK in HexaEight. It is the Unix minute floored to the nearest 15.

Computing KGT

long nowMinutes = (long)(DateTime.UtcNow - DateTime.UnixEpoch).TotalMinutes;
long kgt        = nowMinutes - (nowMinutes % 15);

Why a window, not a moment?

• Clock skew tolerance — two parties whose clocks differ by < 15 min compute the same KGT, so handshake-free derivation just works.
• Rotation — every 15 minutes the ASK changes naturally. A leaked key is only useful for messages in its window.
• Replay window — receivers can reject envelopes whose KGT is too far in the past.

Overriding KGT

Most code lets the Bridge pick "now." Pass an explicit KGT to EncryptEnvelopeAsync when re-encrypting historical data, replaying flows, or running deterministic tests.

See also

• ASK — the key derived for a given KGT.
• Envelopes — where the KGT appears on the wire.