Clause 6.4: Deoxys-TBC tweakey schedule

What the clause requires

What the public text does not state

• The entire body of clause 6.4
• Any amendment change to the schedule

What it means for you

This page exists so that the record has no hole. The document has a subclause that derives the per-round sub-tweakeys for Deoxys-TBC, and the ISO public preview stops before it. Rather than describe it from memory or from a paper about the cipher, the record states the title, the page and the fact that the text is not in the public preview.

That honesty has a practical value. An implementation review has to cover the schedule, because the schedule is where the key and tweak are loaded and where the round constants are applied. The questions to put to the engineering team are the same questions the published clause will answer: how the tweakey is divided, how the sub-tweakey is updated each round, and how the tweak length changes the update.

The evidence line is therefore a request, not a finding. Ask for the design note that traces the schedule, and for the known-answer test that exercises more than one round. When the purchased text is available, this page is replaced with a statement of the clause and the register is reissued at no extra charge to kit buyers.

Evidence to keep

What an auditor or a customer is likely to ask for

Artefact	Owner	Why it matters
Design note tracing the sub-tweakey derivation to the implementation	Engineering	The schedule is where key and tweak handling is visible.
Known-answer test that exercises multiple rounds and both directions	Engineering	A one-round test would not catch a schedule defect.
Purchase record for the base standard, so clause 6.4 can be read in full	Standards owner	The page states that the text is not in the public preview until it is bought or licensed.

How to verify it

Ask whether the review covered the schedule. If the answer cites a paper or a blog rather than the standard, the trace is not to the text.

Dates

The kit plan for clause 6.4 sets the evidence review at 17 June 2027, 90 days before the estimated publication date of 15 September 2027.

Cross references

• 6 Deoxys-TBC
• 6.1 Deoxys-TBC versions
• 6.2 Deoxys-TBC encryption
• A.1 Deoxys-TBC-256 example
• A.2 Deoxys-TBC-384 example

Where this comes from