Annex A.1: Deoxys-TBC-256 example

What the clause requires

What the public text does not state

• The example values
• Any amendment change to the example

What it means for you

The 256-bit Deoxys example is the one most implementers reach for first, because it fits a 128-bit key and a 128-bit tweak exactly. The block is 128 bits, the tweakey is 256 bits, and clause 6 fixes the round count at 14. The annex supplies a worked input and output so a implementation can be checked without reading the round function line by line.

A single vector is a narrow test. It proves that one path through the implementation produces the published result; it does not prove that every key, tweak or input does. The record treats it as the first evidence line and pairs it with a code review of the round order and the final sub-tweakey step. That pairing is what an evaluator will look for.

The buyer question is not "does the vector pass" but "can you show me the record". The five fields are the algorithm, the input, the key, the tweak and the expected output, plus the build tested. A test record with those fields can be repeated by a reviewer. A screenshot of a green tick cannot.

Evidence to keep

What an auditor or a customer is likely to ask for

Artefact	Owner	Why it matters
Known-answer test record for Deoxys-TBC-256 with input, key, tweak, output and build	Engineering	The informative annex is the standard own check.
Configuration record showing a key of at least 128 bits and the remainder as tweak	Engineering	The 256-bit name does not fix the key length.
Code review note on the 14-round order and the final sub-tweakey step	Security architecture	A vector can pass with a compensating error elsewhere.

How to verify it

Ask for the Deoxys-TBC-256 test record. Check that the key and tweak lengths add to 256 and that the key is at least 128.

Dates

The kit plan for annex A.1 sets the evidence review at 17 June 2027, 90 days before the estimated publication date of 15 September 2027.

Cross references

• A Annex A, Numerical examples
• 5 Requirements on the usage of tweakable block ciphers
• 6.1 Deoxys-TBC versions
• 6.2 Deoxys-TBC encryption

Where this comes from