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codes from runs
M6's step sizes were estimates, only exercised with small codes. With the
largest inputs the app accepts, every 2D encoder tripped the watchdog on
the Forerunner 255S (and the biggest steps were far over the 768 KB
watches' limit), so a large code added from the phone would have stopped
the app during settings processing at every start.
- QR: resumable segmentation, Reed-Solomon, interleaving, function
patterns and final mask; mask scoring on rows and columns packed 16
modules per word (same penalties, checked against the per-module rules).
- Reed-Solomon: resumable field tables and generator, encoder shifting
with native slice.
- Data Matrix, Aztec, PDF417: resumable encodation, stuffing, compaction,
placement and build; Data Matrix's grid as a byte array (90 KB -> 35 KB);
PDF417 refuses text that can't fit the screen before compacting.
- Cache format 2 with 16-bit sizes (wide PDF417 was cached wrong); packing
in steps; codes drawn as runs, and from a bitmap painted in steps when a
frame can't draw all runs.
- The job runner does two steps per tick on 768 KB watches;
gen_products --check verifies each product's watchdogCount fits that.
- CodeView renews full brightness (AMOLED) or the backlight (MIP) for up to
a minute from its single ticker; a tap restarts the minute.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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- Sha512: FIPS 180-4 in Monkey C (no native SHA-512), rotations inlined
with precomputed masks; constants derived from the primes, not typed.
- Hmac: RFC 2104 over SHA-1/256/512 (native HMAC only supports SHA-256).
- Kdf: resumable PBKDF2-HMAC-SHA256 job with calibration bounds
(2,000-200,000 iterations) and HKDF-SHA256.
- Aes: CBC with PKCS#7 over the native cipher; AES-256 chosen.
- SealedBox: encrypt-then-MAC records (HKDF-split keys, length-prefixed
aad, constant-time tag check before decryption).
- SelfTest: known-answer tests for every primitive at start-up.
- Bytes (wipe, constant-time equal), Clock (2038-safe widening, trusted
clock), Jobs (bounded steps against the watchdog, timer runner).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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