---
phase: 01-format-specification
verified: 2026-02-24T21:15:00Z
status: passed
score: 6/6 must-haves verified
re_verification: false
---

# Phase 1: Format Specification Verification Report

**Phase Goal:** A complete, unambiguous binary format document that all three implementations can build against
**Verified:** 2026-02-24T21:15:00Z
**Status:** PASSED
**Re-verification:** No -- initial verification

## Goal Achievement

### Observable Truths

| # | Truth | Status | Evidence |
|---|-------|--------|----------|
| 1 | Format spec document exists at docs/FORMAT.md with complete byte-level definitions | VERIFIED | File exists, 1031 lines, 13 sections covering header (40 bytes, 8 fields with offsets), file table entry (11 fields with sizes/types/endianness), and data blocks |
| 2 | Every binary structure (header, file table entry, data block) has a field table with offset, size, type, endianness, and description | VERIFIED | Header field table at lines 114-123 (8 rows, all columns present). File table entry field table at lines 145-157 (11 rows, all columns). Data block layout at Section 6 with ciphertext-only specification. |
| 3 | Encryption parameters are fully specified: AES-256-CBC, IV storage, HMAC-SHA-256 scope (IV \|\| ciphertext), PKCS7 padding formula | VERIFIED | Section 7 (lines 211-293): AES-256-CBC with 32-byte key, 16-byte random IV per file. HMAC input explicitly defined as "IV (16 bytes) \|\| ciphertext (encrypted_size bytes)" in 3 locations (lines 275, 523, 565). PKCS7 formula with 8 examples (lines 260-267). No ambiguous phrases. |
| 4 | A worked example shows a concrete 2-file archive with every byte annotated | VERIFIED | Section 12 (lines 468-681): 2 files (hello.txt, data.bin), 323-byte archive. Per-file pipeline walkthrough, field-by-field hex tables for both TOC entries, annotated hex dump of entire archive, shell decode walkthrough with exact dd commands. Real SHA-256 hashes verified against sha256sum. |
| 5 | Obfuscation features (XOR headers, encrypted TOC, decoy padding) are fully specified with byte ranges and activation flags | VERIFIED | Section 9 (lines 319-387): XOR obfuscation with specific 8-byte key (0xA5 0x3C 0x96 0x0F 0xE1 0x7B 0x4D 0xC8), byte range 0x00-0x27, bootstrapping algorithm. TOC encryption with toc_iv, PKCS7, size tracking. Decoy padding with per-file padding_after field. All controlled by flags bits 1-3. No "see Phase 6" deferrals. |
| 6 | Shell decoder reference functions (LE integer reading, HMAC verification) are included in appendix | VERIFIED | Section 13 (lines 814-1031): read_le_u16(), read_le_u32() with xxd and od fallbacks, read_hex(), verify_hmac(), decrypt_file(), verify_sha256(). Also includes Kotlin reference (decryptFileEntry, verifyHmac, decompressGzip, verifySha256) with full decode flow. |

**Score:** 6/6 truths verified

### Required Artifacts

| Artifact | Expected | Status | Details |
|----------|----------|--------|---------|
| `docs/FORMAT.md` | Complete binary format specification, min 300 lines, contains "Archive Header" | VERIFIED | 1031 lines, "Archive Header" appears 2 times, all 13 sections present. No stubs or placeholders. |

### Key Link Verification

| From | To | Via | Status | Details |
|------|-----|-----|--------|---------|
| Header definition (Section 4) | Worked example (Section 12.5) | Offset consistency (0x00-0x27) | VERIFIED | All 8 header fields in the worked example table (lines 596-603) use the exact same offsets as the definition table (lines 116-123). Python script verified all field positions. |
| File table entry definition (Section 5) | Worked example (Sections 12.6-12.7) | Field sizes match TOC entry byte count | VERIFIED | Entry 1: 2 + 9 + 4 + 4 + 4 + 4 + 16 + 32 + 32 + 1 + 2 = 110 bytes, offsets 0x28-0x95. Entry 2: 2 + 8 + 4 + 4 + 4 + 4 + 16 + 32 + 32 + 1 + 2 = 109 bytes, offsets 0x96-0x102. Both verified by Python script against every individual field offset. |
| Shell walkthrough dd skip values | Archive byte offsets | Skip matches hex offset | VERIFIED | All 15 dd commands in Section 12.10 use skip values that exactly match the documented byte offsets (verified programmatically). |

### Requirements Coverage

| Requirement | Source Plan | Description | Status | Evidence |
|-------------|------------|-------------|--------|----------|
| FMT-05 | 01-01-PLAN.md | Format specification as a document (before implementation starts) | SATISFIED | `docs/FORMAT.md` created with 1031 lines before any code. Commits `fcd37f5` and `1c698fe` both confirmed in git log. REQUIREMENTS.md marks FMT-05 as Complete. |

No orphaned requirements -- only FMT-05 is mapped to Phase 1 in the REQUIREMENTS.md traceability table.

### Anti-Patterns Found

| File | Line | Pattern | Severity | Impact |
|------|------|---------|----------|--------|
| `docs/FORMAT.md` | 653 | "representative placeholders" (in hex dump description) | Info | Expected and acceptable -- gzip and AES ciphertext are non-deterministic, so representative bytes are used. SHA-256 hashes are verified real values. No impact on spec unambiguity. |

No TODO, FIXME, TBD, HACK, "see Phase 6", "coming soon", or "will be here" found anywhere in the document.

### Human Verification Required

### 1. Hex Dump Annotation Alignment

**Test:** Read through the annotated hex dump (Section 12.9) and verify that each row's annotation correctly describes the bytes at that offset.
**Expected:** Every annotation label matches the field at that byte position per the field tables in Sections 4-5.
**Why human:** Visual alignment verification is difficult to automate given the formatted markdown table.

### 2. Spec Standalone Comprehensibility

**Test:** Give the spec to a developer unfamiliar with the project and ask them to implement a minimal header parser without asking questions.
**Expected:** The developer can write a parser using only the information in the document.
**Why human:** Assessing whether the document is unambiguous from a reader's perspective requires human judgment.

### Gaps Summary

No gaps found. All 6 observable truths are verified. The format specification document is complete, internally consistent, and unambiguous:

- All binary structures have field tables with exact byte offsets, sizes, types, and endianness
- SHA-256 hashes in the worked example are verified correct
- All worked example offsets are internally consistent (verified by Python script tracing every field)
- Shell decode dd skip values match documented offsets
- HMAC input is explicitly defined in 3 locations with no ambiguity
- PKCS7 formula has 8 worked examples
- Obfuscation features are fully specified with no deferrals to Phase 6
- Shell and Kotlin reference code included in appendix
- No anti-pattern blockers or warnings
- Commits `fcd37f5` and `1c698fe` confirmed in git history

---

_Verified: 2026-02-24T21:15:00Z_
_Verifier: Claude (gsd-verifier)_
