android-encrypted-archiver/.planning/phases/02-core-archiver/02-01-SUMMARY.md

phase, plan, subsystem, tags, requires, provides, affects, tech-stack, key-files, key-decisions, patterns-established, requirements-completed, duration, completed

phase	plan	subsystem	tags	requires	provides	affects	tech-stack	key-files	key-decisions	patterns-established	requirements-completed	duration	completed
02-core-archiver	01	crypto, format, cli	aes-256-cbc hmac-sha256 gzip clap flate2 pkcs7 binary-format	phase provides 01-format-spec FORMAT.md binary format specification (byte-level field definitions)	Rust project with Cargo.toml and all crypto/compression/format dependencies CLI skeleton with pack/unpack/inspect subcommands (clap derive) Binary format types (Header, TocEntry) with serialize/deserialize matching FORMAT.md AES-256-CBC encrypt/decrypt pipeline with PKCS7 padding HMAC-SHA-256 compute/verify (encrypt-then-MAC over IV||ciphertext) SHA-256 hash for file integrity verification Gzip compress/decompress with deterministic mtime(0) Compression heuristic for known compressed file extensions Hardcoded 32-byte AES key constant	02-core-archiver 03-round-trip-verification	added patterns aes 0.8 cbc 0.1 hmac 0.12 sha2 0.10 flate2 1.1 clap 4.5 rand 0.9 anyhow 1.0 manual binary serialization with to_le_bytes/from_le_bytes RustCrypto type aliases for cipher modes GzBuilder mtime(0) for reproducibility	created modified Cargo.toml src/main.rs src/cli.rs src/key.rs src/format.rs src/crypto.rs src/compression.rs src/archive.rs	Used rand::Fill::fill() instead of try_fill() for IV generation (correct rand 0.9 API) Edition 2021 to match plan specification Dead-code warnings expected and acceptable until pack/unpack/inspect wire up modules in Plan 02-02	Type aliases for cipher modes: type Aes256CbcEnc = cbc::Encryptor<aes::Aes256> Manual binary serialization: to_le_bytes()/from_le_bytes() for all multi-byte fields HMAC-SHA-256 scope: IV (16 bytes) || ciphertext (encrypted_size bytes) Compression heuristic: extension-based auto-detection + CLI override via --no-compress GzBuilder::new().mtime(0) for deterministic gzip output	FMT-01 FMT-02 FMT-03 FMT-04 ENC-01 ENC-02 ENC-03 ENC-04 ENC-05 CMP-01 CMP-02 INT-01 CLI-01	4min	2026-02-24

Phase 2 Plan 1: Project Foundation Summary

Rust project with AES-256-CBC/HMAC-SHA-256 crypto pipeline, binary format serialization matching FORMAT.md, gzip compression, and clap CLI skeleton

Performance

• Duration: 4 min
• Started: 2026-02-24T20:54:36Z
• Completed: 2026-02-24T20:58:28Z
• Tasks: 2
• Files modified: 8

Accomplishments

• Complete Rust project structure with 7 source modules and all dependencies
• Binary format types (Header: 40 bytes, TocEntry: 101+N bytes) with byte-accurate serialization matching FORMAT.md Sections 4 and 5
• Full crypto pipeline: AES-256-CBC encrypt/decrypt, HMAC-SHA-256 compute/verify, SHA-256 hash, random IV generation
• Gzip compression/decompression with reproducible output and smart compression heuristic

Task Commits

Each task was committed atomically:

1. Task 1: Project scaffolding with Cargo, CLI skeleton, and key module - c647f3a (feat)
2. Task 2: Format types, crypto pipeline, and compression module - 6292b41 (feat)

Files Created/Modified

• Cargo.toml - Project manifest with aes, cbc, hmac, sha2, flate2, clap, rand, anyhow
• src/main.rs - CLI entry point with clap parse and dispatch to pack/unpack/inspect
• src/cli.rs - Clap derive structs: Cli, Commands enum (Pack/Unpack/Inspect)
• src/key.rs - Hardcoded 32-byte AES-256 key constant
• src/format.rs - Header and TocEntry structs with write/read serialization, entry_size, compute_toc_size
• src/crypto.rs - encrypt_data, decrypt_data, compute_hmac, verify_hmac, sha256_hash, generate_iv
• src/compression.rs - compress, decompress, should_compress
• src/archive.rs - Stub module for pack/unpack/inspect orchestration (Plan 02-02)

Decisions Made

• Used rand::Fill::fill() instead of try_fill() for IV generation (correct rand 0.9 API for array fill)
• Kept edition 2021 as specified in the plan for broad compatibility
• Dead-code warnings are expected and acceptable -- modules are not yet called from main; they will be wired in Plan 02-02

Deviations from Plan

Auto-fixed Issues

1. [Rule 3 - Blocking] Fixed rand 0.9 API for IV generation

• Found during: Task 2 (crypto.rs implementation)
• Issue: try_fill() method does not exist on [u8; 16] in rand 0.9. The Fill trait provides fill(), not try_fill().
• Fix: Changed from iv.try_fill(&mut rand::rng()) to rand::Fill::fill(&mut iv, &mut rand::rng())
• Files modified: src/crypto.rs
• Verification: cargo build succeeds
• Committed in: 6292b41 (Task 2 commit)

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Total deviations: 1 auto-fixed (1 blocking) Impact on plan: Minor API correction for rand 0.9. No scope creep.

Issues Encountered

None beyond the rand API correction noted above.

User Setup Required

None - no external service configuration required.

Next Phase Readiness

• All building-block modules are implemented and compile successfully
• Ready for Plan 02-02: Pack, inspect, and unpack commands with full archive orchestration
• The archive.rs module is a stub awaiting the orchestration logic
• 25 dead-code warnings will be resolved when modules are wired into commands

Self-Check: PASSED

All 8 created files verified present. Both task commits (c647f3a, 6292b41) verified in git log.

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Phase: 02-core-archiver Completed: 2026-02-24