docs: Add README files & etc
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NikitolProject
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README.md
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# encrypted_archive
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[Русская версия (README_ru.md)](README_ru.md)
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Custom encrypted archive format designed to be **unrecognizable** by standard analysis tools (`file`, `binwalk`, `strings`, hex editors).
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## Features
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- **AES-256-CBC** encryption with per-file random IVs
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- **HMAC-SHA-256** authentication (IV || ciphertext)
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- **GZIP compression** with smart detection (skips already-compressed formats)
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- **XOR-obfuscated headers** — no recognizable magic bytes
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- **Encrypted file table** — metadata invisible in hex dumps
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- **Decoy padding** — random 64–4096 bytes between data blocks
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- **Three decoders**: Rust (native CLI), Kotlin (JVM/Android), Shell (POSIX)
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## Quick Start
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```bash
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# Build
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cargo build --release
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# Pack files into an archive
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./target/release/encrypted_archive pack file1.txt photo.jpg -o archive.bin
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# Inspect metadata (without extracting)
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./target/release/encrypted_archive inspect archive.bin
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# Extract files
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./target/release/encrypted_archive unpack archive.bin -o ./output/
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```
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## CLI Reference
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### `pack` — Create an encrypted archive
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```
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encrypted_archive pack <FILES>... -o <OUTPUT> [--no-compress <PATTERNS>...]
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```
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| Argument | Description |
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|----------|-------------|
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| `<FILES>...` | One or more files to archive |
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| `-o, --output` | Output archive path |
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| `--no-compress` | Skip compression for matching filenames (suffix or exact match) |
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Compression is automatic for most files. Already-compressed formats (`.zip`, `.gz`, `.jpg`, `.png`, `.mp3`, `.mp4`, `.apk`, etc.) are stored without recompression.
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```bash
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# Pack with selective compression control
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encrypted_archive pack app.apk config.json -o bundle.bin --no-compress "app.apk"
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```
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### `unpack` — Extract files
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```
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encrypted_archive unpack <ARCHIVE> [-o <DIR>]
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```
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| Argument | Description |
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|----------|-------------|
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| `<ARCHIVE>` | Archive file to extract |
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| `-o, --output-dir` | Output directory (default: `.`) |
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### `inspect` — View metadata
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```
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encrypted_archive inspect <ARCHIVE>
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```
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Displays header fields, file count, per-file sizes, compression status, and integrity hashes without extracting content.
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## Decoders
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The archive can be decoded by three independent implementations. All produce **byte-identical output** from the same archive.
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### Rust (native CLI)
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The primary implementation. Used via `unpack` subcommand (see above).
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### Kotlin (JVM / Android)
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Single-file decoder for JVM environments. No external dependencies — uses `javax.crypto` and `java.util.zip` from the standard library.
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**Standalone usage:**
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```bash
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# Compile
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kotlinc kotlin/ArchiveDecoder.kt -include-runtime -d ArchiveDecoder.jar
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# Decode
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java -jar ArchiveDecoder.jar archive.bin ./output/
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```
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**As a library in an Android project:**
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Copy `kotlin/ArchiveDecoder.kt` into your project source tree. All crypto and compression APIs (`javax.crypto.Cipher`, `javax.crypto.Mac`, `java.util.zip.GZIPInputStream`) are available in the Android SDK.
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To use as a library, call the decoding logic directly instead of `main()`:
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```kotlin
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// Example: decode from a file
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val archive = File("/path/to/archive.bin")
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val outputDir = File("/path/to/output")
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decode(archive, outputDir)
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// The decode() function handles:
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// 1. XOR header de-obfuscation
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// 2. TOC decryption
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// 3. Per-file AES decryption + HMAC verification
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// 4. GZIP decompression (if compressed)
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// 5. SHA-256 integrity check
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```
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No native `.so` required — pure Kotlin/JVM running on ART.
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### Shell (POSIX)
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Emergency decoder for POSIX systems **with OpenSSL installed**.
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```bash
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sh shell/decode.sh archive.bin ./output/
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```
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**Requirements:** `dd`, `openssl`, `sha256sum`, `gunzip`, and either `xxd` or `od`.
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> **Note:** This decoder requires `openssl` for AES and HMAC operations. It will **not** work on minimal environments like BusyBox that lack OpenSSL. For constrained environments, use the Rust or Kotlin decoder instead.
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## Format Specification
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Full binary format specification: **[docs/FORMAT.md](docs/FORMAT.md)**
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### Archive Layout (summary)
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```
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┌──────────────────────────┐ offset 0
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│ Header (40 bytes, XOR) │ magic, version, flags, toc_offset, toc_size, toc_iv, file_count
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├──────────────────────────┤ offset 40
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│ TOC (encrypted AES-CBC) │ file entries: name, sizes, offsets, IV, HMAC, SHA-256
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├──────────────────────────┤
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│ Data Block 0 │ AES-256-CBC(GZIP(plaintext))
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│ Decoy Padding (random) │ 64–4096 random bytes
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├──────────────────────────┤
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│ Data Block 1 │
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│ Decoy Padding (random) │
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├──────────────────────────┤
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│ ... │
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└──────────────────────────┘
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```
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### Flags Byte
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| Bit | Mask | Feature |
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|-----|------|---------|
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| 0 | `0x01` | At least one file is GZIP-compressed |
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| 1 | `0x02` | TOC is AES-256-CBC encrypted |
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| 2 | `0x04` | Header is XOR-obfuscated |
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| 3 | `0x08` | Decoy padding between data blocks |
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Standard archives with all features: flags = `0x0F`.
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## Security Model
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**What this provides:**
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- Confidentiality — AES-256-CBC encryption per file
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- Integrity — HMAC-SHA-256 per file (encrypt-then-MAC)
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- Content verification — SHA-256 hash of original plaintext
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- Anti-analysis — no recognizable patterns for `file`, `binwalk`, `strings`
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**What this does NOT provide:**
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- Key management — v1 uses a hardcoded key (v2 will use HKDF-derived subkeys)
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- Forward secrecy
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- Protection against targeted cryptanalysis (the XOR key is fixed and public)
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The obfuscation layer is designed to resist **casual analysis**, not a determined adversary with knowledge of the format.
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## Building from Source
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```bash
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# Debug build
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cargo build
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# Release build (optimized)
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cargo build --release
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# Run all tests (unit + integration + golden vectors)
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cargo test
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```
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### Running Cross-Validation Tests
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```bash
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# Kotlin decoder tests (requires kotlinc + java)
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bash kotlin/test_decoder.sh
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# Shell decoder tests (requires openssl + sha256sum)
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bash shell/test_decoder.sh
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```
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## Project Structure
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```
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encrypted_archive/
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├── src/
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│ ├── main.rs # CLI entry point
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│ ├── cli.rs # Clap argument definitions
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│ ├── archive.rs # Pack / unpack / inspect
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│ ├── format.rs # Binary format serialization
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│ ├── crypto.rs # AES-256-CBC, HMAC-SHA-256, SHA-256
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│ ├── compression.rs # GZIP + smart format detection
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│ └── key.rs # Cryptographic key
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├── kotlin/
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│ └── ArchiveDecoder.kt # JVM/Android decoder (single file)
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├── shell/
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│ └── decode.sh # POSIX shell decoder
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├── docs/
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│ └── FORMAT.md # Binary format specification (normative)
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└── tests/
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└── golden_vectors.rs # Known-answer tests
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```
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## License
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TBD
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