Zupt

Backup compression with AES-256 authenticated encryption and post-quantum key encapsulation.

Zupt compresses and encrypts backup archives. LZ77+Huffman compression, AES-256-CTR + HMAC-SHA256 per-block authentication, multi-threaded, and optional ML-KEM-768 + X25519 post-quantum hybrid encryption. Pure C11, zero dependencies, ~5,000 lines.

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Why Zupt

• Post-quantum encryption (v0.7+). --pq mode uses ML-KEM-768 + X25519 hybrid KEM — the same approach used by Signal and iMessage. Protects against "harvest now, decrypt later" quantum attacks.
• Encrypted backups in one command. zupt compress -p backup.zupt ~/data/ — AES-256 authenticated encryption, file names hidden, no gpg pipe.
• Multi-threaded. -t 0 auto-detects cores. Batch-parallel compression pipeline.
• Per-block integrity. XXH64 checksum + HMAC-SHA256 per block. Wrong password/key rejected instantly.
• Zero dependencies. ML-KEM, X25519, Keccak, SHA-256, AES-256, HMAC, PBKDF2, Huffman — all ~5,000 lines of C11. Builds with gcc or cl alone.
• Compression on par with gzip. (Benchmarks →)

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Quick Start

# Build
git clone https://github.com/cristiancmoises/zupt.git && cd zupt && make

# Password-encrypted backup
zupt compress -p backup.zupt ~/Documents/
zupt extract -o ~/restored/ -p backup.zupt

# Post-quantum encrypted backup
zupt keygen -o mykey.key                              # Generate keypair
zupt keygen --pub -o pub.key -k mykey.key             # Export public key
zupt compress --pq pub.key backup.zupt ~/Documents/   # Encrypt with public key
zupt extract --pq mykey.key -o ~/restored/ backup.zupt # Decrypt with private key

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Post-Quantum Encryption

v0.7.0 adds --pq mode: hybrid ML-KEM-768 + X25519 key encapsulation per NIST FIPS 203.

Recipient's public key → ML-KEM-768 Encaps + X25519 ECDH → hybrid shared secret
                        → SHA3-512(ss ‖ transcript) → enc_key[32] + mac_key[32]
                        → AES-256-CTR + HMAC-SHA256 per block (unchanged from password mode)

Security model: Secure if EITHER ML-KEM-768 (post-quantum) OR X25519 (classical) is secure. Both must be broken to compromise the archive.

Password mode (-p) is NOT quantum-safe. Use --pq for long-term protection.

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Benchmark Results

Zupt vs gzip vs zstd — Level 7

File Type	Zupt L7	gzip -6	zstd -7
English text	629 KB (3.3:1)	643 KB (3.3:1)	638 KB (3.3:1)
JSON data	296 KB (7.1:1)	281 KB (7.5:1)	242 KB (8.7:1)
Server logs	908 KB (3.5:1)	839 KB (3.7:1)	797 KB (3.9:1)
Sparse binary	467 KB (2.2:1)	478 KB (2.2:1)	463 KB (2.3:1)

Ratio ≈ gzip. Zupt's value: encryption + integrity + PQ protection + zero dependencies.

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Feature Comparison

Feature	Zupt	gzip	zstd	7-Zip
Compression ratio	≈ gzip	Baseline	2–3× better	2–3× better
Multi-threaded	✓	✗ (pigz)	✓	✓
Post-quantum encryption	✓ (ML-KEM-768)	✗	✗	✗
Password encryption	AES-256 + HMAC	✗	✗	AES-256
Integrity	XXH64 per-block	CRC32	XXH64	CRC32
Recursive backup	✓	✗	✗	✓
Zero dependencies	✓	✓	✗	✗
License	MIT	GPL	BSD	LGPL

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Security

Password mode:  Password → PBKDF2-SHA256 (600K iter) → enc_key + mac_key
PQ hybrid mode: Public key → ML-KEM-768 Encaps + X25519 ECDH → enc_key + mac_key
Per-block:      AES-256-CTR(enc_key, nonce ⊕ seq) + HMAC-SHA256(mac_key)

See SECURITY.md for threat model. See AUDIT.md for audit checklist.

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Usage

zupt compress [OPTIONS] <output.zupt> <files/dirs...>
zupt extract  [OPTIONS] <archive.zupt>
zupt list     [OPTIONS] <archive.zupt>
zupt test     [OPTIONS] <archive.zupt>
zupt keygen   [-o file] [--pub] [-k privkey]
zupt bench    <files/dirs...>

Option	Description
-l <1-9>	Compression level (default: 7)
-t <N>	Thread count (0=auto, 1=single, 2–64)
-p [PW]	Password encryption (PBKDF2)
--pq <keyfile>	Post-quantum hybrid encryption
-o <DIR>	Output directory (extract)
-s	Store without compression
-f	Fast LZ codec
-v	Verbose
--solid	Solid mode

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Building

make                        # Linux/macOS
make test-all               # 16 regression tests
sh tests/test_threaded.sh   # 14 multi-threaded tests
sh tests/test_pq.sh         # 10 post-quantum tests
make test-asan              # AddressSanitizer
build.bat                   # Windows

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Roadmap

Version	Status	Description
v0.5	✅	Security hardening, Huffman codec fix
v0.6	✅	Multi-threaded compression
v0.7	✅	Post-quantum hybrid encryption (ML-KEM-768 + X25519)
v1.0	✅ Current	Stable release, format frozen, security audit

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License

MIT - see LICENSE.

Security vulnerabilities: see SECURITY.md.

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© 2026 Cristian Cezar Moisés - github.com/cristiancmoises