Table of Contents

• What it does
• Install
• Usage
• Ciphers
• Build from source
• Shell completions
• Wire format
• Security notes
• Related
• License

lvthn encrypts and decrypts files and pipes from the command line. One keyfile works with all three ciphers; the header byte chooses the algorithm on decrypt automatically. Encryption and decryption distribute 64KB chunks across a worker pool sized to hardwareConcurrency, and each worker owns an isolated WASM instance with no shared memory between workers. Output is byte-compatible with the web demo.

Installs the lvthn command globally.

bun add -g lvthn
# or
npm install -g lvthn

# Encrypt with a passphrase (Serpent by default)
lvthn encrypt -p "correct horse battery" secret.txt

# Encrypt with XChaCha20-Poly1305
lvthn encrypt --cipher chacha -p "correct horse battery" secret.txt

# Encrypt with AES-256-GCM-SIV
lvthn encrypt --cipher aes -p "correct horse battery" secret.txt

# Encrypt with a keyfile
lvthn encrypt -k my.key secret.txt secret.enc

# Encrypt from stdin, armored output
cat secret.txt | lvthn encrypt -k my.key --armor > secret.enc

# Decrypt (cipher is detected automatically from the file)
lvthn decrypt -p "correct horse battery" secret.enc
lvthn decrypt -k my.key secret.enc decrypted.txt

# Generate a 256-bit keyfile
lvthn keygen
lvthn keygen --armor -o my.key

On decrypt, the --cipher flag is not needed. The cipher byte in the file header tells lvthn which algorithm was used.

Serpent has a larger security margin (32 rounds versus 20) at the cost of speed. ChaCha20-Poly1305 is the choice of TLS 1.3 and WireGuard. AES-GCM-SIV (RFC 8452) is nonce-misuse-resistant and benefits from hardware AES instructions where available. All three are good; pick based on your threat model and throughput requirements.

Throughput figures are approximate, measured pre-SIMD on Apple Silicon. Current leviathan-crypto releases include SIMD-accelerated paths for both ciphers, so actual numbers run higher on SIMD-capable hardware and vary by platform.

All three ciphers share the same outer format, the same scrypt key derivation, and the same keyfiles. A key generated with lvthn keygen works with any cipher.

Requires Bun.

bun install
bun bake
# → dist/lvthn

lvthn ships completion support for bash, zsh, fish, and PowerShell.

# zsh
echo 'source <(lvthn completion zsh)' >> ~/.zshrc
# or drop into a fpath directory
lvthn completion zsh > $(brew --prefix)/share/zsh/site-functions/_lvthn

# bash
lvthn completion bash > /usr/local/etc/bash_completion.d/lvthn

# fish
lvthn completion fish > ~/.config/fish/completions/lvthn.fish

# PowerShell
lvthn completion pwsh >> $PROFILE

Completions cover subcommands, flags, cipher values, and file paths. The --passphrase and --keyfile flags are mutually exclusive; once one is used the other is suppressed from suggestions.

LVTHN v3 binary format, shared with the web demo. The cipher byte at offset 6 of the header drives decryption automatically. See FORMAT.md for the full wire specification, including the pool preamble layout and the counter-nonce scheme.

• Key derivation. Passphrases go through scrypt (N=32768, r=8, p=1) with a fresh random 32-byte salt per encryption, producing a 32-byte master key. Keyfiles are read directly as 32 raw bytes.
• Parallelism. Encryption and decryption distribute 64KB chunks across a worker pool sized to hardwareConcurrency. Each worker owns an isolated WASM instance with no shared memory between workers.
• Integrity. Any modification to a ciphertext chunk fails that chunk's authentication. The entire decryption is rejected; no partial plaintext is produced.

• leviathan-crypto: the underlying library
• web demo, tamper demo, kyber demo, jwt demo
• FORMAT.md: LVTHN wire format specification
• npmjs.org/package/lvthn: published package

Leviathan and its demos are written under the MIT license.

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