detssh 0.1.0

Deterministic Ed25519 SSH key generation from a seed passphrase, via configurable KDF and salt-hash backends.

detssh

Deterministic Ed25519 SSH key generation from a seed passphrase. Same passphrase + same parameters → same keypair, every time, on any machine - nothing to back up but what's in your head.

detssh

Prompts for everything (passphrase hidden + confirmed) and writes to the same place ssh-keygen would: ~/.ssh/id_ed25519 / ~/.ssh/id_ed25519.pub (mode 600/700, ~/.ssh created if missing). Pass --output to write somewhere else instead.

Non-interactively:

detssh --kdf argon2id --salt-algo blake2b --seed "..." --label github --overwrite-files

Any flag switches to non-interactive mode: missing optional fields fall back to their defaults, --seed is the only required one. Passing --seed on the command line puts it in your shell history and process list (ps aux) - fine for local scripting, but prefer the interactive prompt when that matters.

Backends

• --kdf: argon2id (default), argon2i, argon2d, scrypt, pbkdf2, bcrypt_pbkdf
• --salt-algo: blake2b (default), blake2s, sha256, sha384, sha512, sha3_256, sha3_384, sha3_512

Each combination has its own options (cost knobs, salt digest size, etc.), with their valid ranges shown in both --help and the interactive prompts. See them with:

detssh --kdf <kdf> --salt-algo <salt-algo> --help

We recommend sticking with the defaults (argon2id, memory-hard with a high cost) unless you have a specific reason not to - they make brute-forcing your passphrase significantly more expensive than faster KDFs like pbkdf2.

Cost knobs (iterations, memory, cost, rounds, ...) also carry a soft safety limit meant to catch typos before they cost you minutes of derivation time. In interactive mode, going over one doesn't interrupt you - everything you exceeded is summarized in one confirmation at the very end. In flag mode, it fails immediately unless you pass --force-allow-soft-constraints.

Determinism guarantee

Same explicit parameters → same key, across any release sharing the same major version - only a major version bump may change key derivation. That guarantee starts at 1.0; we're still on 0.x, so it doesn't apply yet (see tests/golden/README.md).

Development

uv sync
uv run pytest
uv run ruff check .