DateKeys/README.md

# datekeys-go

Reference implementation in Go of the **DateKeys Protocol Specification
v0.10** ([`spec/`](spec/DateKeys_Protocol_Specification_v0.10.md)).
[Versión en español](README.es.md).

DateKeys encrypts data so that it can only be opened after a chosen instant.
The time condition comes from the drand **Quicknet** randomness beacon: data is
sealed with timelock encryption to a future round, and the round's BLS
signature, published by drand when the round arrives, is the key. Everything
that can be verified locally is verified locally; relays, caches and APIs are
untrusted transports.

> **Status: v0.x, pre-standard.** The specification is a draft and the API may
> change before v1.0.0. The code has not had an external cryptographic review
> yet (spec §75). Do not rely on it for high-value secrets.

## What it implements

| Object | Spec | Package |
|---|---|---|
| DateKey: date → round, canonical `dk1_…` string | §14–§19 | [`datekey`](datekey) |
| Provider Profile, pinned Quicknet profile, `profile_hash` | §10–§13 | [`profile`](profile) |
| Release sources, local BLS verification, drand relays | §45–§52 | [`provider`](provider), [`provider/drand`](provider/drand) |
| DateKeyCap `.dkc`: `time_only` and `time_and_key`, the files of format 3 | §20–§39, §61–§63 | [`capsule`](capsule) |
| Paths and texts of a head, with the Unicode 18.0.0 and best-fit tables | §29.5, §29.6 | [`internal/pathrule`](internal/pathrule) |
| DateKeys Access Key `.dkk` | §40–§44 | [`accesskey`](accesskey) |
| Extensions, the public note | §24.1, §54 | [`extension`](extension) |
| Author keys `dkauthor1…`, `alg` 1 | §29.9, §29.12 | [`authorkey`](authorkey), [`internal/ed25519strict`](internal/ed25519strict) |
| Signature with certificates (`alg` 2, CMS), time seal (RFC 3161) | §29.10, §29.11 | [`internal/cms`](internal/cms), [`internal/der`](internal/der), [`capsule`](capsule) |
| The extension `datekeys.capsule`: locator and envelope | §44.1 | [`locator`](locator) |
| Deterministic CBOR | §58 | [`codec`](codec) |
| Normative errors | §69 | [`errors.go`](errors.go) |
| CLI | — | [`cmd/datekeys`](cmd/datekeys) |

No cryptography is implemented here. Encryption is [age](https://age-encryption.org)
(`filippo.io/age`); the timelock is [tlock](https://github.com/drand/tlock)
(its exported core only); BLS verification is drand's. This module adds
framing, CBOR, bindings, verification rules and the flow, and it enforces the
stanza rules of the protocol inside the age identities, so that a file is never
accepted just because age could unwrap a key.

Not implemented on purpose: the Release API server and queue, storage and
delivery, and the TypeScript client (plan §2). The signature with
certificates and the seal check the cryptography, never who issued a
certificate or a seal, or whether it was revoked: that is for an official
validator (spec §29.10). Brainpool curves and national algorithms such as GOST
or SM2 are outside the table.

## Versions

Three version numbers, each with its own meaning:

| Version | Where | Changes when |
|---|---|---|
| Format | Inside the objects: the capsule format, the `VERSION` of the DKC1 prelude, 3 when written and 1 to 3 when read, which is also the schema version of CONTROL_CBOR; and 1 for the framing of DKK1 and the schema of the other objects, the head and security of format 3 included | The format changes. A reader rejects a version it does not know (spec §22, §70) |
| Specification | `datekeys.SpecVersion`, today `0.10`, and the tag `spec-v0.10` | The normative text changes. Spec §76 records each change with its case |
| Module | The tags of this Go module, `vX.Y.Z`, and `datekeys.Version()` | The API or the behaviour changes. Semantic versioning, with no stability promise before v1.0.0 |

`datekeys version` prints the module version, the specification and the Go toolchain. A binary built in a checkout shows the pseudo-version of its commit, for example `v0.0.0-20260928105528-9ac9cd952f04`.

Each release states what it covers, here and in the [CHANGELOG](CHANGELOG.md). The code of this branch, not yet released, covers:
- specification 0.10: it writes capsule format 3 and reads formats 1, 2 and 3;
- the pinned Quicknet profile, and any profile on the three drand schemes that tlock supports;
- encryption, inspection and opening, and the CLI;
- every shared vector and fixture of [`testdata/`](testdata).

The first tag, v0.1.0, comes once `go get` works from a clean machine.

## A capsule, in one picture

```text
.dkc = PRELUDE (16 B) || PUBLIC_HEADER (CBOR) || SEALED_CONTROL (age) || PAYLOAD_AGE (age, to EOF)

time_only:     SEALED_CONTROL = age(tlock round R → CONTROL_CBOR)
time_and_key:  SEALED_CONTROL = age(tlock round R → age(16 X25519 stanzas → CONTROL_CBOR))
CONTROL_CBOR = { header_binding = SHA-256(PRELUDE || PUBLIC_HEADER), I_PAYLOAD, extensions, L, padding rule }
PAYLOAD_AGE  = age(X25519 R_PAYLOAD → BODY || zeros up to P = rule(L)), streamed

BODY = AREA_LEN || SECURITY_LEN || HEAD_LEN (3 × uint32)
    || SECURITY_CBOR, zeros up to AREA_LEN (512)   signature and seal: empty in v0.10
    || HEAD_CBOR                                   salt, comment, declared author, the files
    || the files, one after another
```

This is format 3, the one `encrypt` writes (spec §22, §29.2). Its 16 stanzas
hold from 1 to 16 credentials and a dummy in each slot left, in a random
order, and its payload is padded to P, so that until the unlock date nobody
learns the number of credentials, the exact length L, the names of the files
or how many there are, beyond what P bounds (spec §29.1, §39, §55.2). Once
open, it gives files with their paths, sizes, SHA-256 and modification times,
a comment and a declared author, and the verdicts of its security area.
Format 2, that of v0.9, holds one content; format 1, that of v0.8.2, has one
stanza per credential and no padding. Readers still open both.

## CLI

```bash
go install g.activething.com/go/DateKeys/cmd/datekeys@latest
```

The module is served by the project's own Gitea, whose certificate Go does not
trust by default. Set `GOPRIVATE=g.activething.com` so that the Go proxy and
checksum database are bypassed for it, and either install the server's
certificate or, on a trusted network, set `GOINSECURE=g.activething.com`.

```bash
datekeys datekey resolve -at 2030-01-01T00:00:00Z
datekeys encrypt -at 2030-01-01T00:00:00Z -in letter.txt -out letter.dkc
datekeys encrypt -at 2030-01-01T00:00:00Z -in photos -in letter.txt -comment "For Ana" -author "Juan" -out gift.dkc
datekeys encrypt -at 2030-01-01T00:00:00Z -policy time_and_key -dkk gift.dkk -in photos -out gift.dkc
datekeys encrypt -at 2030-01-01T00:00:00Z -padding bloque256 -no-mtime -in letter.txt -out letter.dkc
datekeys author keygen -out author.key -pass-file pass.txt
datekeys encrypt -at 2030-01-01T00:00:00Z -in letter.txt -note "Letters from Lisbon" -sign author.key -sign-pass-file pass.txt -out letter.dkc
datekeys decrypt -in letter.dkc -out letter -expect-author dkauthor1...
datekeys inspect -in gift.dkc
datekeys decrypt -in gift.dkc -out gift -dkk gift.dkk
datekeys profile hash
datekeys version
```

`encrypt` never touches the network. Each `-in` is a file or a folder; a
folder gives its name as the first segment of its paths, as a browser does,
and is walked without following links, taking regular files only and leaving
out `.DS_Store`, `Thumbs.db`, `desktop.ini`, `._*` and `__MACOSX`. A path or
a text that breaks a rule of spec §29.5 or §29.6 is refused, naming the rule
and the character. The files keep their modification times unless
`-no-mtime`. The content is padded with the rule reforzado, or bloque256 if
asked (spec §29.1).
`inspect` runs only the pre-unlock checks (spec §63 steps 1–8): it never
requests a release and never uses a secret.
`decrypt` fetches the release from public drand relays and verifies it
locally. The files of a format 3 capsule go to the new folder `-out`, staged
inside it and moved into place only after every check passed (spec §56); a
capsule with only a comment creates no folder. It shows the verdicts first
and last, and the declared author, the comment and the paths as text of the
creator that nobody has checked, each line behind a `│ ` prefix and never
wider than the terminal (spec §29.7). Formats 1 and 2 still give one file.
Outputs are never overwritten.

`author keygen` makes an Ed25519 author key (spec v0.11, §29.12) in a file
encrypted with a passphrase, or as text with `-plain`, and prints its public
key, `dkauthor1…`; `author public` prints it again. `encrypt -sign` signs the
capsule with it (`alg` 1) and checks the signature before writing anything;
`decrypt` shows the signature, and with `-expect-author` it fails, after
writing the files, unless the capsule is signed with that public key. The
passphrase comes from a file, or from the standard input with `-`, never from
the command line or the environment. `encrypt -note` puts a public note in
clear in the capsule (§24.1): `inspect` and `decrypt` show it as text of the
creator that nobody has checked.

## Library

```go
reg, err := profile.Default() // pinned Quicknet profile, checked against its profile_hash

// EncryptFiles: no network, the round is resolved locally. It reads each
// file twice, and fails if a file changes between the two readings.
res, err := capsule.EncryptFiles(dst, []capsule.Source{{
	Path:    "photos/beach.jpg",
	Size:    info.Size(),
	ModTime: info.ModTime(),
	Open:    func() (io.ReadCloser, error) { return os.Open(name) },
}}, capsule.EncryptOptions{
	Profile:        profile.Quicknet(),
	UnlockAt:       time.Date(2030, 1, 1, 0, 0, 0, 0, time.UTC),
	Policy:         capsule.TimeAndKey,
	NewPortableKey: true, // res.PortableKey is the .dkk; encode it with accesskey.Encode
	Comment:        "For Ana",
	Now:            time.Now,
})

// Inspect: steps 1–8, no network, no secrets.
in, err := capsule.Inspect(f, capsule.InspectOptions{Registry: reg})

// Open: steps 1–18; the release is verified locally. A format 3 capsule
// gives its files to a Sink, which publishes them in Commit, at step 18.
opened, err := capsule.Open(ctx, nil, f, capsule.OpenOptions{
	Registry:  reg,
	Source:    drand.New(),
	AccessKey: key, // or Identities: []age.Identity{...}
	Sink:      sink,
	Now:       time.Now,
})
if errors.Is(err, datekeys.ErrReleaseUnavailable) { /* not yet */ }
```

A `Sink` gets `Begin` with the head, `Create` for each file and `Commit` only
when step 17 has passed; after any failure it gets `Abort`, and nothing it
received may be presented as valid (spec §56). `opened.Head` holds the paths,
sizes, SHA-256 and modification times, the comment and the declared author,
and `opened.Verdicts.Lines()` the verdicts to show before them (spec §29.7).
`Open` without a `Sink` stops right after step 2 with `capsule.ErrSinkRequired`,
a caller error with no code. Capsules of formats 1 and 2 still stream their
content to `dst`, never the padding. `opened.Format` is the format of the
capsule: format 1 hides neither the number of credentials nor the exact
length of the content, so show it (spec §70). Every protocol failure wraps
one of the 18 normative errors of spec §69, so `errors.Is` and
`datekeys.Code(err)` identify it.

## Security properties and limits

- **Time confidentiality** holds under drand's threshold assumption. The
  Quicknet timelock is **not post-quantum**: ciphertexts kept for years are
  exposed to harvest-now, decrypt-later (spec §7.7, §53).
- **No trust in servers**: the profile is pinned in the binary, the round is
  computed locally, releases are BLS-verified locally, and a valid signature of
  another round is rejected (spec §13, §17, §51).
- **Integrity**: framing, header, control and payload are authenticated
  against whoever does not know the file keys: a third party's change makes
  opening fail (fixtures and the mutation corpus). Once the round is
  published anyone can compute the time file key, and anyone can seal a new
  control for a public header; who can write each part, and from which step
  it is bound, is the trust model of spec §27 and §55.1.
- **Metadata privacy**: until the date, the exact length of the content, the
  number of credentials, and the names, sizes and number of the files stay
  hidden, beyond what the padded size P bounds; the date, the access policy,
  `capsule_id` and the header extensions do not (spec §55.2).
- **Safe extraction**: the paths of a head cannot leave the folder, collide
  on Windows, macOS or Linux, hide characters or change the direction of the
  text; the rules use fixed Unicode 18.0.0 tables, never those of the
  platform (spec §29.5, §29.6).
- **No authorship**: the declared author and the comment are text of the
  creator that proves nothing, and this version checks no signature and no
  seal: its verdicts only say so, and never decide the opening (spec §29.3,
  §29.7, §36.1). `time_and_key` adds an access barrier, not a signature.
- **Recovery years later** needs the historical release: from a drand relay
  that still serves it or from any cache, re-verified locally (spec §50).

See [SECURITY.md](SECURITY.md).

## Conformance and tests

```bash
go test ./...                               # unit, golden vectors, fixtures, mutation corpus
go test -race -cover ./...
go test -fuzz=FuzzInspect ./capsule         # one fuzz target at a time
go test -tags interop ./capsule             # official age and tle CLIs open our files
go test -tags integration ./capsule ./provider/drand   # live Quicknet
```

- `testdata/vectors`: profile hash, date→round and `dk1_` vectors (spec §65, §66),
  CBOR profile and schema vectors, padding vectors (spec §29.1), the paths, the
  keys of R7, the heads and the security areas of format 3 (spec §67), the
  exported mutation corpus and a differential corpus of the pre-unlock checks;
  formats in [`testdata/README.md`](testdata/README.md).
- `testdata/fixtures`: official `.dkc`/`.dkk` fixtures over published rounds,
  with the BLS signature embedded and every intermediate value (spec §67, §68);
  they decrypt offline. Nine are of format 3; the seven of format 2, from
  v0.9, and the five of format 1, from v0.8.2, are kept for compatibility.
  Each `.dkc` has its frozen `datekeys inspect -json` output.
- `internal/testkit.Mutations`: the mutations of spec §64, the 33 of its first
  two lists in each format, the 23 of the list of format 2 and the 47 of the
  list of format 3, and 40 more, each with its exact error and step, or its
  verdicts when it opens, and a check that pre-unlock failures never cause a
  release request; exported to `testdata/vectors/mutations.json`.
- [`docs/traceability.md`](docs/traceability.md): spec section → code → test.
- [`spec/datekeys.cddl`](spec/datekeys.cddl): CBOR schemas.

## License

Code: Apache-2.0 ([LICENSE](LICENSE)). Specification: CC-BY-4.0
([spec/README.md](spec/README.md)). `codec/bech32` is copied from age under its
own license. "DateKeys" is a reserved name: see [TRADEMARKS.md](TRADEMARKS.md).