A Roughtime protocol implementation in Go. Roughtime is a protocol for secure rough time synchronization, providing cryptographically signed timestamps with proof of server authenticity. This implementation covers Google-Roughtime and IETF drafts 01–19.
The protocol package implements the Roughtime wire format for both server and
client use. Ten wire format groups handle all version differences:
| Wire Group | Versions | Key Differences |
|---|---|---|
| Google-Roughtime | 64B nonce, SHA-512 (64B), Unix µs, no header | |
| Draft 01 | 01 | ROUGHTIM header, SHA-512/32B, MJD µs, 64B nonce, NONC in SREP |
| Draft 02 | 02 | SHA-512/256 (distinct algorithm), NONC in SREP |
| Draft 03 | 03, 04 | NONC moved to top-level response, SHA-512/32B |
| Draft 05 | 05, 06 | 32B nonce |
| Draft 07 | 07 | SHA-512/256, delegation context without trailing hyphens |
| Draft 08 | 08, 09 | Unix seconds, ZZZZ padding |
| Draft 10 | 10, 11 | SRV tag, RADI ≥ 3 |
| Draft 12 | 12, 13 | New delegation context, full-packet Merkle leaf, VERS in SREP |
| Draft 14 | 14, 15, 16, 17, 18, 19 | TYPE tag in request and response |
Version negotiation selects the highest mutually supported version. Drafts 12–19
share version number 0x8000000c on the wire; the TYPE tag in the request
distinguishes 12–13 from 14+.
ParseRequest auto-detects Google vs IETF framing and extracts request fields.
SelectVersion negotiates the best mutually supported version. NewCertificate
creates a signed online delegation certificate. CreateReplies builds signed
responses for a batch of requests.
CreateRequest builds a padded Roughtime request for any supported version.
VerifyReply authenticates the server's response: it verifies the delegation
certificate, the signed response signature, the Merkle proof, and validates that
the midpoint falls within the delegation window.
nonce, request, err := protocol.CreateRequest(
[]protocol.Version{protocol.VersionDraft12},
rand.Reader,
)
// ... send request over UDP, receive reply ...
midpoint, radius, err := protocol.VerifyReply(
[]protocol.Version{protocol.VersionDraft12},
reply, rootPublicKey, nonce, request,
)See client/main.go for a complete working example.
The root package is a UDP Roughtime server. It reads a hex-encoded Ed25519 root key seed from disk, generates online delegation certificates, and automatically refreshes them before expiry.
roughtime -root-key /path/to/seed.hex [-port 2002]
The server uses a fixed worker pool sized to the CPU count, a sync.Pool for
read buffers, and atomic certificate swaps for lock-free request handling.
Responses that would exceed the request size are dropped per the amplification
protection requirement. The server shuts down gracefully on SIGINT/SIGTERM,
draining in-flight requests before exiting.
The client command queries one or more Roughtime servers and prints
authenticated timestamps with clock drift. It supports single-server mode and
multi-server mode via a JSON server list. IETF servers receive all supported
versions in a single VER tag, letting the server pick the best match.
go run ./client -addr time.txryan.com:2002 -pubkey iBVjxg/1j7y1+kQUTBYdTabxCppesU/07D4PMDJk2WA=
go run ./client -servers ecosystem.json
The debug command probes a Roughtime server to discover its supported protocol
versions and prints a full diagnostic dump of the request, response, signatures,
and delegation certificate.
go run ./debug -addr time.txryan.com:2002 -pubkey iBVjxg/1j7y1+kQUTBYdTabxCppesU/07D4PMDJk2WA=
A public Roughtime server is available at time.txryan.com:2002. Additional
details can be found at time.txryan.com.
{
"name": "time.txryan.com",
"version": "IETF-Roughtime",
"publicKeyType": "ed25519",
"publicKey": "iBVjxg/1j7y1+kQUTBYdTabxCppesU/07D4PMDJk2WA=",
"addresses": [
{
"protocol": "udp",
"address": "time.txryan.com:2002"
}
]
}go test ./protocol/
go test -race ./protocol/
$ go run client/main.go -servers client/ecosystem.json
Cloudflare-Roughtime-2 draft-11 2026-04-06T05:54:04Z ±1s rtt=10ms drift=-317ms
time.txryan.com draft-12 2026-04-06T05:54:04Z ±3s rtt=47ms drift=-354ms
roughtime.se draft-12 2026-04-06T05:54:04Z ±1s rtt=144ms drift=-451ms
3/3 servers responded
$ go run debug/main.go -addr time.txryan.com:2002 -pubkey iBVjxg/1j7y1+kQUTBYdTabxCppesU/07D4PMDJk2WA=
=== Version Probe: time.txryan.com:2002 ===
draft-ietf-ntp-roughtime-12 OK
draft-ietf-ntp-roughtime-11 OK
draft-ietf-ntp-roughtime-10 OK
draft-ietf-ntp-roughtime-08 OK
draft-ietf-ntp-roughtime-07 OK
draft-ietf-ntp-roughtime-06 OK
draft-ietf-ntp-roughtime-05 OK
draft-ietf-ntp-roughtime-01 OK
Google-Roughtime OK
Supported versions: draft-12, draft-11, draft-10, draft-08, draft-07, draft-06, draft-05, draft-01, Google
Negotiated: draft-ietf-ntp-roughtime-12
=== Request ===
Size: 1024 bytes
00000000 52 4f 55 47 48 54 49 4d f4 03 00 00 04 00 00 00 |ROUGHTIM........|
00000010 04 00 00 00 24 00 00 00 28 00 00 00 56 45 52 00 |....$...(...VER.|
00000020 4e 4f 4e 43 54 59 50 45 5a 5a 5a 5a 0c 00 00 80 |NONCTYPEZZZZ....|
00000030 cf df 6a 2b 3c 7f 0d b3 f4 a9 4e 82 81 94 45 6d |..j+<.....N...Em|
00000040 7e 4f 25 67 e7 12 56 29 b4 bc 16 51 47 af 8a e7 |~O%g..V)...QG...|
00000050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
...
--- Request Tags ---
VER: 0c000080
NONC: cfdf6a2b3c7f0db3f4a94e828194456d7e4f2567e7125629b4bc165147af8ae7
TYPE: 00000000
ZZZZ: (940 bytes of padding)
=== Response ===
Size: 472 bytes
00000000 52 4f 55 47 48 54 49 4d cc 01 00 00 08 00 00 00 |ROUGHTIM........|
00000010 40 00 00 00 44 00 00 00 64 00 00 00 68 00 00 00 |@...D...d...h...|
00000020 68 00 00 00 f0 00 00 00 88 01 00 00 53 49 47 00 |h...........SIG.|
00000030 56 45 52 00 4e 4f 4e 43 54 59 50 45 50 41 54 48 |VER.NONCTYPEPATH|
00000040 53 52 45 50 43 45 52 54 49 4e 44 58 14 19 30 43 |SREPCERTINDX..0C|
00000050 c4 50 2e dd ab 83 58 6e 34 65 61 33 e4 66 42 18 |.P....Xn4ea3.fB.|
...
--- Response Tags ---
SIG: 14193043c4502edd...d205753d499b5df1d06c240b
VER: 0c000080
NONC: cfdf6a2b3c7f0db3f4a94e828194456d7e4f2567e7125629b4bc165147af8ae7
PATH: (empty)
SREP: (136 bytes)
CERT: (152 bytes)
INDX: 00000000
TYPE: 01000000
=== Verified Result ===
Round-trip time: 45.260875ms
Midpoint: 2026-04-06T05:54:08Z
Radius: 3s
Local time: 2026-04-06T05:54:09.320258Z
Clock drift: -1.32s
=== Response Details ===
Version: 0x8000000c (draft-ietf-ntp-roughtime-12)
Signature: 14193043c4502edd...d205753d499b5df1d06c240b
Nonce: cfdf6a2b3c7f0db3f4a94e828194456d7e4f2567e7125629b4bc165147af8ae7
Merkle index: 0
Merkle path: 0 node(s)
=== Signed Response (SREP) ===
Merkle root: 7ce214773d8658f45ebf06268b53eb669a365ae4c761198d5ec14fe3ec196672
Midpoint (raw): 1775454848 (2026-04-06T05:54:08Z)
Radius (raw): 3
VER in SREP: 0x8000000c (draft-ietf-ntp-roughtime-12)
VERS in SREP: draft-01, ..., draft-12
=== Certificate ===
Signature: d7c29a2d28346a15...a1d8d002
Online key: 94a5cd8e2cdabb62dbd92d760e8dd177a27a2e42fc7d068744358d52bac05ed8
Not before: 2026-03-30T05:53:29Z
Not after: 2026-05-18T05:53:29Z
Expires in: 1007h59m20s
Copyright (c) 2026 Tanner Ryan. All rights reserved. Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
