Crate roughtime 

A no_std-capable client for the Roughtime secure time synchronization protocol.

Roughtime lets a client obtain the current time from a set of untrusted servers while being able to cryptographically prove, after the fact, that any server which lied about the time can be caught (via Ed25519 signatures over a Merkle tree of recent requests). This crate implements the client side only: building requests, parsing and verifying responses, and (optionally) querying real servers over the network.

Feature flags

Exactly one crypto backend feature must be enabled:

• rustcrypto — pure-Rust [ed25519-dalek] + [sha2], no_std-capable.
• aws-lc-rs — [aws-lc-rs], the default.
• aws-lc-rs-fips — aws-lc-rs built in FIPS mode.

Layered on top:

• std (default) — enables the networking clients and the Linux os-clock backend.
• tokio-client (default) — an async, concurrent multi-server query client.
• blocking-client — a synchronous std::net::UdpSocket-based client.
• os-clock — an opt-in Linux SystemClock implementation that can set the OS wall clock forward to the verified time floor.
• dnscrypt (default) — resolves well-known Roughtime server hostnames via dnscrypt, an authenticated, encrypted DNS transport, instead of the OS’s plaintext, unauthenticated resolver. This closes the one remaining plaintext, unauthenticated hop in an otherwise end-to-end-verified time-sync flow, and means callers no longer have to resolve/pin server IPs by hand. See resolve::resolve_servers/resolve::resolve_servers_async and client::TokioClient::query_well_known/[client::BlockingClient::query_well_known].
• build-time-floor — opt-in, not in default. Ratchets the anti-rollback floor forward to the build day using the build machine’s wall clock. Leave this disabled for reproducible builds (e.g. attested boot images); see floor for details.

A no_std consumer (e.g. a kernel or bootloader) should build with --no-default-features --features rustcrypto to get the wire-format, request-building, and response-verification primitives with no networking or OS dependency — supplying its own I/O and randomness.

Requirement: a global allocator

This crate always uses alloc (for Vec-backed message parsing), even in no_std builds. no_std consumers must provide a global allocator.

Security posture

This is a client-only crate: it never holds Ed25519 private key material, only verifies server-supplied public keys and signatures. The one client-generated secret-like value is the 64-byte nonce, which is zeroized on drop (see request::Nonce). Raw response bytes and extracted public keys are intentionally not zeroized — they are bulk public-protocol data, and scrubbing them would cost real performance for no confidentiality benefit.

Re-exports

pub use error::Error;

pub use request::Nonce;

pub use request::build_request;

pub use servers::ROUGHTIME_SERVERS;

pub use servers::RoughtimeServer;

pub use verify::VerifiedTime;

pub use verify::verify_response;

pub use resolve::resolve_servers;

pub use resolve::resolve_servers_async;

Modules

client

Shared networking-client types: configuration and multi-server consensus logic.

clock

The SystemClock abstraction over reading/setting a system wall clock.

date

A minimal, dependency-free RFC 1123-ish HTTP date parser.

error

The crate’s structured error type.

floor

The anti-rollback time floor.

request

Building Roughtime request messages.

resolve

Secure Roughtime-server hostname resolution via dnscrypt.

servers

The set of well-known public Roughtime servers.

tags

Roughtime wire-format tag constants.

verify

Verification of Roughtime responses: signature checks, Merkle inclusion proof, and the anti-rollback floor.

wire

Parsing of the Roughtime wire format: a flat tag-length-value message encoding.