Cryptographic work proof: tamper-evident field records.
Cryptographic work proof is WorkTrac's tamper-evident record system for field crews. Every clock-in, GPS coordinate, photo, task completion, and safety incident is cryptographically signed at the moment it is captured on the device, then chained to the preceding record so any later edit, deletion, or backfill breaks the chain and is visible on audit. The result is a defensible evidence trail that holds up under prevailing-wage audits, billing disputes, OSHA inspections, insurance claims, and DOL investigations — the same arguments where field service contractors routinely lose money to "your word against theirs." Cryptographic work proof is included in every WorkTrac tier, including Starter at $29/mo, and the chain extends across the offline-first sync architecture so events captured in dead zones carry the same signature as events captured online. The verification key is published; auditors can inspect the chain without contacting WorkTrac.
What cryptographic work proof actually does
The phrase "tamper-evident" is doing real work here. Most field service tools store records in a database that the vendor — and any admin with the right credentials — can quietly edit. A clock-in time, a GPS coordinate, a safety incident severity, a timesheet approval can all be changed weeks later with no record of the change. That is the failure mode that loses contractors prevailing-wage audits, costs them dispute resolutions, and creates problems on the witness stand in a workers' comp dispute.
WorkTrac signs each captured event on the device using a per-org private key, includes a reference to the previous event in the org's chain, and stores the signature alongside the record. The server validates each signature on ingest and rejects events whose signatures do not match. After the fact, anyone with the org's public key can replay the chain and detect a tampered record by the broken signature link — without needing access to the underlying database and without needing WorkTrac's cooperation.
The result is a record that is honest about its own integrity. A clean chain says "every event in this period is exactly what the device captured." A broken link says "something was changed, here is which record, here is when." That single property converts a contractor's evidence file from "your word" to "checkable."
What gets signed in the chain
The chain covers every capture event the mobile app generates plus the timesheet-approval events the dashboard generates. Adding optional metadata to a record (a manager note, a category change) is also captured as a chain event rather than a silent in-place edit, so the audit history shows who annotated what and when.
GPS coordinates, accuracy radius, device timestamp, matched geofence ID — all signed.
Required-photo evidence, completion timestamp, completing user, attached comments.
Photo hash + EXIF + capturing user + parent task or incident.
Full incident report including severity, witnesses, root cause, and corrective action.
Emergency events with GPS and triggering user. Critical for liability defense.
Approving user, approved set of shifts, approval timestamp. Manager edits show in the chain.
Where work proof pays off
Prevailing-wage and certified-payroll audits are the canonical use case. A DOL investigator asks for the on-site hours for a Davis-Bacon project; the contractor produces the signed chain for the period; the investigator runs verification against the published public key and confirms no records were edited. The audit closes without a finding. The contractor who can't produce this often ends up paying back wages and penalties even when their actual records are accurate — because they cannot prove they didn't edit them.
Billing disputes resolve faster. A client says "your crew wasn't on-site Thursday" — the contractor pulls the signed GPS punches and photos for Thursday, runs verification, and the dispute closes on physical evidence rather than email arguments. Workers' comp claims and OSHA inspections work the same way: the contractor produces the safety-incident record signed at the moment of capture, which the insurer or inspector can verify did not have its severity or root-cause field edited after the fact.
And on the inside-the-business side, work proof neutralizes the small-but-frequent damage from quiet record-edits — a foreman softening a near-miss severity to avoid a conversation, an office admin shifting an inconvenient clock-in by ten minutes. The chain does not prevent these edits; it makes them visible so the company can decide how to handle them.
How verification actually works
Each org has a public verification key surfaced in the dashboard's audit trail view. The org's admin can export a signed event log for any time window — typically a payroll period, a job, or a DOL request — as a JSON file plus the public key. An auditor or third party runs the verification: parse the events in order, recompute each event's expected signature using the public key and the previous event's signature, and confirm every link matches. The verifier code is independent of WorkTrac; an auditor can build it from the published spec or run the open verifier WorkTrac provides. No login, no API key, no vendor cooperation. The whole point of the design is that the records remain checkable even if the contractor loses access to WorkTrac.
Common questions, answered.
It is WorkTrac's tamper-evident record system. Every clock-in, GPS coordinate, photo, task completion, and safety incident is cryptographically signed on the device at capture and chained to the previous record. After-the-fact edits break the chain and are visible to anyone with the org's public verification key.
Also explore
GPS punches signed at capture inherit the same tamper-evidence as the chain itself.
Records captured in dead zones get the same signature as online events. The chain survives offline gaps.
OSHA incident reports inherit the chain. Inspector-ready records that cannot be edited silently.
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