Use Case
Blockchain Timestamps for Forensic Engineers
Tamper-evident chain of custody for field data. How forensic engineers across structural, accident, fire, product-failure, and environmental disciplines use SHA-256 blockchain anchoring to establish defensible digital evidence.
The chain-of-custody problem in forensic practice
A forensic engineer's report is only as defensible as the data it relies on. When that data is digital — photographs, drone imagery, LIDAR scans, sensor logs, video walkthroughs — the chain of custody question becomes: how do you prove the file presented to the court is the same file collected at the scene, with no intervening modification?
Traditional answers involve write-protected memory cards, custodial logs, witnessed transfer protocols, and forensic image acquisition. These work, but they're operationally heavy and depend on every link in the procedural chain being intact. A single break — a custodian who can't testify, a transfer log entry that's ambiguous, a date that doesn't match — can undermine the evidence regardless of whether tampering actually occurred.
A blockchain-anchored hash addresses the integrity question directly. At the moment a file is collected, its SHA-256 hash is anchored on-chain. Any subsequent modification — accidental or intentional — produces a different hash, and the mismatch is mathematically detectable. The chain of custody from that moment forward is verified by cryptography, not procedure.
Practical workflow for forensic disciplines
Structural and civil forensics
Post-collapse, post-failure, or post-event site documentation. Anchor photographs, drone orthoimagery, 3D scan files, and survey data at the moment of capture. The on-chain timestamp documents not only the date but the integrity of the captured state — critical for analyses that may proceed for months or years before trial.
Accident reconstruction
Scene photographs, total-station survey data, LIDAR point clouds, vehicle inspection imagery, and event data recorder (EDR) downloads. Anchor each file as it's collected. The anchored set documents the scene's exact state at the moment of inspection, defending against later challenges that the scene was modified, contaminated, or selectively photographed.
Fire and arson investigation
Origin and cause determination depends on photographic and physical documentation of burn patterns, evidence collection, and scene conditions. Anchor the photo set, sample collection logs, and scene reports. The chain of timestamps documents the investigator's work product from initial response through final report.
Product failure analysis
Component photography, microscope imagery, CT scan data, testing protocols, and laboratory measurements. Anchor each at the point of generation. For products with potential class-action implications, the early anchoring establishes the investigator's findings before any pressure to alter the analysis exists.
Environmental forensics
Site condition documentation, contamination evidence, sampling logs, and chain-of-custody for laboratory samples. Anchor field documentation as it's generated. For long-running environmental cases that may take years to resolve, the anchored record proves what conditions existed at each documented site visit.
Field workflow considerations
- Connectivity: SHA-256 hashing is purely local and works offline. Anchoring to the blockchain requires connectivity, but can be deferred. A field engineer can compute hashes at the scene, queue them, and anchor when back at the office. The file's hash doesn't change — what gets recorded is when the anchor was created.
- Large files: Hash size is fixed at 64 hexadecimal characters regardless of file size. A 200 GB LIDAR dataset hashes to the same length as a 200 KB JPEG. File content is never transmitted — only the hash.
- Mobile capture: Phones, tablets, and field laptops can all compute SHA-256 locally and call the ProofLedger API. Field-friendly workflows can be automated with the REST API on the Formal Legal / Compliance tier.
Expert witness deposition and trial
When an expert witness is asked at deposition whether the files presented are the same files collected at the scene, the anchored hash gives a deterministic answer: hash the file in question, compare to the on-chain record, and the result is either match or mismatch. The expert is not relying on memory, custodial logs, or third-party assurances — they're relying on a mathematical comparison anyone can perform.
The verification is adversarial by design. Opposing counsel can run pip install verify-proof on their own machine and independently confirm the timestamp against the public blockchain. ProofLedger's cooperation is not required.
What ProofLedger sees
Nothing. The SHA-256 hash is computed in the browser or via the API client before any network transmission. ProofLedger receives only the 64-character hex hash, which mathematically cannot be reverse-engineered to reconstruct the original file. Privileged materials, sealed evidence, and confidential client work can be anchored without content disclosure risk.
Pricing
Baseline (free, 5 lifetime proofs) for evaluation. Standard Evidence ($9.99/month, 100 proofs) for individual practitioners. Elevated Evidence ($49.99/month, high-volume) for active firms. Formal Legal / Compliance ($99.99/month, unlimited + API) for firms with integrated field-capture workflows. Full pricing →