Why Blockchain Matters for Evidence
A SHA-256 hash proves that a file hasn't been altered — but it doesn't prove when it was created. Anyone could hash a file today and claim it was created last year.
Blockchain anchoring solves this by writing the hash to a public, immutable ledger with a timestamp that cannot be retroactively changed. Once a hash is recorded on the blockchain, its existence at that specific point in time is permanently verifiable by anyone.
TrueSnap uses the Polygon blockchain for this purpose — a widely adopted, energy-efficient network with transaction records accessible through Polygonscan.
What You Need
- The transaction hash (TX hash) from your evidence package (found in the forensic certificate or metadata.json)
- A web browser
- Optionally, the SHA-256 hash of your evidence package for cross-verification
Step-by-Step: Looking Up Your Evidence
Step 1: Open Polygonscan
Navigate to https://polygonscan.com in your browser. No account or login is required — Polygonscan is a free, public blockchain explorer.
Step 2: Enter Your Transaction Hash
Find the search bar at the top of the page. Paste your transaction hash (TX hash), which looks something like:
0x7a8b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b
Press Enter or click the search icon.
Step 3: Read the Transaction Details
You'll see a detailed transaction page with several fields. Here's what each one means:
Understanding the Transaction Fields
Transaction Hash
The unique identifier for this specific blockchain transaction. Think of it as a receipt number — it permanently identifies this particular record.
Status
Should show Success. This confirms the transaction was properly recorded on the blockchain.
Block
The block number in which this transaction was included. Blocks are sequential and immutable — once confirmed, the data in a block cannot be changed.
Timestamp
The exact date and time the transaction was recorded on the blockchain. This is your proof of time — it establishes that the evidence hash existed no later than this moment.
Polygon blocks are produced approximately every 2 seconds, so timestamps are precise to within a few seconds.
From
The wallet address that submitted the transaction. For TrueSnap evidence, this is TrueSnap's anchoring service address.
To
The receiving address or contract. This may be a smart contract used for evidence anchoring.
Value
The amount of MATIC (Polygon's native currency) transferred. For hash anchoring, this is typically 0 MATIC since the purpose is data recording, not payment.
Input Data
This is the most important field for evidence verification. Click "Click to see More" or "View Input As" and select UTF-8 to see the decoded data.
The input data contains your SHA-256 evidence hash. This is the hash that was permanently recorded on the blockchain at the timestamp shown above.
Cross-Verifying Your Evidence
To complete the verification:
- Compute the SHA-256 hash of your evidence package on your own computer
- Compare it with the hash shown in the transaction's Input Data field
- Check the timestamp to confirm it aligns with your expected capture time
If the hashes match, you have mathematical proof that:
- Your evidence existed in its current, unmodified form at the blockchain timestamp
- No one has altered the evidence since it was captured
- The timestamp is trustworthy because it comes from a decentralized, public ledger
Why Polygon?
TrueSnap chose Polygon for several reasons:
- Public and decentralized — No single entity controls the network or can alter records
- Low transaction costs — Anchoring costs fractions of a cent, keeping evidence capture affordable
- Fast confirmation — Transactions confirm in seconds, not minutes
- Ethereum-compatible — Polygon is an Ethereum Layer 2 network, inheriting its security model
- Widely recognized — Polygonscan is a trusted, established blockchain explorer
Common Questions
Can a blockchain record be deleted or modified?
No. Once a transaction is confirmed and included in a block, it becomes part of the permanent blockchain history. Altering it would require rewriting the entire chain from that block forward — a computational impossibility on established networks.
What if Polygonscan goes offline?
Polygonscan is an explorer — a window into the blockchain — not the blockchain itself. If Polygonscan were unavailable, the same data could be accessed through any other Polygon node or explorer. The blockchain data exists independently of any single service.
Does this replace legal timestamp services?
Blockchain timestamps serve a similar function to trusted timestamp authorities (TSAs) but with added benefits: they are publicly auditable, don't depend on a single provider, and are permanently accessible. Courts in multiple jurisdictions have accepted blockchain timestamps as evidence of timing.
How much does blockchain anchoring add to the cost?
TrueSnap includes blockchain anchoring in every capture at no additional cost. The transaction fees on Polygon are negligible (typically less than $0.01).
Key Takeaway
Blockchain anchoring transforms a file hash from a static value into a time-stamped, publicly verifiable proof. By looking up your transaction on Polygonscan, you — or anyone else, including a court — can independently confirm exactly when your evidence was captured and that it remains unaltered. No trust in any single party is required.