Imagine this scenario: you send a financial report to a client on March 1st. Two weeks later, the client claims the figures in the report differ from the version they originally received. Who is telling the truth?
Without the right system in place, this question cannot be answered objectively. Emails can be edited, file metadata can be spoofed, and operating system modification timestamps can be altered by anyone within seconds. Proof of Existence solves this problem — in a way that relies on no one's authority or goodwill.
Proof of Existence is a technique that enables someone to prove that a file existed at a specific point in time and has never been altered since — without ever revealing the contents of the file to anyone. The final authority is mathematics itself.
The Problem It Solves
File metadata — including the "created date" and "modified date" visible in Windows Explorer or macOS Finder — can be changed by anyone. This is not a security flaw; it is simply how operating systems work.
File modification dates, email timestamps, and document metadata are not proof of integrity. All of them can be manipulated without leaving any trace detectable by standard tools.
Proof of Existence replaces trust in metadata with trust in mathematics. Instead of asking "when was this file last modified?" the system asks "does this file's mathematical fingerprint match the record stored on the ledger?"
How It Works: SHA-256 Hashes as Digital Fingerprints
At the core of Proof of Existence is the cryptographic hash function. VerixID utilizes SHA-256 — the same standard relied upon by global banking systems, governments, and internet infrastructure.
An SHA-256 hash possesses three mathematical properties that make it ideal as a file fingerprint:
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Deterministic The exact same file always yields an identical hash — on any computer, at any time, by anyone. No external variables affect the output.
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Avalanche Effect The slightest change — a single character, one pixel, one byte — results in a completely different hash. There is no pattern or correlation between minor edits and the resulting hash output.
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One-Way / Irreversible It is mathematically impossible to reconstruct the original file from its hash. This is what makes Zero-Custody technically possible: the system stores hashes without ever being able to "read back" the file contents.
Below is an illustration of how changing a single character results in an entirely distinct hash:
The two hashes above bear no resemblance to each other — despite a difference of only one character in the file. Tampering of any scale cannot be concealed.
Immutable Ledger: Recording to Prevent Repudiation
Calculating a hash alone is not enough. The hash must be recorded in an environment that cannot be tampered with alongside a trustworthy timestamp.
VerixID uses a PostgreSQL-based immutable ledger built with an append-only architecture: once data enters, there is no mechanism to alter or delete it — even by VerixID itself. Each entry logs the hash, the UTC timestamp, a unique Record ID, and request technical metadata.
VerixID's immutable ledger is architected with a 1-year retention policy*. There is no deletion mechanism. This is not a policy subject to change — it is an architecture structurally devoid of a DELETE function.
How to Prove a File Has Never Been Altered
The verification workflow is streamlined and can be executed independently by anyone — including auditors, legal counsel, or third parties involved in a dispute:
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Compute the hash of the file you want to verify Run an SHA-256 tool locally on your computer — available natively across all modern operating systems. Your file never needs to be uploaded anywhere.
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Compare it against the hash registered on the ledger Input the hash or Record ID into VerixID's verification interface. The system returns the ledger data: the registered hash, timestamp, and record status.
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Read the outcome Matching hash → the file has never been altered since the registration date. Mismatching hash → modifications occurred subsequent to registration.
Zero-Custody: Your Files Never Leave Your Device
The primary concern when utilizing document verification services is: "Are my files being saved on their servers?" VerixID answers this question not with promises — but with architecture.
The hashing process occurs entirely within the user's local device. Because hashes are one-way, it is structurally impossible to reconstruct the original file from the stored hash. This aligns seamlessly with data privacy mandates: no personal data or file content is ever stored on VerixID systems.
Four Properties That Make Proof of Existence Trustworthy
Comparison with Other Methods
| Method | Tamper-Proof? | Independent Verification? | 1-Year Retention? |
|---|---|---|---|
| File metadata (OS) | Yes, easily | No | No |
| Email timestamps | Yes, headers can be spoofed | Server-dependent | Not guaranteed |
| Conventional notarization | No, but slow and costly | Yes | Yes |
| Proof of Existence (VerixID) | No — mathematical | Yes — public, account-free | Yes — 1-year retention |
Register Your File's Digital Fingerprint
Files never leave your device. Only hashes are recorded — permanent, verified, for 1 year*.
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