How CaseStamp Works
CaseStamp doesn't invent its own security or location methods. Every technical element is built on published, internationally recognized standards, computed by the device's own built-in system libraries. This page documents what each one is and where it comes from, so a skeptical user, a lawyer, or any other professional can verify the app's methods rest on recognized standards, not proprietary claims.
File integrity — SHA-256
What it does: produces a unique 64-character fingerprint of each photo or video the moment it's saved. If even one byte of the file is later altered, the fingerprint changes completely, so any tampering is detectable.
Standard: SHA-256 is part of the SHA-2 family, published by the U.S. National Institute of Standards and Technology (NIST) in federal standard FIPS 180-4. It is a public standard, used worldwide in banking, government, and security.
How CaseStamp uses it: the hash is computed on-device using the platform's built-in Web Crypto API, provided by the system WebView. CaseStamp does not implement its own cryptography.
Location — GPS / WGS 84
What it does: tags each entry with the coordinates where it was captured, plus an accuracy value (e.g. ±5m) showing how precise the fix was.
Standard: coordinates come from the Global Positioning System (GPS) and are expressed in the WGS 84 world reference datum. CaseStamp requests a location fix at the moment of capture. To keep capture fast, the device may return a fix it obtained within the previous 30 seconds rather than waiting for a new one — so a stamped location reflects where the device was at capture time, within that window. It never falls back to an older or estimated position.
Offline: GPS is satellite-based and works without a network connection, though a fix may take longer offline. If no location can be obtained, the entry still saves and is marked "location unavailable" — CaseStamp never substitutes an old or approximate location.
How CaseStamp uses it: location comes from the device's native location services; CaseStamp reads the result, it does not estimate position itself.
Time — ISO 8601
What it does: stamps each entry with the date and time it was saved. The timestamp is set at save time and can't be changed within the app.
Standard: timestamps are recorded in ISO 8601 format, the international standard for representing dates and times. ISO 8601 governs how the time is written, not where it comes from — the time itself is read from your device's clock at the moment of capture.
The report — PDF
What it does: exports a case as a form-style report document.
Standard: PDF is an open international standard (ISO 32000), readable on virtually any device.
How to verify a report
Because these are open, published standards implemented by the device's own built-in libraries, anyone receiving a CaseStamp report can independently verify a file: compute its hash with any standard tool and compare it character-for-character to the SHA-256 value printed in the report.
To verify a file yourself:
- On Mac or Linux: open Terminal and run
shasum -a 256 filename - On Windows (Command Prompt): run
certutil -hashfile filename SHA256 - On Windows (PowerShell): run
Get-FileHash filename -Algorithm SHA256
If the file is unaltered, the result will exactly match the SHA-256 hash printed in the report for that entry. If even one byte has changed, the hashes won't match. Some tools print the hash in uppercase or with spaces between characters — ignore case and spacing when comparing.
Example (placeholder data, not a real case):
Suppose a report lists this hash for a video —
c54bae9222ab83f222442b8ceec82ed35985f2be14bb5ce411601f425d7b2a32
You run:
shasum -a 256 entry-004.mp4
and get back:
c54bae9222ab83f222442b8ceec82ed35985f2be14bb5ce411601f425d7b2a32
The two strings match exactly, so the file is unaltered. If even one character differed, the file would have been changed since it was recorded.
What tamper-evidence means — and doesn't
CaseStamp proves one thing precisely: that a photo or video hasn't been altered since you saved it. Each file gets a SHA-256 fingerprint the moment it's captured. If even one byte changes afterward, the fingerprint no longer matches — and anyone can check that with a standard tool.
What no documentation app can do — including this one — is prove that what's in a photo is true. A timestamp and fingerprint record when you saved a file and confirm that it hasn't changed since. They can't confirm the story behind it. Honesty about that limit is part of building a record that holds up.
CaseStamp does its part completely offline. Each entry is timestamped the instant you save it, with no network and no server involved — files leave your device only when you choose to send them.
CaseStamp is a documentation tool and does not guarantee any record will be accepted as evidence in a proceeding; admissibility is determined by applicable law.
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