1
Hash locally i
Your browser computes SHA-256 from the exact file bytes before anything is sent.
2
Only the hash is sent i
The proxy forwards the 32-byte digest to CertiSigma; the file, filename and metadata stay local.
3
Download the PDF proof i
T0 is immediate; T1 eIDAS timestamp and T2 Bitcoin anchor can later strengthen the same record.
Independent checks:
bundle integrity audit
and
T1 inclusion proof audit .
Step 1 · Local hashing
Hash locally
The browser reads the selected file bytes and computes SHA-256 locally.
The original content is never uploaded.
Any byte-level change produces a different digest.
This proves byte integrity, not authorship, ownership or copyright.
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Step 2 · Hash-only boundary
Only the hash is sent
The same-origin proxy forwards only the 32-byte SHA-256 digest to CertiSigma for attestation. File contents, filenames, previews and metadata remain local to your browser and PDF.
The CertiSigma API signs and timestamps the digest, not readable content.
The public proof identifies the digest and attestation ID.
Short or predictable inputs can still be guessed from their hash; do not use hashing as secrecy.
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Step 3 · User-owned receipt
Download the PDF proof
The PDF is the human-readable receipt to keep with the original file. It contains the digest, attestation ID, T0 signature context and verification instructions.
T0 is immediate ECDSA evidence over the digest.
T1 and T2 can later strengthen the same record with qualified timestamp and Bitcoin/OpenTimestamps evidence.
Verification recomputes the hash from the original content and compares it with the attested digest.
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Your content never leaves your device. The browser computes SHA-256 locally and sends only the 32-byte hash through a server-side proxy. No upload, no account, no login.
ExistBefore creates cryptographic proof that your content existed at a specific time — before approval, before registration, before publication. You get an immediate ECDSA signature (T0), followed by a qualified eIDAS timestamp (T1) and a Bitcoin anchor (T2).
It does not prove authorship or ownership. It proves a fact: this specific sequence of bytes existed at this moment.
Works with any digital content
Brand names
Logo previews
Creative mockups
Fashion prototypes
Campaign visuals
Contracts & NDAs
AI prompts
Photographs
Audio & video
PDF documents
Code & designs
Any file
When you need a proof of existence