PDF Document
Drop your PDF here
Text-based · Scanned · Any size
Ownership Details
Owner Name optional
Date optional
Note optional
Sealed PDF
Drop the sealed PDF
The one with an embedded SUGANDH seal
A flower is remembered by its fragrance.
A document should carry the fragrance of its creator — invisible, but undeniable.
SUGANDH seals any PDF with a cryptographic fingerprint — invisible to the eye, impossible to fake, publicly verifiable by anyone. No account. No server. No secret phrase. Just math and Bitcoin.
What SUGANDH proves
1. This exact PDF existed before a specific Bitcoin block.
The seal is tied to a real Bitcoin block height fetched at the moment of sealing. That block was mined at a known point in time — publicly verifiable on any block explorer forever.
2. It has not been modified since sealing.
Every page gets its own SHA-256 fingerprint. Any change — even a single character — is caught and shown exactly which page was affected.
3. It belonged to a named owner.
Owner name, date, and note are woven into the seal and readable by anyone who verifies.
The seal is tied to a real Bitcoin block height fetched at the moment of sealing. That block was mined at a known point in time — publicly verifiable on any block explorer forever.
2. It has not been modified since sealing.
Every page gets its own SHA-256 fingerprint. Any change — even a single character — is caught and shown exactly which page was affected.
3. It belonged to a named owner.
Owner name, date, and note are woven into the seal and readable by anyone who verifies.
The Algorithm
# Step 1 — fingerprint every page PageHash[i] = SHA-256( page_text ) # or pixel data if scanned # Step 2 — random salt (prevents backdating) Salt = crypto.getRandomValues( 32 bytes ) # Step 3 — base seal SealHash = SHA-256( PageHashes + Salt + Owner + Date ) # Step 4 — fetch current Bitcoin block (read-only API) blockHeight = GET blockstream.info/api/blocks/tip/height blockTime = GET blockstream.info/api/block-height/{blockHeight} # Step 5 — final hash ties document to Bitcoin block FinalHash = SHA-256( SealHash + blockHeight ) # Step 6 — short public ID DocID = FinalHash[ 0 : 8 ].toUpperCase()
Why Bitcoin block height?
A Bitcoin block is mined roughly every 10 minutes and its timestamp is immutable — no one can alter it. By embedding the block height into the FinalHash, your seal becomes mathematically tied to that moment in time. Anyone can verify: go to any block explorer, look up that block height, see the exact date and time it was mined. No trust in SUGANDH needed.
Why Salt?
Salt is random and stored inside the sealed PDF. Even if someone knows your owner name, date, and note — they cannot recreate the same SealHash because the original random salt existed only at that moment of sealing. Backdating is mathematically impossible.
Per-page analysis
Every page is hashed independently. During verification, each page is checked individually. For text-based pages, a word-overlap similarity score is also shown — so you know if a page had a minor edit or was completely rewritten. Scanned pages use pixel-level comparison.
Privacy
Everything runs in your browser. Your PDF never leaves your device. Only two tiny read-only API calls go out — to fetch the current Bitcoin block height and its timestamp. No document bytes. No upload. No account. The seal is embedded directly into the file you download.