Seal a document, with a deadline on it

Some documents should not be readable forever. A draft sent for comment, a valuation, a set of accounts shared with one bidder: each of them has a date after which nobody sensible wants a copy still floating about. This seals the file under AES-256 with a key stretched from your password, and writes a deadline into it that GoSmart PDF honours. Know what you get back before you start: not a password-protected PDF, but a .gspkg container, which Acrobat, Preview and every other PDF reader refuse to open at all — whoever you send it to opens it on this page, or in the GoSmart PDF app for Mac. Be clear too about which half is doing the work: the encryption is the protection, and it is strong. The deadline is an instruction to software, checked against the reader's own clock, and anybody holding the file and the password can keep the document by opening it before the date. Nothing here deletes a file on somebody else's machine, because no web page can. Every file is opened, changed and saved by your own browser. Nothing is uploaded to a server, nothing is stored, and no account is needed.

• AES-256-GCM, with the key stretched from your password by PBKDF2 at 600,000 rounds, which is OWASP's current figure
• A deadline of an hour, a day, three days, a week, a month or ninety days
• The output is a .gspkg container and not a PDF, so no PDF reader opens it and the recipient needs this page
• The same .gspkg the GoSmart PDF Mac app writes, so a container opens in either
• The document's own name is sealed with it, so an intercepted container does not say what it is
• The recipient opens it on this page — no account, no install, nothing uploaded
• What the deadline is and is not is spelled out on the tool, not buried in a footnote
• No password recovery, because there is no copy of the password to recover it from

Support and billing: support@gosmartpdf.com. Operated by Mrityunjay Kumar, India. Payments by Dodo Payments, our merchant of record.

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