Cairn Note

Words can be written after the fact. A trusted timestamp can't. With generative AI, convincing text takes seconds to produce, so a record that turns up later is easy to doubt: "Was this really written back then, or just now?" File dates follow the device clock and can be changed, as can the dates in a notes app. Cairn Note solves this one problem. It keeps what you write in a form that lets others confirm, later, that it already existed at that date and time. ■ HOW IT WORKS When you save a record, the app calculates a "fingerprint" (a hash) of its contents. Change even one character and the fingerprint is completely different. Only this fingerprint goes to an independent timestamp authority, which returns a certificate that it existed at that date and time. The certificate is kept with your record. • The authority never receives your text, photos, audio, or attachments • If the contents change later, verification shows a mismatch (using Edit takes a new timestamp at the time of the edit) • Check it yourself anytime with View Certificate • Export records as a ZIP that can be verified with common tools, without trusting Cairn Note or its developer ■ NOT JUST TEXT Attached photos, audio, videos, and documents share one fingerprint with your text, so the record shows that on that date, this text and this photo both existed. • Swapping a photo or editing a recording later shows up as a mismatch • The number and order of attachments don't change the fingerprint • Tags, location, and creation date are not covered by the proof; the time that counts is the one the third party certified Timestamps follow RFC 3161 and come from FreeTSA. With Premium, Blockchain Timestamp also records the fingerprint on the Bitcoin blockchain via OpenTimestamps. ■ LOCKED ON YOUR DEVICE • Text and attachments are encrypted on your device (AES-256-GCM) • Only three ways in: your PIN, Face ID / Touch ID, or your recovery code. Someone who doesn't know your PIN can't read your records, even with your phone in hand • Your recovery code is your last-resort key if you switch devices or lose your phone. Neither the app nor the developer keeps a copy, so please write it down ■ FOR PEACE OF MIND • PIN or Face ID / Touch ID when the app opens, and Auto-Lock • Block Screenshots • Camouflage Screen: a double-tap switches to what looks like an ordinary notes app • Notification Text (Camouflage): choose what reminders say, such as "Time to drink water" ■ AN EVERYDAY JOURNAL • Text, photos, and documents, plus audio and video recording (Premium) • Events tags (Work, Health, Money...) and Feelings tags (Happy, Calm, Grateful...), in the order you choose • Keyword search, tag filters, and Fuzzy search, all on your device • Look back by day in Calendar, or browse by year, month, and day • Three text sizes, and a Green, Pink, or Dark theme • Drafts save automatically every few seconds ■ FREE • Up to 5 timestamped records a day, attachments included • Photo and document attachments, tags, search, and Calendar • All the security and privacy features above • ZIP export and import ■ CAIRN NOTE PREMIUM (ONE-TIME PURCHASE) • Unlimited records • Edit records • An additional timestamp on the Bitcoin blockchain (OpenTimestamps) • Encrypted backup to iCloud Drive, and restore • Audio recording (no time limit) and video recording (up to 5 minutes) • Location recording (stored encrypted; never sent to the developer) • Add and hide tags Try Premium free for 14 days after you first open the app. Premium is a one-time purchase, not a subscription, with no further charges after that single payment. ■ PLEASE NOTE Cairn Note can prove only two things: that a record with this content existed at that date and time, and that it hasn't been changed since. It can't prove that what's written is true, or who wrote it. It doesn't guarantee that your records have any legal effect. When it matters, please talk to a professional.