Overview
Csign is a private document-signing tool that lets people sign and certify agreements without anyone, not even Csign itself, being able to read the contents. You upload a file, it is scrambled in your browser before it leaves your computer, and only the people you invite to sign get the code to unscramble it. A short fingerprint of the agreement (a one-way code that changes if the file changes) is then stored on a public blockchain, so anyone can later confirm the document is authentic and unchanged1.
Csign comes from Good Future, LLC, a small team that previously co-authored a developer handbook for Hyperledger Identus, the identity framework Csign is built on2. The product runs on Cardano, with a marketing page at csign.io and the actual web app behind a login at app.csign.io1. Csign sits in the broader signing and verification space on Cardano alongside other agreement and credential tools.
Key Features
- Documents stay private from Csign. Files are scrambled on the signer's device before they leave the browser, so the platform itself never sees the content of the agreement1.
- Public proof without public exposure. Each agreement gets a one-way fingerprint that is recorded on the Cardano blockchain, letting anyone confirm the document later without seeing what it says1.
- Direct key sharing between signers. The codes needed to unscramble a document move directly between signers using a private messaging standard, rather than passing through Csign's servers1.
- Built on a recognised identity framework. Csign uses Hyperledger Identus, formerly known as Atala PRISM, an open project now hosted by LF Decentralized Trust that lets people control their own digital credentials without a central provider2.
- Catalyst-funded research lineage. The founding team received a Cardano Catalyst grant for an Identus developer handbook and has submitted two further proposals to extend Csign itself34.
What to Expect
Visitors landing on csign.io see a single marketing page with a sign-up form for the mailing list and a button that opens the actual product in a new tab. Most of the experience lives inside the web app, which requires an account. A public demo is available for people who want to see the flow without signing up.
The product is positioned for two audiences. Individuals can use Csign for sensitive personal paperwork, including confidentiality agreements, creative collaborations, and side-letter deals, where they want a verifiable record but no third party reading along. Organisations can use the same flow for higher-stakes contracts where leak risk is a concern, such as supplier agreements or pre-deal documents shared between the two sides of a deal.
Roadmap items such as a public software interface have been put forward through Cardano's Catalyst funding programme but were not approved4, so the published feature set may move slowly. Anyone evaluating Csign for high-value use should test the public demo first and confirm pricing and account terms inside the live app.
