01 Protect · runs on this page
Vault
Turn a note or a file into AES-256-GCM ciphertext on your own device, locked by a passphrase or a key you make.
Ciphertext—
…
AES-256-GCM · new 12-byte nonce on every keystroke key stays in this tab
Protect what matters.Share what you choose.
Cypra seals files and notes in your browser, lets you share them by link without handing the key to a server, and records who you allowed to read them on Robinhood Chain.
Between a guess and your key
600,000
rounds of PBKDF2-SHA-256 run on your device before a passphrase becomes a key, so every wrong guess costs an attacker the same work.
OWASP password storage guidance ↗NetworkRobinhood Chain · 4663
Blockreading…
Gasreading…
EncryptionIn your browser
Records—
01The problem
Most leaks happen after the upload.
An attachment or a cloud link can be read by every server it passes and every account that gets the link. Cypra seals the file before it leaves your device, so what travels is ciphertext and the key never sits next to it.
01AES-GCM
256
bit keys seal every file, using the browser's own WebCrypto engine rather than a script we wrote.
WebCrypto · AES-256-GCM
02Integrity
16
byte tag guards every 1 MiB chunk. Change one bit, swap two chunks or cut the file short and it refuses to open.
Tested: tamper, reorder, truncation
03Commitment
0
copies of your passphrase or key kept by Cypra. Not for support, not for recovery, not ever.
Our commitment
Record · sample Access set
File
sealed.
- Plaintext sent
- 0 bytes
- Readers granted
- 2 addresses
- Revoked in
- 1 signature
One file · one key
Cypra seals what you decide to share and keeps a public note of who may read it, starting with the file you are about to send.
Seal a file02Toolkit
Seal it here. Share it anywhere.
Each tool does one job you can check for yourself. Two of them run right on this page, and nothing you type here is sent anywhere.
03 Protect · runs on this page
Key Management
Make 256-bit keys, check them by fingerprint, export them wrapped under a passphrase and move files to a new key.
Fingerprint—
···· ···· ···· ····
Press the button: a fresh key appears, made on this device and forgotten when you leave.
crypto.getRandomValues · fingerprint = SHA-256, first 8 bytes
The full Terminal
Six more tools. One sealed file in.
01 / 06
03Key lifecycle
Your passphrase makes the key. Nobody keeps a copy.
Encryption is only as strong as the secret behind it. Here is what happens to a file from the moment you seal it, and which parts become public along the way.
- 01 · Seal
Only ciphertext leaves
Your browser turns the file into a sealed container. What you send, upload or store is noise to anyone without the key.
- 02 · Anchor
The hash goes public
Anchoring writes the file's hash and your address on Robinhood Chain. Anyone can see that a record exists; nobody can read the file from it.
- 03 · Lose
No key, no file
There is no reset link. If the passphrase or key is gone, the sealed file stays sealed, for you and for everyone else.
Life of a sealed file · sample01 / 03
Ciphertext hash (keccak-256)Only on your device
0x7c1e 92af 03d4 b8e6 51c0 9f2a e4d7 3b18 a6f0 2c95 d1e3 7b4a 08f6 c2d9 5e17 a3b0
Sealed bytesUnreadable without the key
c9 4f e2 07 1a d8 6b 30 f5 9c 2e 81 b7 46 0d e9 73 aa 15 c4 58 9f 2b e0 d6 31 7e 4c a2 08 fb 95
Passphrase or keyYours alone
•••• •••• •••• •••• •••• •••• ••••
What is protected, what is not
| Item | Where it lives | Status |
|---|---|---|
| File contents | Sealed in your browser | ● Encrypted |
| File name and type | Inside the sealed payload | ● Encrypted |
| Approximate size | Readable from the sealed file | ◆ Public |
| Ciphertext hash | On chain, once you anchor | ◆ Public |
| Addresses you grant | On chain, once you grant | ◆ Public |
| Passphrase or key | Your device only | ● Never sent |
Public means anyone can read it on Robinhood Chain, and it stays there.
Standards behind it
- Sep 2000
RFC 2898 publishes PBKDF2, the passphrase-to-key method Cypra uses. source
- Nov 2001
NIST publishes AES as FIPS 197, the block cipher under every sealed chunk. source
- Nov 2007
NIST SP 800-38D defines GCM, the mode that both encrypts and detects tampering. source
- Jan 2017
RFC 8018 updates the PBKDF2 specification (PKCS #5 v2.1). source
- Jan 2017
The W3C Web Cryptography API becomes a Recommendation, so browsers run these primitives natively. source
- Today
OWASP's password storage guidance lists 600,000 rounds for PBKDF2 with SHA-256, the count Cypra uses. source
04How it works
From file to shared, on your terms.
- 01
Choose
Pick a file or type a note. No account and no wallet are needed to start.
- 02
Seal
A key comes from your passphrase or the browser's random source, and AES-256-GCM seals the content chunk by chunk.
- 03
Share
Send the sealed file, or a link whose key sits after the #. The reader opens it in their own browser.
- 04
Record
If you want proof, anchor the file's hash and grant or revoke readers on Robinhood Chain from your wallet.
05$CYPRA
$CYPRA, planned as service credits.
The plan is for $CYPRA to pay for hosted storage, API calls and premium tools. None of that is switched on: every tool on this site is free today and nothing reads your balance.
- Ticker
- $CYPRA
- Chain
- Robinhood Chain (4663)
- Type
- ERC-20 token, only ever read by this site
- Contract
- Contract address coming soon
- Supply
- —
ETH—Chainlink feed on Robinhood Chain
06Built on Robinhood Chain
EVM-compatible, quick to confirm, and settled to Ethereum.
Robinhood Chain runs as a layer 2 on top of Ethereum, using the Arbitrum stack. Addresses and keys work exactly as they do on Ethereum, so the wallet you already use can sign Cypra access records with nothing new to install.
Cypra pulls blocks and records from the public RPC endpoint and links each record to the Blockscout explorer ↗. Writing a record costs a little ETH as gas; reading one is free.
Cypra is an independent project: Robinhood has not endorsed, sponsored or partnered with it.
07FAQ
Plain answers.
Short and checkable. If an answer here is not true of the product, treat it as a bug and tell us on X.
01What is Cypra?
Cypra is a set of browser tools for sealing files and notes with AES-256-GCM, sharing them by link, managing the keys, and recording on Robinhood Chain who you allowed to read them. Encryption and decryption happen in your browser; the site never receives your plaintext, your passphrase or your key.
02Do I need a wallet?
No. Sealing, sharing and key work need no wallet at all. You only sign with one when you write an access record on chain, and that costs a little ETH as gas.
03What happens to my data when I seal it?
It stays with you unless you send it. Sealing happens in the tab. If you use a share link and this site has storage switched on, only the sealed bytes are uploaded; the key sits after the # in the link, a part browsers never send to a server.
04Do on-chain permissions stop someone from opening a file?
No. A grant on chain is a public statement of who you allowed, with a time and your address behind it. It does not enforce decryption: anyone who holds the sealed file and its key can open it. Only hashes and addresses go on chain, never the file or the key.
05Can you recover a lost passphrase or key?
No. Cypra keeps no copy. Lose the passphrase or key and the sealed data stays sealed for good. Export your keys wrapped with a passphrase and keep that backup somewhere you control.
06What will $CYPRA be used for?
The plan is service credits, API access and premium features. None of it is active: every tool here is free and nothing reads your balance. $CYPRA gives no ownership, no share of revenue and no promised return.