Grafin User Guide

1) Purpose of the App

Grafin is a minimalist tool for local text encryption and decryption on your device. It helps you send confidential messages and store notes so that no one else can read them without the key. The app does not require the internet and does not collect any data.

2) How It Works

Grafin uses symmetric encryption AES‑256 (GCM mode), an industry-standard cryptographic algorithm. The same secret key is used for encryption and decryption. The key is derived from your phrase/combination of characters using PBKDF2. Learn more about AES encryption principles.

The browser version also encrypts your text locally, directly in your browser, without sending any data to the server. After the interface has loaded, you can disconnect the internet, physically unplug the cable from the router, and continue using it without interruption.

Grafin works cross‑platform — texts encrypted in the mobile app can be decrypted with the same key in the browser and vice versa.

3) How to Use

Encrypting Text

• Key field (top): enter or paste any combination of characters—words, numbers, emojis, any symbols. The more complex the key, the higher the entropy and the harder it is to guess. Choose a key that you and the recipient can comfortably use. The eye button hides the key from prying eyes.
• "YOUR TEXT" field (bottom): enter or paste the text you want to encrypt. The "Paste" button inserts from the clipboard, the "Clear" button empties the field.
• "Encode" button: click to encrypt the text with the entered key. The encrypted block will appear below; click it to copy.

Decrypting Text

• Enter or paste the same key that was used to encrypt the text.
• Paste the encrypted block into the "YOUR TEXT" field.
• Click "Decode" — the decrypted message will appear below.

Example Use Case #1 (Message Exchange)

1. You agree with a friend on a key in advance, e.g. "car 234". No one else knows it. The key can be shared through another independent channel (offline/another network).
2. In a messenger or social network, you want to share confidential information.
3. Open Grafin, enter the key, encrypt the message, and send the encrypted text.
4. Your friend pastes the received text into Grafin, enters the same key, and gets the original message.

Important: only you and the recipient know the key; without it, reading the content is nearly impossible.

Example Use Case #2 (Bypassing Link Filters)

1. A site forbids direct links (a filter is active).
2. You encrypt the link in Grafin with any key and post the encrypted text as a normal message.
3. You provide the key alongside. Anyone who needs the link can decrypt it in Grafin and access it.

Other Uses

• Storing personal encrypted notes.
• Transmitting code phrases, passwords, or hints (with caution and only to trusted people).
• Any scenario where confidentiality of content is important. You create the keys—they belong only to you.

Security Reminders

• Use long, non-trivial keys and keep them away from others.
• Do not use the same key forever; change it when necessary.
• Send the key and the encrypted text through different, independent channels.

For any questions or suggestions, please contact support: support@grafinonline.com