🔐 How PasteDB End-to-End Encryption Works

1. Account Setup

• A new RSA key pair is generated in your browser.
• A random KEK (Key Encryption Key) is generated.
• The KEK is encrypted using your RSA public key.
• The server stores:
  • RSA public key
  • Encrypted KEK
• The plaintext KEK is stored locally in IndexedDB as accountKEK.

Browser
 ├─ Generate RSA Key Pair
 ├─ Generate KEK
 ├─ Encrypt KEK
 ├─ Upload Public Key + Encrypted KEK
 └─ Store accountKEK in IndexedDB

2. Creating an Encrypted Paste

• A random PEK (Paste Encryption Key) is generated.
• The PEK encrypts the paste title, content and images array.
• The PEK itself is encrypted with the account KEK.
• The server receives:
  • Encrypted title
  • Encrypted content
  • Encrypted images array
  • Encrypted PEK
  • Paste metadata

Generate PEK
      │
Encrypt Title / Content / Images
      │
Encrypt PEK using KEK
      │
Upload Everything

3. Why Metadata Isn't Encrypted

Only the title, content and images array are encrypted. Metadata remains readable because the server needs it to provide core functionality such as syntax highlighting, visibility rules, timestamps, ownership, expiration, searching and other application features.

4. Retrieving an Encrypted Paste

• Download encrypted paste.
• Load accountKEK from IndexedDB.
• Decrypt the encrypted PEK.
• Use the PEK to decrypt the title, content and images array.
• Display the plaintext in the browser.

Download Encrypted Paste
          │
Load accountKEK
          │
Decrypt PEK
          │
Decrypt Title / Content / Images
          │
Display Paste

5. Sharing Unlisted Encrypted Pastes

For unlisted encrypted pastes, the PEK is appended to the URL fragment (#...). URL fragments are processed by the browser and are not sent to the server during HTTP requests.

https://pastedb.netlify.app/paste/abc123#PEK

What the Server Can See

• Metadata
• Encrypted title
• Encrypted content
• Encrypted images array
• Encrypted PEK
• RSA public key

What the Server Cannot See

• Plaintext title
• Plaintext content
• Plaintext images
• KEK
• PEK (unless intentionally shared through the URL fragment)

Summary

Your browser performs all encryption and decryption. PasteDB stores encrypted data and the metadata required for application features, but never has access to your plaintext title, content or images.