RSA Encrypt/Decrypt Tool

Instructions

1. Keys are created automatically:
   When the page loads, a personal RSA keypair is generated and stored in your browser's localStorage.
2. View your keys:
   - Click Show My Public Key to reveal your public key (share this with others).
   - Click Show My Private Key to reveal your private key (keep this secret).
3. Encrypt a message for someone else:
   Paste the recipient's public key into the Public Key (others') box. Enter your message in the Plaintext to Encrypt box and click Encrypt. The ciphertext will appear in the Ciphertext box.
4. Send the ciphertext:
   Copy the text from the Ciphertext box and send it to the recipient. Only their private key can decrypt it.
5. Decrypt a message for you:
   Paste ciphertext (that was encrypted with your public key) into the Ciphertext box. Click Decrypt. The plaintext will appear in the Decrypted Output box.
6. Regenerate keys:
   Click Generate New Keypair if you want to replace your keys. Warning: old messages encrypted for your previous keypair will no longer be decryptable unless you saved that private key.
7. Usage:
   RSA is length limited, so use it to share a short AES key instead of full messages.
   Copy the 32-byte AES key (base64) from the AES tool -> paste it into Plaintext to Encrypt here -> click Encrypt -> send the ciphertext.
   The recipient decrypts it and pastes the result back into their AES tool's key field.

How It Works

• RSA uses two keys: a public key (shared) and a private key (kept secret).
• Anyone can use your public key to encrypt messages that only your private key can unlock.
• Messages are encrypted with RSA-OAEP (SHA-256, 2048-bit modulus).
• Because of RSA padding limits, messages must be < 190 bytes (UTF-8 encoded).
• Your keys stay in your browser's localStorage and are not uploaded anywhere.