While the iPhone Notes app doesn’t have built-in end-to-end encryption, you can use a simple workaround to send secret messages:

1. Create a Password-Protected Note:

• Open the Notes app on your iPhone.

• Tap the “New Note” button.

• Type your secret message in the note.

• Tap the “Share” button (looks like a square with an upward arrow).

• Select “Lock Note.”

• Set a password for the note and confirm it.

2. Share the Note Securely:

• You have a few options to share the note securely:

  * AirDrop: If you’re near the recipient, use AirDrop to share the note. Make sure AirDrop is set to “Everyone” on both devices. 

  * Email: Send the note as an email attachment.

  * Other Secure Sharing Methods: You could use a secure messaging app (like Signal or WhatsApp) or a file-sharing service (like Dropbox or Google Drive) to share the note, ensuring the recipient has to unlock it with the password.

3. Access the Note on the Other Device:

• The recipient will receive the locked note.

• They will need to open the note and enter the password you set to view the secret message.

Important Considerations:

• Password Security: Choose a strong password that’s difficult to guess.

• Note Protection: The note itself is only protected by the password. If someone gets ahold of the device with the unlocked note, they can see the message.

• No End-to-End Encryption: This method doesn’t provide true end-to-end encryption like a secure messaging app does. 

Alternatives for Secure Messaging:

• Secure Messaging Apps: For true end-to-end encrypted messaging, use apps like Signal, WhatsApp (for encrypted group chats), or Telegram.

This method is a simple way to send secret messages using your iPhone’s Notes app, but it’s not as secure as using a dedicated encrypted messaging app. Always choose the most appropriate method for the level of security you need.