This just goes to show that you can't trust any messaging app or phone to be "secure".
Imagine if there was a small handheld device that you could type messages into (along with a secret phrase or a private key), and it would spit out a string of encrypted text that could be entered into ANY messaging app (or even published publicly on a billboard if you wanted). You could even encode the encrypted text as a scannable QR code if you wanted.
On the receiving side of things, the decrypter device could have a camera that could read QR codes (or maybe OCR an encrypted string of text). The most basic solution would be to type the entire encrypted string of text into the box and then enter the secret pass phrase or key to decrypt it.
The point, however, is that the encryption and decryption HAVE to be done on a separate hardware device that is air-gapped and does NOT have internet access in any way.
If we're being paranoid that separate device could also be compromised so that the messages could be decrypted with another key other than the main key(s) used by either party.
Imagine if there was a small handheld device that you could type messages into (along with a secret phrase or a private key), and it would spit out a string of encrypted text that could be entered into ANY messaging app (or even published publicly on a billboard if you wanted). You could even encode the encrypted text as a scannable QR code if you wanted.
On the receiving side of things, the decrypter device could have a camera that could read QR codes (or maybe OCR an encrypted string of text). The most basic solution would be to type the entire encrypted string of text into the box and then enter the secret pass phrase or key to decrypt it.
The point, however, is that the encryption and decryption HAVE to be done on a separate hardware device that is air-gapped and does NOT have internet access in any way.