Add PGP support
iOS does not allow the creation of SMS apps, but there are apps for iOS such as PGP Everywhere which allow uses to easily communicate via SMS using PGP for encryption.
I think if Silence should consider also adding OpenPGP support by adding these features...
- Create a private key for your phone number
- Import/export your phone number private key
- Upload your public PGP key to keys.openpgp.org
- Easily share your public PGP key in a text message (Same as invite button does but shares your public PGP key)
- Contact List to save public PGP keys of phone numbers you communicate with
- Import/Export contact list public PGP keys
- After every edit of your contact list, it will remind you to make a backup of your contacts list
This way Silence can easily communicate with iOS users using a encryption standard that is common in email and has also been used is SMS. It is possible to use apps such as OpenKeychain on Android but this app will require you to copy the text message and paste it into the OpenKeychain to decrypt the message, since Android allows you to develop SMS apps, why not have a SMS app that does all the encryption and decryption for you within the app.
I still think Signal should still be used for communication between Android Silence to Android Silence users since Signal is seamless and is strong.