This is a pet hate of mine. I get an SMS. Somebody is asking me something, and it involves them admitting to committing a crime (hypothetically.)
Example: The idiot who texted me asking if I could help them cook crystal methylamphetamine (knowing I have studied chemistry.)
What has that idiot done? First, they just stated that they are intending to commit an offence and are asking me to commit an offence violating the NSW Drug Misuse And Trafficking Act 1985 No. 26, section 19:
Aiding, abetting etc commission of offence in New South Wales
(1) A person who aids, abets, counsels, procures, solicits or incites the commission of an offence under this Division is guilty of an offence and liable to the same punishment, pecuniary penalties and forfeiture as the person would be if the person had committed the firstmentioned offence.
Secondly, SMS metadata is retained on all Australians for two years by law. Thirdly, it would be easy to subpoena the contents of SMS messages as the message alone is at least reasonable suspicion, if not probable cause (circumstances dependent.)
How to communicate safely if something that could be taken the wrong way needs to be discussed?
SMS is not safe, not encrypted. Your phone calls are not. Snapchat isn’t, Facebook isn’t (it’s “end to end encrypted messages are not), Viber isn’t. Telegram is a not good, but slightly better. iMessage is about the same, don’t trust it. WhatsApp is OK, but not great.
Wickr is quite good. It doesn’t require a phone number. Recommended.
SIgnal, requires a phone number, but is regarded as the most secure. Highly. Recommended.
Turn on self destructing messages. Give them a day maybe to last, and no more than an hour to burn after reading.
PGP encrypted messages/email: Not self destructing, but they use strong public-key encryption and do not require the two parties to have communicated before or to have ever met in any way. Cryptographic signatures from other users, building a web of trust, establish to legitimacy of these keys as belonging to and being controlled by the owner.