‘Marketed as the “world’s most secure handset,” ,’ banks, online shops, even WhatsApp use end-to-end encryption. What most people will see if they try and hack into the system is jumbled up data which is unintelligible.

The phones have two modes; normal operating mode and encryption mode. Operation Venetic was described by the NCA as “the biggest and most significant operation of its kind in the UK”. The NCA got into the system and read the messages.

You can read more about this here - https://www.thesun.co.uk/tech/12011641/how-encrochat-works-cops-crime-bosses-phone-system/