Technically you don't even need a second memory card. Some SD cards have suitable processors in them already. Edit: Google's Vault [0] is a custom hardware imp

Technically you don't even need a second memory card. Some SD cards have suitable processors in them already. Edit: Google's Vault [0] is a custom hardware implementation of this concept. [0] https://techcrunch.com/2015/05/29/googles-project-vault-is-a-secure-computing-environment-on-a-micro-sd-card-for-any-platform/ https://techcrunch.com/2015/05/29/googles-project-vault-is-a...