SABLE is a trusted bootloader which uses a TPM chip to establish mutual trust between a user and his/her platform. SABLE can be thought of as a wrapper for a GRUB2 menuentry, which can be used to attest to the integrity of that specific GRUB2 menuentry. For example, if a trusted kernel is corrupted or replaced by a malicious entity, SABLE provides a mechanism to inform the user that the boot configuration has been corrupted. This can be done for the kernel, or any arbitrary file.
SABLE is a component of a bigger picture. In particular, the Distributed Attestation for Mobile, Multicast & Multiple Operator Networks (DAM3ON) project that CTI is working on. SABLE utilizes the TPM by storing system measurements in Platform Configuration Registers (PCR), which DAM3ON can then use for remote attestation - as well as anonymous remote attestation. An example flow of starting from layer 0, to remote attestation, is shown in the diagram below