Preps for 1.6.0-rc1

[coverity]: https://scan.coverity.com/projects/mcuboot

[travis]: https://travis-ci.org/JuulLabs-OSS/mcuboot

This is mcuboot version 1.5.0

This is mcuboot version 1.6.0-rc1

MCUboot is a secure bootloader for 32-bit MCUs. The goal of MCUboot is to

define a common infrastructure for the bootloader, system flash layout on

- Table of Contents

{:toc}

## Version 1.6.0

The 1.6.0 release of MCUboot adds support for the PSOC6 platform,

X25519 encrypted images, rollback protection, hardware keys, and a

shared boot record to communicate boot attestation information to

later boot stages.  There are bug fixes, and associated imgtool

updates as well.

### About this release

- Initial support for the Cypress PSOC6 plaformt.  This platform

  builds using the Cypress SDK, which has been added as submodules.

- CBOR decoding in serial recovery replaced by code generated from a

  CDDL description.

- Add support for X25519 encrypted images.

- Add rollback protection.  There is support for a HW rollback counter

  (which must be provided as part of the platform), as well as a SW

  solution that protects against some types of rollback.

- Add an optional boot record in shared memory to communicate boot

  attributes to later-run code.

- Add support for hardware keys.

- Various fixes to work with the latest Zephyr version.

### Security issues addressed

- CVE-2020-7595 "xmlStringLenDecodeEntities in parser.c in libxml2

  2.9.10 has an infinite loop in a certain end-of-file situation." Fix

  by updating a dependency in documentation generation.

## Version 1.5.0

The 1.5.0 release of MCUboot adds support for encrypted images using

    "1.3.1": "v1.3.1"

    "1.4.0": "v1.4.0"

    "1.5.0": "v1.5.0"

    "1.6.0": "v1.6.0-rc1"

    "0-dev": "0.0.0"        # master

    "0-latest": "1.5.0"     # latest stable release