12.4.4 Zigbee OTAU Image File Definition

Zigbee OTAU File contains the OTAU header and Upgradable Flash Image. This file is loaded into OTAU Server connected PC tool to send to OTAU Client over zigbee mesh network.

• Flash Image: Meta-data Header + Executable Firmware. This is Full image content which is programmed in the device Flash Slot1.

• Meta-data Header: Flash Image will have a metadata header, metadata payload and metadata footer that will give the Bootloader firmware information about where the firmware image is located, security decryption information, signature, sequence number etc. Digital signatures ensure the authenticity of the image and integrity of the data in the image. A digital signature also ensures that the data within the image has not been modified (preserving integrity) and is intact as it was generated at the source. Refer to meta data header format from stack document)

• OTAU File Encryption: The executable firmware can be encrypted (This is configurable). Encrypting the image ensures the confidentiality of the data. This makes that no unauthorized parties are able to peek at the contents of the image. Only the end-device should be able to decrypt the image. AES128-CBC method of encryption is used. Only the firmware image is encrypted and OTAU Header is not encrypted.

• Zigbee OTAU Header: This header is as per zigbee OTA specification. The below is the extract from the specification.

Figure 12-47. .

OTA file is .zigbee file which can be generated from MPLABX Tools environment as shown below. The detail steps for image generation is explained later.

Zigbee OTAU Header and Encryption Key Configuration:

Figure 12-48. .

Meta-data Header Configuration:

Figure 12-49. .