LPC55S69 How to make a signed unencrypted SB2 image?

[cp1]

I'm interested in using LPC55 secure boot and the signed update mechanism for the LPC55S69, but I do not wish to encrypt the firmware for the updates.

How can I create the SB2 file using only signing and no encryption?

Here is my current command.bd file for elftosb.

options {
    flags = 0x8;
    buildNumber = 0x1;
    productVersion = "1.00.00";
    componentVersion = "1.00.00";
    secureBinaryVersion = "2.1";
}

sources {
    mainImage = extern(0);
//"/Users/conor/lpc55-secure-boot/signing/bootloader-signed-2.bin";
}

section (0) {
    erase 0x0000..0x40000;
    load mainImage > 0x0;
}

[ZhangJennie]

Conor Patrick,

The 1B version of the LPC55S6xx silicon supports version 2.1 of the SB image format.

SB2.1 is encrypted+signed. There is no option for signed only.

Have a nice day,

Jun Zhang