Detailed Specifications

Host Tools

The host tools this year are created by the organizers and read-only. The host tools create a basic input/output format for communications between your devices and the host computer. More information on the host tools is available here.

Design Package

The Generate Secrets script must be implemented as a pip-installable Python package named ectf26_design.

Generate Secrets

Generate Secrets is a function that should be importable using:

from ectf26_design.gen_secrets import gen_secrets

The function takes a list of groups that will be valid in the system and returns any secrets that will be passed to future steps.

The full required interface is as follows:

def gen_secrets(groups: list[int]) -> bytes:
    pass

HSM Firmware

There are six required functional elements to the HSM firmware. These elements directly relate to the host tools:

• List Files

• Read a File from the HSM

• Write a File to the HSM

• Listen for Messages from a Neighboring HSM

• Interrogate Files from a Neighboring HSM

• Receive a File from a Neighboring HSM

All functional requirements must align with the Timing Requirements

File Allocation Table

The File Allocation Table (FAT) is used by the eCTF Bootloader to calculate cryptographic file digests. It must contain at least 8 of the following 24-byte struct where each entry corresponds to a file slot. The FAT must be based at the flash address 0x3a000.

FAT

Offset	Size	Name	Description
0x0	16	UUID	UUID of the file in that slot
0x10	2	Length	Length of the file
0x12	2	Padding	Unused to pad to 32-bit alignment
0x14	4	Addr	Starting flash address of the file

Flash Layout

Flash Layout

Offset	Size	Name	Description
0x0	0x6000	Bootloader	Reserved for the eCTF bootloader
0x6000	0x34000	APP1	Flash region that may be used by your design however you see fit. The IVT must be loaded from the base of this region
0x3A000	0x400	File Allocation Table	This page MUST store the File Allocation Table
0x3A400	0x5c00	APP2	Flash region that may be used by your design however you see fit.

Detailed Requirements

The following constraints must be met:

Permission Strings

At build time, a string representing the permission set is provided (e.g., 1234=RW-:aabb=RWC:1a2b=--C).

Permission list: The string shall be a colon-separated list of permissions (e.g., <perm1>:<perm2>:<perm3>).

Permission entry: Each entry shall be a pair of group ID and permissions separated by an equal sign (e.g., <group_id>=<permission>).

Group ID: The group ID shall be a 16-bit hexadecimal number padded with 0s to be a total of 4 characters with no preceding ‘0x’ (e.g., 4b1d).

Permission: The permission shall be a 3-character string where present permissions are represented by their opcode and absent permissions are represented by a ‘-’ (e.g., RWC, RW-, --C).

PINs

A PIN shall be exactly 6 lowercase hexadecimal characters (0-9, a-f).

Timing Requirements

Operation	Maximum Time for Completion
Device Wake	1 second
List Files	500 milliseconds
Read File	1000 milliseconds
Write File	1000 milliseconds
Receive File	2000 milliseconds
Interrogate	1000 milliseconds
Any Operation Where an Invalid PIN is Provided	5 seconds

File Size Requirements

Component	Size
Group ID	16 bits
File UUID	16 bytes
File Name	Max 32 bytes
File Content Size	Max 8192 bytes

File Storage Requirements

File Slots

8 slots

Deployment Requirements

Number of supported group ids

32 groups

Allowed Programming Languages

To build the firmware your design, your team may choose to implement your design in any compatible language. To align with good development practices, you must not use a language that was specifically chosen to be difficult to understand.

The pre-approved programming languages are: C, C++, and Rust. If you wish to use a different language, please reach out to the organizers first.

Be aware that if your team decides to use a language which incorporates a panic handler, your design must still adhere to the Timing Requirements and should not enter an infinite loop in response to any normal input.

The Reference Design was created in C, and as such if your team decides to use another programming language, the Dockerfile must be updated to allow for the organizers and teams to be able to build and utilize your design.