MARS: Prototype emulator of TCG MARS spec
Author: Tom Brostrom

Builds MARS dispatchers using Ascon, AUTOSAR SHE, SHA2, SHA3

BUILD INSTRUCTIONS

    Download MARS repository
        wget https://github.com/TrustedComputingGroup/MARS/archive/refs/heads/main.zip
        unzip main.zip
        rm main.zip
        mv MARS-main mars

CBOR:
    cd .../mars/emulator
    wget https://github.com/intel/tinycbor/archive/refs/tags/v0.6.0.zip
    unzip v0.6.0.zip
    rm v0.6.0.zip
    mv tinycbor-0.6.0 tinycbor
    cd tinycbor/src
    gcc -c -Os -fpic *.c
    gcc -shared -o ../../build/libtinycbor.so *.o -lm

Ascon:
    cd .../mars/emulator
    wget https://github.com/TheMatjaz/LibAscon/archive/refs/tags/v1.2.0.zip
    unzip v1.2.0.zip
    rm v1.2.0.zip
    mv LibAscon-1.2.0 ascon
    cd ascon/src
    gcc -c -Os *.c -I../inc -std=c99
    ar r ../../build/ascon.a *.o

AES:
    cd .../mars/emulator
    wget https://github.com/kokke/tiny-AES-c/archive/refs/tags/v1.0.0.zip
    unzip v1.0.0.zip
    rm v1.0.0.zip
    mv tiny-AES-c-1.0.0 aes
    # below's make will build

SHA2:
    Requires openssl (tested on 1.0.2)
    if openssl3 is downloaded:
    cd .../mars/emulator
    mv openssl/openssl-openssl-3.0/libcrypto.so.3 build/

SHA3:
    Requires openssl (tested on 3.0)

make
    cd .../mars/emulator/c
    make
	# executables --> ../build

To run:
    in one window:
    export LD_LIBRARY_PATH+=:<full_path_to>/mars/emulator/build
    # start a dispatcher, one of: dispa (with ascon), disps (with SHE)
    # disp2 (with SHA2), disp3 (with SHA3)
    ../build/dispa

    in another window:
    ../build/demo

ARCHITECTURE

The layering of software used here is as follows, and is described below:

	APPLICATION
	MARS
	CRYPT PRIMITIVES
	BASE CRYPTOGRAPHIC ALGORITHMS

ARCHITECTURE.BASE CRYPTOGRAPHIC ALGORITHMS

The algorithms implemented here were envisioned to be, but not limited to, those implemented in microcontroller hardware as an internal peripheral to accelerate specific cryptographic operations. These algorithms form the basis for which all cryptographic processing is done by MARS.

The base algorithms used here are SHA256 and Ascon.

ARCHITECTURE.CRYPT PRIMITIVES

These so-called "crypt" primitives are those required by MARS. They are documented in the MARS Library Specification as Support Functions. "Crypt" functions are constructed using the base algorithms.  Those functions share a common prefix and are named:

CryptHashInit, CryptHashUpdate, CryptHashFinal
- produce a fixed-size digest as a result of hashing variable length input

CryptSign - signs a provided digest

CryptVerify - determines if a signature is valid for the provided digest and the specified signing key

CryptSkdf - derive a Symmetric key 

CryptAkdf - derive an Asymmetric key

CryptXkdf - performs CryptAkdf if implemented, otherwise CryptSkdf

Source code implementing the crypt functions are found in hw_*.c.

Examples include hw_ascon.c and hw_she.c.


ARCHITECTURE.MARS

The emulator for MARS and the API is found in mars.c. MARS is crypt-agnostic and can be viewed as a state machine that orchestrates the Crypt layer to function as a root-of-trust.

mars.c is compiled for the appropriate Crypt layer by pre-including that layer's header file. This can be seen in the Makefile where the "-include" argument is used with gcc.


ARCHITECTURE.APPLICATION

Application code built upon MARS is available as simple demonstration programs. Refer to demo*.c.