Download the code to your machine using:
$ git clone https://github.com/embsec/design-challenge-2022-arthur-initialization-vector-robinson.git
Update Pycryptodome to the latest version with:
$ python -m pip install -U pycryptodome
Build firmware using
$ cd firmware/firmware
$ make
Build the bootloader with
$ cd tools
$ python bl_build.py
$ python fw_protect.py --infile ../firmware/firmware/gcc/main.bin --outfile ../f_prot.bin --version 3 --message "this is a release message!"
Frame Size:
x represents some number of padding depends on the how large the encoding of firmware is
| 16 Tag | 16 Nonce | 64 ECC key | 2 bytes Version | 2 bytes Firmware Length | x Firmware | x Message | 1 Null | x Padding | 64 Padding |
This was the process of encrypting our firmware to maintain the triad of cybersecurity CIA: Confidentiality, Integrity, and Authorization.
This was the overview of how we wanted to decrypt and flash a new firmware into memory.
Security process:
We encrypted our firmware using AES-GCM because we wanted to keep the security of AES-CBC which adding an additional authorization factor which GCM provided. AES GCM is a symmetric cipher that uses mathematical properities to ensure data obscurity through confusion and diffusion.
We also wanted to provide an additional layer of security as most teams were implementing the RSA public-private key pairs to ensure authenticity, however, we took this one step further. We applied a new technology called Eliptical Curve Cryptography which has higher security than RSA and implements higher levels of math.
Our last method to ensure total security, and just make our own lives slightly more difficult, was the Vignere Cipher. The Vigenere Cipher is a symmetric cipher which originally utilizes an alphabet table that scrambles data with a predetermined key. However, because we are using raw bytes instead of letters, we decided to implement it with the xor function because that would randomize it enough.
The entire encryption process in pseudocode looks like this:
Signed_Data = ECC_Encrypt(Metadata + Firmware + Message + Padding)
#We want to sign then encrypt because otherwise hashing is basically worthless
AES_Encrypted_Data = AES_Encrpyt(ECC_Signature + Signed_Data)
#Encrypting the signature so it cannot be tampered with
Vig_Encrypted_Data = Vigenere_Encrypt(AES_Encrypted_Data)
#Encrypting with Vigenere because we're extra
Final_Packet = Tag + Nonce + Vig_Encrypted_Data + Null_FrameThe entire decryption process in pseudocode looks like this:
Tag = Received_Decryption[:12]
Nonce = Received_Decryption[12:]
#This is sent first, separate from the rest of the blob, the rest is received in frames of 64
Vig_Decrypted_Data = Vigenere_Decrypt(Received_Blob)
#Decrypt Vigenere
AES_Decrypted_Data = AES_Decrypt(Tag, Nonce, Vig_Decrypted_Data)
#Decrypt AES using Tag and Nonce
ECC_Signature = AES_Decrypted_Data[:64]
Encrypted_Firmware_Blob = AES_Decrypted_Data[64:]
#Extract ECC data
Unencrypted_Firmware_Blob = ECC_Verify_And_Decrypt(ECC_Signature)
#Verify our ECC signature
Version = Unencrypted_Firmware_Blob[:2]
Firmware_Size = Unencrypted_Firmware_Blob[2:4]
Firmware = Unencrypted_Firmware_Blob[4:Firmware_Size+4]
Message = Unencrypted_Firmware_Blob[Firmware_Size+4:]
#Unpack the entire Firmware blob' $$\ $$\ $$\ $$\ $$$$$$\ $$\ $$\ $$\ $$\ $$\ $$\ $$\
' $$ | $\ $$ | $$ | $$ | \_$$ _| $$ | $$ | $$ | $$ |\__| \__| $$ |
' $$ |$$$\ $$ | $$$$$$\ $$$$$$\ $$$$$$\ $$$$$$\ $$$$$$\ $$$$$$$\ $$$$$$\ $$ |$$\ $$\ $$$$$$$\ $$$$$$\ $$$$$$$\ $$$$$$$ | $$\ $$\ $$\ $$$$$$\ $$$$$$\ $$$$$$\ $$$$$$\ $$$$$$$\ $$$$$$\ $$$$$$\ $$$$$$\ $$$$$$\ $$$$$$\ $$$$$$\ $$ |$$\ $$$$$$\$$$$\ $$\ $$$$$$$\ $$$$$$\ $$$$$$\ $$$$$$\ $$\ $$\ $$$$$$\ $$\ $$\
' $$ $$ $$\$$ |$$ __$$\ \____$$\ $$ __$$\ $$ __$$\ \_$$ _| $$ __$$\ $$ __$$\ $$ |\$$\ $$ |$$ _____| \____$$\ $$ __$$\ $$ __$$ | $$ | $$ | $$ |$$ __$$\ \____$$\ $$ __$$\ $$ __$$\ $$ __$$\ $$ __$$\ $$ __$$\ $$ __$$\ \_$$ _| $$ __$$\ $$ __$$\ $$ |$$ |$$ _$$ _$$\ $$ |$$ __$$\ \____$$\\_$$ _| $$ __$$\ $$ | $$ |$$ __$$\ $$ | $$ |
' $$$$ _$$$$ |$$$$$$$$ | $$$$$$$ |$$ | \__|$$$$$$$$ | $$ | $$ | $$ |$$$$$$$$ | $$ | \$$\$$ / \$$$$$$\ $$$$$$$ |$$ | $$ |$$ / $$ | $$ | $$ | $$ |$$$$$$$$ | $$$$$$$ |$$ | \__|$$$$$$$$ | $$ | $$ |$$$$$$$$ |$$ | \__|$$$$$$$$ | $$ | $$ / $$ | $$$$$$$$ |$$ |$$ |$$ / $$ / $$ |$$ |$$ | $$ | $$$$$$$ | $$ | $$$$$$$$ | $$ | $$ |$$ / $$ |$$ | $$ |
' $$$ / \$$$ |$$ ____| $$ __$$ |$$ | $$ ____| $$ |$$\ $$ | $$ |$$ ____| $$ | \$$$ / \____$$\ $$ __$$ |$$ | $$ |$$ | $$ | $$ | $$ | $$ |$$ ____| $$ __$$ |$$ | $$ ____| $$ | $$ |$$ ____|$$ | $$ ____| $$ |$$\ $$ | $$ | $$ ____|$$ |$$ |$$ | $$ | $$ |$$ |$$ | $$ |$$ __$$ | $$ |$$\ $$ ____| $$ | $$ |$$ | $$ |$$ | $$ |
' $$ / \$$ |\$$$$$$$\ \$$$$$$$ |$$ | \$$$$$$$\ \$$$$ |$$ | $$ |\$$$$$$$\ $$$$$$\ \$ / $$$$$$$ | \$$$$$$$ |$$ | $$ |\$$$$$$$ | \$$$$$\$$$$ |\$$$$$$$\ \$$$$$$$ |$$ | \$$$$$$$\ $$ | $$ |\$$$$$$$\ $$ | \$$$$$$$\ \$$$$ |\$$$$$$ | \$$$$$$$\ $$ |$$ |$$ | $$ | $$ |$$ |$$ | $$ |\$$$$$$$ | \$$$$ |\$$$$$$$\ \$$$$$$$ |\$$$$$$ |\$$$$$$ |
' \__/ \__| \_______| \_______|\__| \_______| \____/ \__| \__| \_______| \______| \_/ \_______/ \_______|\__| \__| \_______| \_____\____/ \_______| \_______|\__| \_______| \__| \__| \_______|\__| \_______| \____/ \______/ \_______|\__|\__|\__| \__| \__|\__|\__| \__| \_______| \____/ \_______| \____$$ | \______/ \______/
' $$\ $$ |
' \$$$$$$ |
' \______/
Team Arthur Intialization Vector Robinson presents: The Super Secure Embedded Bootloader Firmware ThingTM