Firmware decryption tool for OP-1

This tool allows the decryption of the OP-1 firmware. Especially the file OP1_vdk.ldr. In that file every boot stream block with the flag BFLAG_CALLBACK is encrpyted using the XTEA algorithm. For every 24 byte block only the first 8 byte are encrypted and the remaining 16 bytes are unencrypted.

Compilation

Compile with gcc

gcc -o decrypt decrypt.c

Usage

Key, input file and output file needs to be provided as parameters

decrypt [key] [input] [output]

Key

The key is a 16 byte in length and must be provided as 32 character hexadecimal string on the command line.