I heard that the x86 NOP instruction can be represented in multiple ways.
Beginner Hint: Approach to Solving the Challenge
Intel® 64 and IA-32 Architectures Software Developer's Manual Combined Volumes 2A, 2B, 2C, and 2D: Instruction Set Reference, A- Z, mentioned in a comment inchal.py, is an excellent resource.- To understand the structure of machine code in x86, see
Figure 2-1. Intel 64 and IA-32 Architectures Instruction Formatin the resource. - To understand the structure of the machine code for
known_nopinchal.py, see theNOP—No Operationinstruction andTable 4-12. Recommended Multi-Byte Sequence of NOP Instructionin the resource. - Finally, to consider how to satisfy the requirements in
chal.py, seeTable 2-2. 32-Bit Addressing Forms with the ModR/M ByteandTable 2-3. 32-Bit Addressing Forms with the SIB Bytein the resource.