32 Bit - F1vm

| Opcode | Mnemonic | Operands | |--------|--------------|-------------------------| | 0x01 | MOV reg, imm | reg (1 byte), imm (4 bytes) | | 0x02 | ADD reg, reg | src, dst | | 0x03 | XOR reg, reg | | | 0x10 | PUSH reg | | | 0x11 | POP reg | | | 0x20 | JMP addr | 4-byte address | | 0x21 | JZ addr | jump if reg0 == 0 | | 0xFF | HALT | |

strings f1vm_32bit | grep -i flag No direct flag. But there’s a section: [+] Flag is encrypted in VM memory. f1vm 32 bit

f1vm_32bit (ELF 32-bit executable) 2. Initial Analysis file f1vm_32bit Output: Initial Analysis file f1vm_32bit Output: The VM initializes

The VM initializes reg0 as the bytecode length, reg1 as the starting address of encrypted flag. The flag is likely embedded as encrypted bytes in the VM’s memory[] . In the binary, locate the .rodata section – there’s a 512-byte chunk starting at 0x804B040 containing the bytecode + encrypted data. Here’s a detailed write-up for a (likely a

Here’s a detailed write-up for a (likely a custom or fictional VM challenge, similar to a reverse engineering or CTF problem). Write-Up: F1VM (32-bit) – Breaking the Fastest Virtual Machine 1. Introduction F1VM is a custom 32-bit virtual machine interpreter challenge. It implements a simple bytecode-based VM with 8 general-purpose registers, a stack, and a limited instruction set. The goal is to analyze the VM’s operation, understand the bytecode format, and retrieve a hidden flag.

25 73 12 45 9A 34 22 11 ... – that’s the encrypted flag. Write a simple emulator in Python to trace execution without actually running the binary.

ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), statically linked, stripped Check with strings :