patch3

rev_kids20

Task: tiny hand-written MASM PE32 crackme that reads stdin, transforms the first DWORD, and compares to a magic constant. Solution: spot the self-modifying patch (sub [op],0xf) that redirects the hash routine's final jmp to two hidden transform steps (ror 7; xor), reconstruct the full 7-step bijection, brute-force the 32-bit preimage of 0xca9d63fe to get 0x79627572 = little-endian ASCII 'ruby'.