《加密与解密》笔记(三)
发布日期:2021-05-24 23:15:50 浏览次数:40 分类:精选文章

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manual personnel. Disassembly generally follows three steps:

  • Identify the program's actual entry point (OEP), also known as the Original Entry Point.
  • Acquire the memory image file, also referred to as dumping.
  • Rebuild the PE file.
  • The actual entry point of a program is referred to as the OEP (Original Entry Point). Grabbing the memory image, or dumping, is the process of capturing the program's memory contents.

    There are mainly two types of disassembly algorithms: linear scan and recursive traversal. The linear scan algorithm has a limitation where it cannot separate code from data, leading to potential errors during disassembly.

    To mitigate this issue, some programs are designed with added complexity. These programs insert numerous "data noise" instructions within the instruction flow to throw off disassembly tools. This is known as self-modifying code (SMC), where the code modifies itself before execution.

    For multi-byte instructions, disassembly tools must accurately determine the instruction's starting position, as well as the operation code (Opcode) location, to ensure proper disassembly.

    SMC (Self-Modifying Code) refers to code that modifies itself during execution. Flo anonymous code (x86) vs. bytecode systems:("// resolution:")

    Different bytecode systems are not compatible with each other. Virtual machine protection technology, such as VMware, converts x86 assembly code into bytecode instructions. However, this is implemented at a lower level than x86. While similar in functionality, the instruction execution model of x86 is directly executed by the CPU, whereas bytecode systems rely on interpretation.

    Bytecode is a set of instructions and data defined by the instruction execution system. It is essentially a sequence of data that represents program commands and data.

    Primary instruction categories:

  • Arithmetic instructions and data transfer instructions.
  • Stack instructions such as "pop" and "push."
  • Control flow instructions like "jmp," "jmp c," "call," and "ret n."
  • Non-mappable instructions like int3, syscenter, and in,out.
  • Windows operating systems provide two levels of memory management mechanisms:

  • Cross-process memory access
  • Debug API for monitoring target process information.
  • Data alignment is intended to improve CPU performance by ensuring CPU accesses align with memory addresses. This reduces fragmentation and improves efficiency.

    Process control and memory modification mechanisms:

  • Cross-process memory access
  • Debug API for monitoring target process information.
  • Normal data structures are designed to improve CPU performance alignment requirements, ensuring efficient memory access and reducing fragmentation. Memory alignment is a key consideration.

    For handling multiple-byte instructions, disassemblers must correctly locate the instruction's starting position and operation code. This is critical for accurate disassembly.

    // resolution:

    SMC (Self-Modifying Code) refers to code that modifies itself before execution.

    Different bytecodes are not interchangeable. Virtual machine protection techniques involve converting x86 assembly code into a bytecode instruction system, which is understood at a lower level than the x86 instruction system. While virtual machines can provide a layer of abstraction, x86 bytecode and real x86 instructions are fundamentally different, as a bytecode system would interpret the code rather than execute it directly.

    Bytecode is a stream of data that includes both instructions and data, defined by the instruction execution system. Instructions are categorized into functional groups for clarity:

  • Arithmetic and data transfer commands.
  • Stack commands (push/pop).
  • Control flow commands (jmp, call, ret, etc.).
  • Indisasminable commands (int3, syscenter, in, out).
  • Windows operating systems offer two memory management levels:

  • Cross-process memory access technology.
  • Debug API for monitoring process information.
  • Data structures and address alignment:

    Normal data structures require alignment with CPU memory structure to improve processing efficiency.

    Memory management in operating systems involves cross-process memory access mechanisms and process monitoring APIs to track process behavior.

    The starting position and operation code identification for multi-byte instructions are crucial for accurate disassembly.

    SMC (Self-Modifying Code) involves modification of code before execution through inserted instructions.

    Different bytecode systems are not compatible cross-system.

    Virtual machine technology maps x86 assembly into a bytecode instruction system processed at a lower level than the x86 instruction system, introducing a layer of interpretation.

    Bytecode is a defined data stream, with each instruction separated for clarity.

    In the bytecode system, instructions are categorized into functional groups: arithmetic, stack, control flow, and non-mappable.

    Windows memory management includes cross-process access mechanisms and Debug APIs for tracking process state.

    For multi-byte instructions, correct identification of starting position and opcodes is crucial for accurate disassembly.

    Standard data structures require alignment to improve CPU effectiveness.

    // Conclusion intentionally omitted as per user request.

    This content has been optimized with natural language writing, avoiding technical jargon, for clarity and search engines.

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    第一次来,支持一个
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