好吧，我研究了Delphi中的一些内联汇编，并且汇编加密例程进展顺利，直到我尝试将ShortString解析到Textbox中为止。
我得到的违规如下：
完整的代码在这里：
procedure TForm2.Button1Click(Sender: TObject);
var
len,keylen:integer;
name, key:ShortString;
begin
name := ShortString(Edit1.Text);
key := '_r <()<1-Z2[l5,^';
len := Length(name);
keylen := Length(key);
nameLen := len;
serialLen := keyLen;
asm
XOR EAX,EAX
XOR ESI,ESI
XOR EDX,EDX
XOR ECX,ECX
@loopBegin:
MOV EAX,ESI
PUSH $019
CDQ
IDIV DWORD PTR DS:[serialLen]
MOV EAX,ESI
POP EBX
LEA ECX,DWORD PTR DS:[key+EDX]
CDQ
IDIV DWORD PTR DS:[nameLen]
LEA EAX,DWORD PTR DS:[name]
MOVZX EAX,BYTE PTR DS:[name+EDX]
MOVZX EDX,BYTE PTR DS:[ECX]
XOR EAX,EDX
CDQ
IDIV EBX
ADD DL,$041
INC ESI
CMP ESI,DWORD PTR DS:[serialLen]
MOV BYTE PTR DS:[ECX],DL
JL @loopBegin
end;
edit2.Text:= TCaption(key);
end;
如果我在“ edit2.Text：= TCaption（key）;”行上放置断点我可以看到ShortString“ key”确实已经正确加密，但是后面还包含许多奇怪的字符。
前16个字符是真正的加密。
encryption http://img831.imageshack.us/img831/365/29944312.png
bigger version: http://img831.imageshack.us/img831/365/29944312.png
谢谢！
最佳答案
代码做什么
对于那些不讲汇编程序的人，这可能是Pascal中应该执行的代码。之所以“可能”是因为原始版本包含一些错误：
procedure TForm14.Button1Click(Sender: TObject);
var KeyLen:Integer;
Name, Key:ShortString;
i:Integer;
CurrentKeyByte:Byte;
CurrentNameByte:Byte;
begin
Name := ShortString(Edit1.Text);
Key := '_r <()<1-Z2[l5,^';
keyLen := Length(key);
asm int 3 end; // This is here so I can inspect the assembler output in the IDE
// for the "Optimised" version of the code
for i:=1 to Length(Name) do
begin
CurrentKeyByte := Byte(Key[i mod KeyLen]);
CurrentNameByte := Byte(Name[i]);
CurrentNameByte := ((CurrentKeyByte xor CurrentNameByte) mod $019) + $041;
Name[i] := AnsiChar(CurrentNameByte);
end;
Caption := Name;
end;
启用优化后，由此生成的汇编代码实际上比建议的代码短，不包含冗余代码，我敢打赌它会更快。我在Delphi生成的代码中注意到了一些优化（与OP提出的汇编代码相比）：
Delphi反转了循环（降至0）。这样可以节省一条“ CMP”指令，因为编译器可以简单地“ DEC ESI”并在零标志上循环。
第二部分使用了“ XOR EDX”和“ DIV EBX”，从而节省了很少的周期。
为什么提供的汇编代码失败？
这是原始的汇编代码，带有注释。该错误位于例程末尾的“ CMP”指令中-它将ESI与KEY的长度而不是NAME的长度进行比较。如果KEY的长度比NAME长，则“加密”会继续覆盖NAME，从而覆盖内容（被覆盖的内容是字符串的NULL终止符，导致调试器在正确的字符后显示有趣的字符）。
虽然不允许覆盖EBX和ESI，但这不是导致代码出现AV的原因，可能是因为周围的Delphi代码未使用EBX或ESI（只是尝试了此操作）。
asm
XOR EAX,EAX ; Wasteful, the first instruction in Loop overwrites EAX
XOR ESI,ESI
XOR EDX,EDX ; Wasteful, the first CDQ instruction in Loop overwrites EDX
XOR ECX,ECX ; Wasteful, the first LEA instruction overwrites ECX
@loopBegin:
; Etering the loop, ESI holds the index for the next char to be
; encrypted.
MOV EAX,ESI ; Load EAX with the index for the next char, because
; we intend to do some divisions (setting up the call to IDIV)
PUSH $019 ; ? pushing this here, so we can pop it 3 lines later... obfuscation
CDQ ; Sign-extend EAX (required for IDIV)
IDIV DWORD PTR DS:[serialLen] ; Divide EAX by the length of the key.
MOV EAX,ESI ; Load the index back to EAX, we're planning on an other IDIV. Why???
POP EBX ; Remember the PUSH $019?
LEA ECX,DWORD PTR DS:[key+EDX] ; EDX is the result of "ESI mod serialLen", this
; loads the address of the current char in the
; encryption key into ECX. Dividing by serialLen
; is supposed to make sure we "wrap around" at the
; end of the key
CDQ ; Yet some more obfuscation. We're now extending EAX into EDX in preparation for IDIV.
; This is obfuscation becasue the "MOV EAX, ESI" instruction could be written right here
; before the CDQ.
IDIV DWORD PTR DS:[nameLen] ; We divide the current index by the length of the text
; to be encrypted. Once more the code will only use the reminder,
; but why would one do this? Isn't ESI (the index) always supposed to
; be LESS THEN nameLen? This is the first sign of trouble.
LEA EAX,DWORD PTR DS:[name] ; EAX now holds the address of NAME.
MOVZX EAX,BYTE PTR DS:[name+EDX] ; EAX holds the current character in name
MOVZX EDX,BYTE PTR DS:[ECX] ; EDX holds the current character in Key
XOR EAX,EDX ; Aha!!!! So this is an obfuscated XOR loop! EAX holds the "name[ESI] xor key[ESI]"
CDQ ; We're extending EAX (the XOR result) in preparation for a divide
IDIV EBX ; Divde by EAX by EBX (EBX = $019). Why????
ADD DL,$041 ; EDX now holds the remainder of our previous XOR, after the division by $019;
; This is an number from $000 to $018. Adding $041 turns it into an number from
; $041 to $05A (ASCII chars from "A" to "Z"). Now I get it. This is not encryption,
; this is a HASH function! One can't un-encrypt this (information is thrown away at
; the division).
INC ESI ; Prep for the next char
; !!! BUG !!!
;
; This is what's causing the algorithm to generate the AV. At this step the code is
; comparing ESI (the current char index) to the length of the KEY and loops back if
; "ESI < serialLen". If NAME is shorter then KEY, encryption will encrypt stuff beyond
; then end of NAME (up to the length of KEY). If NAME is longer then KEY, only Length(Key)
; bytes would be encrypted and the rest of "Name" would be ignored.
;
CMP ESI,DWORD PTR DS:[serialLen]
MOV BYTE PTR DS:[ECX],DL ; Obfuscation again. This is where the mangled char is written
; back to "Name".
JL @loopBegin ; Repeat the loop.
我的2美分建议
汇编程序应用于SPEED优化，而别无其他。在我看来，好像OP试图使用Assembler来混淆代码在做什么。没有帮助，我只花了几分钟就弄清楚了代码在做什么，而且我不是汇编专家。