算法难的不会搞，只能拿简单的来试手了:-),也算是开始学用IDA分析东西了
【目     标】:diablo2002’s crackme1
【工     具】:IDA 4.7 
【任     务】:算法分析 
【操作平台】:Windows 2003 server 
【作     者】: LOVEBOOM[DFCG][FCG][US]
【相关链接】: 附件
【简要说明】： 一个非常简单的CrackMe入门级的，以前没有试过用ida分析东西，今天开始试着用IDA分析。
【详细过程】:
该CRACKME是masm32写的，所以非常直观的找到关键处,直接静态分析就可以写出注册机的,分析如下：
.text:00401227                 jnz     loc_4013BB
.text:0040122D                 mov     eax, [ebp+wParam]         ; Case EAX==WM_COMMAND
.text:00401230                 cmp     ax, 3
.text:00401234                 jnz     loc_4013D0
.text:0040123A                 shr     eax, 10h
.text:0040123D                 or      ax, ax
.text:00401240                 jnz     loc_4013B9
.text:00401246                 xor     eax, eax                  ; 准备获取用户名
.text:00401248                 push    28h                       ; nMaxCount
.text:0040124A                 push    offset name_szBuffer      ; lpString
.text:0040124F                 push    2                         ; nIDDlgItem
.text:00401251                 push    [ebp+hWnd]                ; hDlg
.text:00401254                 call    GetDlgItemTextA
.text:00401259                 test    al, al
.text:0040125B                 jz      Name_isEmpty              ; 比较用户名是长是否为0
.text:00401261                 cmp     al, 20h                   ; 用户名长度是否大于20H
.text:00401263                 jg      Name_ToLong
.text:00401269                 cmp     al, 5                     ; 比较用户名长度是否小于5
.text:0040126B                 jl      Name_IsToShort
.text:00401271                 lea     ebx, ds:40318Ch           ; 取出保存用户名的地址到EBX中
.text:00401277                 xor     ecx, ecx
.text:00401279                 mov     al, 5                     ; 开始计算KEY1
.text:0040127B                 xor     edx, edx                  ; EDX清0
.text:0040127D
.text:0040127D Loop_Key1:                                        ; CODE XREF: sub_401109+19B j
.text:0040127D                 mov     cl, [edx+ebx]             ; 取出用户名的每一位
.text:00401280                 xor     cl, 29h                   ; KEY=用户名xor 29h
.text:00401283                 add     cl, al                    ; KEY=Key add len(UerName)
.text:00401285                 cmp     cl, 41h                   ; 如果相加后的KEY小于41h,则key=52H,key=key add len(userName)
.text:00401288                 jl      short Mov_CL_52h
.text:0040128A                 cmp     cl, 5Ah                   ; 如果相加后的KEY大于5Ah,则key=52H,key=key add len(userName)
.text:0040128D                 jg      short Mov_CL_52h
.text:0040128F
.text:0040128F loc_40128F:                                       ; CODE XREF: sub_401109+1A1 j
.text:0040128F                 mov     SaveKey1[edx], cl         ; 计算后的值保存在40313C处
.text:00401295                 mov     byte_40313D[edx], 0
.text:0040129C                 inc     dl
.text:0040129E                 dec     al
.text:004012A0                 cmp     al, 0
.text:004012A2                 jz      short jmp_next            ; 开始计算KEY2
.text:004012A4                 jmp     short Loop_Key1
.text:004012A6 ; ----------------------------------------------------------------------------
.text:004012A6
.text:004012A6 Mov_CL_52h:                                       ; CODE XREF: sub_401109+17F j
.text:004012A6                                                   ; sub_401109+184 j
.text:004012A6                 mov     cl, 52h
.text:004012A8                 add     cl, al
.text:004012AA                 jmp     short loc_40128F          ; 计算后的值保存在40313C处
.text:004012AC ; ----------------------------------------------------------------------------
.text:004012AC
.text:004012AC jmp_next:                                         ; CODE XREF: sub_401109+199 j
.text:004012AC                 xor     edx, edx                  ; 开始计算KEY2
.text:004012AE                 mov     eax, 5
.text:004012B3
.text:004012B3 Loop_key2:                                        ; CODE XREF: sub_401109+1D4 j
.text:004012B3                 mov     cl, [edx+ebx]             ; 取出用户名的每一位tmpkey=asc(mid(username,i,1)
.text:004012B6                 xor     cl, 27h                   ; tmpkey=tmpkey xor &H27
.text:004012B9                 add     cl, al                    ; tmpkey=tmpkey add loopval(al)
.text:004012BB                 add     cl, 1                     ; tmpkey=tmpkey+1
.text:004012BE                 cmp     cl, 41h                   ; if tmpkey<&H41 then tmpkey=&H4D add loopval
.text:004012C1                 jl      short Mov_CL_4DH
.text:004012C3                 cmp     cl, 5Ah
.text:004012C6                 jg      short Mov_CL_4DH          ; if tmpkey >&H5A then tmpkey=&H4D add loopval
.text:004012C8
.text:004012C8 loc_4012C8:                                       ; CODE XREF: sub_401109+1DA j
.text:004012C8                 mov     SaveKey2[edx], cl
.text:004012CE                 mov     byte_403142[edx], 0
.text:004012D5                 inc     dl
.text:004012D7                 dec     al
.text:004012D9                 cmp     al, 0
.text:004012DB                 jz      short Jmp_next1           ; 准备获取注册码
.text:004012DD                 jmp     short Loop_key2           ; 取出用户名的每一位tmpkey=asc(mid(username,i,1)
.text:004012DF ; ----------------------------------------------------------------------------
.text:004012DF
.text:004012DF Mov_CL_4DH:                                       ; CODE XREF: sub_401109+1B8 j
.text:004012DF                                                   ; sub_401109+1BD j
.text:004012DF                 mov     cl, 4Dh
.text:004012E1                 add     cl, al
.text:004012E3                 jmp     short loc_4012C8
.text:004012E5 ; ----------------------------------------------------------------------------
.text:004012E5
.text:004012E5 Jmp_next1:                                        ; CODE XREF: sub_401109+1D2 j
.text:004012E5                 xor     eax, eax                  ; 准备获取注册码
.text:004012E7                 push    28h                       ; nMaxCount
.text:004012E9                 push    offset Key_szBuffer       ; lpString
.text:004012EE                 push    4                         ; nIDDlgItem
.text:004012F0                 push    [ebp+hWnd]                ; hDlg
.text:004012F3                 call    GetDlgItemTextA
.text:004012F8                 test    ax, ax
.text:004012FB                 jz      short Invalid_Key         ; 如果注册码为空则OVER
.text:004012FD                 cmp     ax, 0Ah
.text:00401301                 jg      short Invalid_Key         ; 如果注册码长度不为10则over
.text:00401303                 jl      short Invalid_Key
.text:00401305                 xor     eax, eax
.text:00401307                 xor     ebx, ebx
.text:00401309                 xor     ecx, ecx
.text:0040130B                 xor     edx, edx
.text:0040130D                 lea     eax, ds:4031B4h
.text:00401313
.text:00401313 loop_compareKey:                                  ; CODE XREF: sub_401109+234 j
.text:00401313                 mov     bl, [ecx+eax]
.text:00401316                 mov     dl, SaveKey1[ecx]
.text:0040131C                 cmp     bl, 0
.text:0040131F                 jz      Correct_Key
.text:00401325                 add     dl, 5                     ; 再次取计算后的KEY，如果值+5大于5A的话，值-0D
.text:00401328                 cmp     dl, 5Ah
.text:0040132B                 jg      short Sub_DL_0D
.text:0040132D
.text:0040132D loc_40132D:                                       ; CODE XREF: sub_401109+23B j
.text:0040132D                 xor     dl, 0Ch                   ; if key<&H41 then key=&H4B +loopVal
.text:00401330                 cmp     dl, 41h
.text:00401333                 jl      short ADDMOV_DL_4B
.text:00401335                 cmp     dl, 5Ah                   ; if Key>&H5A then key=&h4B - LoopVal
.text:00401338                 jg      short subMov_dl_4b
.text:0040133A
.text:0040133A loc_40133A:                                       ; CODE XREF: sub_401109+241 j
.text:0040133A                                                   ; sub_401109+247 j
.text:0040133A                 inc     ecx
.text:0040133B                 cmp     dl, bl                    ; 如果结果不相等则OVER
.text:0040133D                 jz      short loop_compareKey
.text:0040133F                 jmp     short Invalid_Key
.text:00401341 ; ----------------------------------------------------------------------------
.text:00401341
.text:00401341 Sub_DL_0D:                                        ; CODE XREF: sub_401109+222 j
.text:00401341                 sub     dl, 0Dh
.text:00401344                 jmp     short loc_40132D          ; if key<&H41 then key=&H4B +loopVal
.text:00401346 ; ----------------------------------------------------------------------------
.text:00401346
.text:00401346 ADDMOV_DL_4B:                                     ; CODE XREF: sub_401109+22A j
.text:00401346                 mov     dl, 4Bh
.text:00401348                 add     dl, cl
.text:0040134A                 jmp     short loc_40133A
.text:0040134C ; ----------------------------------------------------------------------------
.text:0040134C
.text:0040134C subMov_dl_4b:                                     ; CODE XREF: sub_401109+22F j
.text:0040134C                 mov     dl, 4Bh
.text:0040134E                 sub     dl, cl
.text:00401350                 jmp     short loc_40133A
.text:00401352 ; ----------------------------------------------------------------------------
.text:00401352
.text:00401352 Invalid_Key:                                      ; CODE XREF: sub_401109+1F2 j
.text:00401352                                                   ; sub_401109+1F8 j ...
.text:00401352                 push    0                         ; uType
.text:00401354                 push    offset Caption            ; lpCaption
.text:00401359                 push    offset Text               ; lpText
.text:0040135E                 push    0                         ; hWnd
.text:00401360                 call    MessageBoxA
.text:00401365                 jmp     short loc_4013B9
.text:00401367 ; ----------------------------------------------------------------------------
.text:00401367
.text:00401367 Name_isEmpty:                                     ; CODE XREF: sub_401109+152 j
.text:00401367                 push    0                         ; uType
.text:00401369                 push    offset aSorry___          ; lpCaption
.text:0040136E                 push    offset aEnterName_0       ; lpText
.text:00401373                 push    0                         ; hWnd
.text:00401375                 call    MessageBoxA
.text:0040137A                 jmp     short loc_4013B9
.text:0040137C ; ----------------------------------------------------------------------------
.text:0040137C
.text:0040137C Name_ToLong:                                      ; CODE XREF: sub_401109+15A j
.text:0040137C                 push    0                         ; uType
.text:0040137E                 push    offset aSorry___          ; lpCaption
.text:00401383                 push    offset aNameCanBeMax32    ; lpText
.text:00401388                 push    0                         ; hWnd
.text:0040138A                 call    MessageBoxA
.text:0040138F                 jmp     short loc_4013B9
.text:00401391 ; ----------------------------------------------------------------------------
.text:00401391
.text:00401391 Name_IsToShort:                                   ; CODE XREF: sub_401109+162 j
.text:00401391                 push    0                         ; uType
.text:00401393                 push    offset aSorry___          ; lpCaption
.text:00401398                 push    offset aNameMustBeMin5    ; lpText
.text:0040139D                 push    0                         ; hWnd
.text:0040139F                 call    MessageBoxA
.text:004013A4                 jmp     short loc_4013B9
.text:004013A6 ; ----------------------------------------------------------------------------
.text:004013A6
.text:004013A6 Correct_Key:                                      ; CODE XREF: sub_401109+216 j
.text:004013A6                 push    0                         ; uType
.text:004013A8                 push    offset aGoodCracker       ; lpCaption
.text:004013AD                 push    offset aSerialIsCorrec    ; lpText
.text:004013B2                 push    0                         ; hWnd
.text:004013B4                 call    MessageBoxA
.text:004013B9
.text:004013B9 loc_4013B9:                                       ; CODE XREF: sub_401109+137 j
.text:004013B9                                                   ; sub_401109+25C j ...
.text:004013B9                 jmp     short loc_4013D0
 

总结一下算法为：
只用注册名的前五位参与运算。共分为三个部分
第一部分：
count1=5
取用户名的每一位nameval1
nameval1 异或29h加上循环值count1
运算后的值小于41h或大于5ah则nameval1=52h + count1
count1-1,直到count1为0结束第一部分key1

第二部分：
count2=5
取用户名的每一位nameval2
nameval2异或27加上循环值加上1
运算后的值如果小于41h或大于5ah则nameval2=4dh+count2
count2=count2-1直到count2为0结束第二部分key2

第三部分：
count3=0
tmpkey=key1+key2
取tmpkey的每一位keyval
keyval加上5
运算后的值如果大于5ah则keyval=keyval-0d
keyval异或0ch
如果异或后的值小于41则keyval=4b加上count3
如果异或后的值大于5ah则keyval=4bh减去count3
循环10次，得出正确注册码。
附件里有asm和　VB版的注册机J

Greetz:
 Fly.Jingulong,yock,tDasm.David.hexer,hmimys,ahao.UFO(brother).alan(sister).all of my friends and you!

                        By loveboom[DFCG][FCG][US]
                        http://blog.csdn.net/bmd2chen
                        Email:loveboom#163.com
                        Date:2005-6-12 13:49

附:VB+asm注册机源码:-)
附件:cr1kg.rar

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