屏幕录像专家 V3.0 算法分析 -pc6资讯

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屏幕录像专家 V3.0 算法分析 时间：2004/10/15 0:55:00来源：本站整理作者：蓝点我要评论(0): 　

软件下载： http://www.tlxsoft.com/
破解工具：SoftICE
破解时间：2003-4-8
***********************************************************************************************

　　你一定可以来到这里…… ^_^

:0041B862 8D45F8 lea eax, dword ptr [ebp-08]
:0041B865 E8B68FFEFF call 00404820
:0041B86A 50 push eax
:0041B86B 8D9580FBFFFF lea edx, dword ptr [ebp+FFFFFB80]
:0041B871 52 push edx
:0041B872 E84D0C0700 call 0048C4C4
:0041B877 83C408 add esp, 00000008
:0041B87A FF4DBC dec [ebp-44]
:0041B87D 8D45F8 lea eax, dword ptr [ebp-08]
:0041B880 BA02000000 mov edx, 00000002
:0041B885 E886C00700 call 00497910
:0041B88A 8D8D80FBFFFF lea ecx, dword ptr [ebp+FFFFFB80]
:0041B890 51 push ecx
:0041B891 E85E0C0700 call 0048C4F4
:0041B896 59 pop ecx
:0041B897 89458C mov dword ptr [ebp-74], eax
:0041B89A C745889CFFFFFF mov [ebp-78], FFFFFF9C //[ebp-78]=0xFFFFFF9C
:0041B8A1 33C0 xor eax, eax
:0041B8A3 894590 mov dword ptr [ebp-70], eax
:0041B8A6 8B5590 mov edx, dword ptr [ebp-70]
:0041B8A9 3B558C cmp edx, dword ptr [ebp-74]
:0041B8AC 7D20 jge 0041B8CE

* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0041B8CC(C)
|
:0041B8AE 8B4D90 mov ecx, dword ptr [ebp-70]
:0041B8B1 8A840D80FBFFFF mov al, byte ptr [ebp+ecx-00000480]
:0041B8B8 884597 mov byte ptr [ebp-69], al
:0041B8BB 33D2 xor edx, edx
:0041B8BD 8A5597 mov dl, byte ptr [ebp-69]
:0041B8C0 015588 add dword ptr [ebp-78], edx //0xFFFFFF9C 与用户名每个字符累加求和
:0041B8C3 FF4590 inc [ebp-70]
:0041B8C6 8B4D90 mov ecx, dword ptr [ebp-70]
:0041B8C9 3B4D8C cmp ecx, dword ptr [ebp-74]
:0041B8CC 7CE0 jl 0041B8AE

* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0041B8AC(C)
|
:0041B8CE 8B4588 mov eax, dword ptr [ebp-78]
:0041B8D1 898578F7FFFF mov dword ptr [ebp+FFFFF778], eax
:0041B8D7 33D2 xor edx, edx
:0041B8D9 89957CF7FFFF mov dword ptr [ebp+FFFFF77C], edx
:0041B8DF DFAD78F7FFFF fild qword ptr [ebp+FFFFF778] //累加和结果送 st(0)
:0041B8E5 DB2D5CBD4100 fld tbyte ptr [0041BD5C] //st(1)=0.6480041472265422897
:0041B8EB DEC9 fmulp st(1), st(0) //st(1)=st(0)*st(1)
:0041B8ED D80568BD4100 fadd dword ptr [0041BD68] //加上1233.99999999999999957
:0041B8F3 E8F84F0700 call 004908F0 //取结果的整数
:0041B8F8 894588 mov dword ptr [ebp-78], eax
:0041B8FB 8B5588 mov edx, dword ptr [ebp-78]
:0041B8FE 899578F7FFFF mov dword ptr [ebp+FFFFF778], edx
:0041B904 33C9 xor ecx, ecx
:0041B906 898D7CF7FFFF mov dword ptr [ebp+FFFFF77C], ecx
:0041B90C DFAD78F7FFFF fild qword ptr [ebp+FFFFF778]
:0041B912 DC0D6CBD4100 fmul qword ptr [0041BD6C]
//上面的整数*3121.14159259999996697388632872504
:0041B918 E8D34F0700 call 004908F0 //取结果的整数
:0041B91D 894588 mov dword ptr [ebp-78], eax //保存到[ebp-78]
:0041B920 66C745B02C00 mov [ebp-50], 002C
:0041B926 8D45F4 lea eax, dword ptr [ebp-0C]
:0041B929 E8065EFEFF call 00401734
:0041B92E 8BD0 mov edx, eax
:0041B930 FF45BC inc [ebp-44]
:0041B933 8B4D9C mov ecx, dword ptr [ebp-64]
:0041B936 8B81E4020000 mov eax, dword ptr [ecx+000002E4]
:0041B93C E84B150400 call 0045CE8C
:0041B941 8D45F4 lea eax, dword ptr [ebp-0C]
:0041B944 E8D78EFEFF call 00404820
:0041B949 50 push eax
:0041B94A 8D9580FBFFFF lea edx, dword ptr [ebp+FFFFFB80]
:0041B950 52 push edx
:0041B951 E86E0B0700 call 0048C4C4
:0041B956 83C408 add esp, 00000008
:0041B959 FF4DBC dec [ebp-44]
:0041B95C 8D45F4 lea eax, dword ptr [ebp-0C]
:0041B95F BA02000000 mov edx, 00000002
:0041B964 E8A7BF0700 call 00497910
:0041B969 8D8D80FBFFFF lea ecx, dword ptr [ebp+FFFFFB80]
:0041B96F 51 push ecx
:0041B970 E87F0B0700 call 0048C4F4
:0041B975 59 pop ecx
:0041B976 89458C mov dword ptr [ebp-74], eax
:0041B979 33C0 xor eax, eax
:0041B97B 894590 mov dword ptr [ebp-70], eax //[ebp-70]=eax=0
:0041B97E 8B5590 mov edx, dword ptr [ebp-70]
:0041B981 3B558C cmp edx, dword ptr [ebp-74]
:0041B984 7D46 jge 0041B9CC

* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0041B9CA(C)
|
:0041B986 8B4590 mov eax, dword ptr [ebp-70] //[ebp-70]依次等于 0,1,2,3...
:0041B989 B903000000 mov ecx, 00000003
:0041B98E 99 cdq
:0041B98F F7F9 idiv ecx //[ebp-70]/3，商送 al
:0041B991 8B5590 mov edx, dword ptr [ebp-70]
:0041B994 8A8C1580FBFFFF mov cl, byte ptr [ebp+edx-00000480] //依次取注册码各个字符
:0041B99B 80C1EC add cl, EC //字符+0xFFFFFFEC
:0041B99E 8B5590 mov edx, dword ptr [ebp-70] //[ebp-70]=edx
:0041B9A1 81E201000080 and edx, 80000001 //取奇数位字符则edx=0，取偶数位字符则edx=1
:0041B9A7 7905 jns 0041B9AE
:0041B9A9 4A dec edx
:0041B9AA 83CAFE or edx, FFFFFFFE
:0041B9AD 42 inc edx

* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0041B9A7(C)
|
:0041B9AE 03D2 add edx, edx
:0041B9B0 8D1492 lea edx, dword ptr [edx+4*edx] //奇数位字符则dl=0，偶数位字符则 dl=0xA
:0041B9B3 2ACA sub cl, dl //cl=cl-dl（即计算奇数位字符时-0,计算偶数位字符时-0xA）
:0041B9B5 02C1 add al, cl //al=al+cl（al 就是[ebp-70]/3的商）
:0041B9B7 8B4D90 mov ecx, dword ptr [ebp-70]
:0041B9BA 88840D80FBFFFF mov byte ptr [ebp+ecx-00000480], al
:0041B9C1 FF4590 inc [ebp-70] //[ebp-70]递增1
:0041B9C4 8B4590 mov eax, dword ptr [ebp-70]
:0041B9C7 3B458C cmp eax, dword ptr [ebp-74]
:0041B9CA 7CBA jl 0041B986 //循环并分别用注册码各个字符计算出一串数值

* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:0041B984(C)
|
:0041B9CC 8D8580FBFFFF lea eax, dword ptr [ebp+FFFFFB80]
:0041B9D2 50 push eax
:0041B9D3 8D9580F7FFFF lea edx, dword ptr [ebp+FFFFF780]
:0041B9D9 52 push edx
:0041B9DA E8E50A0700 call 0048C4C4
:0041B9DF 83C408 add esp, 00000008
:0041B9E2 66C745B03800 mov [ebp-50], 0038
:0041B9E8 8D9580F7FFFF lea edx, dword ptr [ebp+FFFFF780]
:0041B9EE 8D45F0 lea eax, dword ptr [ebp-10]
:0041B9F1 E8B2BD0700 call 004977A8
:0041B9F6 8BD0 mov edx, eax
:0041B9F8 FF45BC inc [ebp-44]
:0041B9FB 8D45FC lea eax, dword ptr [ebp-04]
:0041B9FE E83DBF0700 call 00497940
:0041BA03 FF4DBC dec [ebp-44]
:0041BA06 8D45F0 lea eax, dword ptr [ebp-10]
:0041BA09 BA02000000 mov edx, 00000002
:0041BA0E E8FDBE0700 call 00497910
:0041BA13 8D45FC lea eax, dword ptr [ebp-04]
:0041BA16 E8F5C00700 call 00497B10 //验证注册码的“合法性”并计算出一个值送 eax ，跟入……

　　从0041BA16 → 00497B38 → 00482057，来到……

:0048903C 53 push ebx
:0048903D 56 push esi
:0048903E 57 push edi
:0048903F 89C6 mov esi, eax
:00489041 50 push eax
:00489042 85C0 test eax, eax
:00489044 7473 je 004890B9
:00489046 31C0 xor eax, eax
:00489048 31DB xor ebx, ebx
:0048904A BFCCCCCC0C mov edi, 0CCCCCCC

下面是逐个验证注册码各个字符计算出的数值的“合法性”，实际上间接验证了输入注册码的“合法性”。

* Referenced by a (U)nconditional or (C)onditional Jump at Address:
|:00489055(C)
|
:0048904F 8A1E mov bl, byte ptr [esi]
:00489051 46 inc esi
:00489052 80FB20 cmp bl, 20
:00489055 74F8 je 0048904F
:00489057 B500 mov ch, 00
:00489059 80FB2D cmp bl, 2D
:0048905C 7469 je 004890C7
:0048905E 80FB2B cmp bl, 2B
:00489061 7466 je 004890C9
:00489063 80FB24 cmp bl, 24
:00489066 7466 je 004890CE
:00489068 80FB78 cmp bl, 78
:0048906B 7461 je 004890CE
:0048906D 80FB58 cmp bl, 58
:00489070 745C je 004890CE
:00489072 80FB30 cmp bl, 30
:00489075 7513 jne 0048908A
:00489077 8A1E mov bl, byte ptr [esi]
:00489079 46 inc esi
:0048907A 80FB78 cmp bl, 78
:0048907D 744F je 004890CE
:0048907F 80FB58 cmp bl, 58
:00489082 744A je 004890CE
:00489084 84DB test bl, bl
:00489086 7420 je 004890A8
:00489088 EB04 jmp 0048908E

* Referenced by a (U)nconditional or (C)onditional Jump at Addresses:
|:00489075(C), :004890CC(U)
|
:0048908A 84DB test bl, bl
:0048908C 7434 je 004890C2

* Referenced by a (U)nconditional or (C)onditional Jump at Addresses:
|:00489088(U), :004890A6(C)
|
:0048908E 80EB30 sub bl, 30
:00489091 80FB09 cmp bl, 09 //关键，从中我们可以推算出各位注册码的取值范围
:00489094 772C ja 004890C2 //跳？？？不要！！！
:00489096 39F8 cmp eax, edi
:00489098 7728 ja 004890C2
:0048909A 8D0480 lea eax, dword ptr [eax+4*eax]
:0048909D 01C0 add eax, eax
:0048909F 01D8 add eax, ebx //每次 "bl-30" 的值组成串再转换成数值
:004890A1 8A1E mov bl, byte ptr [esi]
:004890A3 46 inc esi
:004890A4 84DB test bl, bl
:004890A6 75E6 jne 0048908E

　　计算完毕，回到……

:0041BA1B B97C000000 mov ecx, 0000007C
:0041BA20 99 cdq
:0041BA21 F7F9 idiv ecx
:0041BA23 83C064 add eax, 00000064
:0041BA26 894584 mov dword ptr [ebp-7C], eax
:0041BA29 8B4584 mov eax, dword ptr [ebp-7C] //eax=eax/0x7C+0x64
:0041BA2C 2B4588 sub eax, dword ptr [ebp-78] //eax-用户名计算出的值
:0041BA2F 83F864 cmp eax, 00000064　　　　　　 //等于 0x64 则注册成功
:0041BA32 0F85BC020000 jne 0041BCF4

****************************

　　实例分析：
　　以用户名 PaulYoung 为例，

用户名计算：
0xFFFFFF9C+0x50+0x61+0x75+0x6C+0x59+0x6F0x75+0x6E+0x67=0x340=832
832*0.6480041472265422897+1233.99999999999999957结果的整数为1773
1773*3121.14159259999996697388632872504结果的整数为0x547058

注册码计算：
假设某位注册码字符为 S ，则
奇数位计算：S+0xFFFFFFEC+(x/3 的商) （x 依次等于0,1,2,3...）
偶数位计算：S+0xFFFFFFEC-0xA+(x/3 的商)

而从
:0048908E 80EB30 sub bl, 30
:00489091 80FB09 cmp bl, 09
:00489094 772C ja 004890C2

我们可以看到，奇数位及偶数位注册码取值范围分别是：
奇数位范围：0x30≤S+0xFFFFFFEC+(x/3)≤0x39
偶数位范围：0x30≤S+0xFFFFFFEC-0xA+(x/3)≤0x39
由此我们可以推算出注册码的“合法”取值范围，分别是：
第一位：D,E,F,G,H,I,J,K,L,M
第二位：N,O,P,Q,R,S,T,U,V,W
第三位：D,E,F,G,H,I,J,K,L,M
第四位：M,N,O,P,Q,R,S,T,U,V
第五位：C,D,E,F,G,H,I,J,K,L
第六位：M,N,O,P,Q,R,S,T,U,V
第七位：B,C,D,E,F,G,H,I,J,K
第八位：L,M,N,O,P,Q,R,S,T,U
第九位：B,C,D,E,F,G,H,I,J,K
...

注册码计算出的值假设为 N ，(N/0x7C的商)+0x64-用户名计算出的值=0x64 ，满足条件则注册成功。
用 PaulYoung 计算出的值为 0x547058，则用 0x547058*0x7C 可以算出N=686189216 (DEC)
而686189216中每位数字实际是0048908E中算出的 bl 的值。
因此，我们可以逆推出注册码各个字符，如第一位注册码（假设为S），即
S+0xFFFFFFEC+0/3-0x30=6 ，则 S=0x4A='J'

也可这样理解，如第一位注册码：
0,1,2,3,4,5,6,7,8,9　对应
D,E,F,G,H,I,J,K,L,M

是6则取对应的J，其它同理……

依此类推，算出一个可用的注册码
Name:PaulYoung
Code:JVJNKVDMH
或
Name:CCG
Code:INGVCOBNF

　　另外，N/0x7C 只用到它的商，不同的 N 值都可以算出同样的商，因此，同一用户名其实可以有很多个可用的注册码。
____________________________________________________________________________________________

　　很久很久没玩破解了，基于个性的懒惰，分析可能并不全面，如有发现，请跟帖批评指正。希望我粗糙的文笔及蹩脚的表达能力不会令大家望而生厌…… :-)

PaulYoung
属于中国破解组织CCG(CHiNA CrACKiNG GrOUp)

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