Any one see this Cryptographic?

Originally Posted by winndy

It should be symmetrical cipher .
cipher(username)=Registrationcode

Actually you are not right This is asymmetric crypto

These three calls look like BigCreate or smth like that:

.text:0041C2ED                 call    sub_401974
....
.text:0041C300                 call    sub_401974
....
.text:0041C317                 call    sub_401974

and for the third call you have this parameter

push    10001h

This is typical value for public exponent (E) for RSA cryptosystem.



on this line

0041C289   . E8 E8280100    CALL <JMP.&MFC42.#537>

in esp+60 you have:

0012CDF4  6B 04 49 CD CB 80 9A 82  kI����Ђљ‚
0012CDFC  C0 57 51 3F 84 63 0C B5  ��WQ?„c.µ
0012CE04  50 D5 56 AA 71 DF 5A B0  P��VЄq��Z��
0012CE0C  D4 3C 2E 7B C3 9A B6 CF  ��<.{��љ&para;��

6B 04 49 CD CB 80 9A 82 C0 57 51 3F 84 63 0C B5 50 D5 56 AA 71 DF 5A B0 D4 3C 2E 7B C3 9A B6 CF

if we remove spaces we get this:

6B0449CDCB809A82C057513F84630CB550D556AA71DF5AB0D43C2E7BC39AB6CF

Now paste it in RSA Tool in Modulus (N) field and push 'Reverse'. Now you've got public key:

CFB69AC37B2E3CD4B05ADF71AA56D550B50C63843F5157C0829A80CBCD49046B

To create keygen you have to find factors (find p and q that p*q=N). For this needs you can use RSA Tool, but when you have modulus > 200 bits (in your case you have 256 bits) RSA Tool is too slow. So you should better use tools by Satoshi Tomabechi.

You can get these tools here:

http://www.asahi-net.or.jp/~KC2H-MSM/cn/

When you get p and q you can calculate D.

When you have N & D you can code keygen