Simple .NET keygenme

[GIV]

Hi guys.

Today i have made a small keygenme.

The algo is very simple (getting to the algo is not).

Difficulty : 4
Language : .NET
Platform : Windows X86/X64
OS Version : XP and above
Packer / Protector : Eazfuscator

Description :

Simple keygenme with short computing algo.

 

Simple Keygenme 2016 - giv.rar

[Ahmad_k]

Stuck on deobfuscating EazFuscator.

i tried eazdevirt with de4dot still no luck. so i have to change the source code of de4dot to support newer version of this obfuscator 

[Insid3Code]

Spoiler

Insid3Code
731101151051005167111100101

Nice work GIV

Fishing the serial for fun!

[GIV]

10 hours ago, Ahmad_k said:

Stuck on deobfuscating EazFuscator.

i tried eazdevirt with de4dot still no luck. so i have to change the source code of de4dot to support newer version of this obfuscator 

We wait for your modded de4dot.

[Ahmad_k]

i hope i can do it

[GIV]

Fingers crossed.

[RDGMax]

How is noticed the correct Message?

[GIV]

Yes the smiley is the correct serial message.

Maybe i will change the algo a little bit in a new build.

Edited August 5, 2016 by GIV

[Ahmad_k]

any clue on deobfuscating ? 

[GIV]

Devirtualize the Eazfuscator VM.

[kao]

Sure, you can spend few days making a devirtualizer. Or you can take Olly or x64dbg and debug JITed x86 code instead. That's what I did. :-)

[GIV]

This method is reliable in large code functions/programs?

[GIV]

Here is a small modification.

Can you keygen this? Algo is not complicated either.

 

Simple Keygenme 2016 - giv.rar

[kao]

I'm "out of office" until Sunday night but I'll be happy to try it on Monday..

[Insid3Code]

2 hours ago, GIV said:

Here is a small modification.

Can you keygen this? Algo is not complicated either.

 

Simple Keygenme 2016 - giv.rar

Spoiler

%Insid3Code
37731101151051005167111100101giv

[RDGMax]

hmmmm .net

 security  -10

[GIV]

3 hours ago, Insid3Code said:

  Reveal hidden contents

%Insid3Code
37731101151051005167111100101giv

Write a keygen.

[Insid3Code]

Quote

Write a keygen.

Attached binary with source, it's only conversion (ASCII/Decimal) with an trick!

keygen.rar

[Ahmad_k]

Trying again with eazdevirt tool. it crashes.

After debugging i found that newer version of eazfuscator uses Dup instead of Ldloc.0 as first instruction in the dictionary. so after changing this now eazdevirt can run. But now i got 0 methods devirtualized . 

On old challenge (Jan 2016) @Saneki noticed a change in VM's stream type and he updated eazdevirt source code but didn't release the new updated source.

 

[GIV]

On 06.08.2016 at 4:00 AM, Insid3Code said:

Attached binary with source, it's only conversion (ASCII/Decimal) with an trick!

keygen.rar

Hi.

You hardcoded a string before the name.

Is a combination but the options are more than this hardcoded string.

The original code was:

If txtKey.Text.ToString.Substring(0, 1) = "3" And txtKey.Text.ToString.Substring(2, 1) = "7" Then
                  txtKey.Text = ""
                  txtKey.Enabled = False
                    txtKey.Text = ":))"
                End If

So first and third character from the serial which is the ASCII correspondent of the name characters must begin with 3 and 7.

In this way if we look at the ASCII table the possibilities are much more that the hardcoded string.

The keygen is not 100% correct regarding from this point of view.

I.M.H.O. the correct way was, if the keygen generate random chars matching the required conditions before inserting the name you chose.

Once you get the algo decrypted which is very simple and i consider the second keygenme solved.

Do you want to change the algo to make harder challenges for this keygenme (maybe others have to learn something from it)?

Edited August 8, 2016 by GIV
Few spell changes.

[kao]

There's nothing wrong with Insid3Code's keygen and hardcoding few chars. It generates valid serials, that's all that matters. 

 

What would be the point of making more of the same? People who can get around Eazfuscator are bored by the crap algorithms. And people who can't get around Eazfuscator.. Well, they can use these 2 challenges to learn.

[GIV]

Yep.

OK.

More complicated algo for key verification would not be so easy (i think).

Also the X64 keygenmes protected with Eazfuscator could be interesting enough.

Anyway could someone put here the 2 files unpacked?

[kao]

x64 keygenme with Eazfuscator? Hmm, ok, let's try that..

 

[GIV]

OK.

Here is a X64 build.

 

Simple Keygenme 2016 - giv.rar

[Ahmad_k]

There is a problem in the executable, i cannot run it properly. It closes immediately after putting any character in username field.