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Reverse engineering

By : Yacine Hebbal

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What is reverse engineering ?

Reverse engineering is the process of extracting the

knowledge or design blueprints from anything man-made.

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What is reverse engineering ?

Reverse engineering can be practiced on: mechanical

devices, electronic components, or software programs, and we

will focus on reversing software programs

Reversing applications can be seen as "going backwards

through the development cycle.”

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What is reverse engineering ?

compiling

decompiling

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Where do we need it?It is used for

1-Evaluating the level of security that the application

provides

2-Analyzing and eventually defeat various copy protection

schemes (cracking)

3-Locating vulnerabilities in operating systems and other

software

4-Reversing Cryptographic Algorithms

5-Infecting application by viruses or to healing them from

the infection

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Is it legal ?

It depends on why you are reversing software, it is legal for

education purposes and illegal for stealing password and

private information

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Terminology

Patching : A technique of modification of a program.

Serial fishing : Finding the correct password for an

application.

Keygenning : Finding the algorithm that generate the

password of an application.

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So how to do it ?

Software reverse engineering requires a combination of

skills & tools

So to do it we need:

- Tools

- Knowledge

- A working mind , curiosity & the desire to learn

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So how to do it ?

Tools

1-disassemblers: are programs that let us get the

assembly code from any application such as

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IDA PRO DISASSEMBLER

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OLLY

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So how to do it ?

Tools

2- Debuggers: they are programs that let us execute

assembly code and see the results of any instruction

IDA & Olly are also debuggers

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So how to do it ?

Tools

3-Hex editors: they show the content of any file

(programs) in hexadecimal format, they allow us

to modify instructions or to get some information

(header information for ex)

Ex: hex workshop

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HEX WORK SHOP

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So how to do it ?

Tools

4- Other tools : We need also some other tools like :

- Peid

- ImpRec

- metasploit

- …

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Let’s make hands dirty !!!!

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1- Patching applications

Bypassing Authentication

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2 - Password fishing

Static passwords

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3 - Password fishing

Dynamic passwords

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4 - Keygenning

Create keygen

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Some defense methodes

To protect your application there is many defense methods such as:

Packers

Protectors

Encryption algoritms

…

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Packers

they compress the application so the constant like text for

example will be changed, and they will be restored after the

execution of the application so we can’t see theme before the

execution

Ex : UPX , Morphine , Aspack , FSG …

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Protectors

they are small programs fused with the application that

can detect the debugger or the disassembler so they won’t let

us reverse the application

Sometimes we can find a packer and protector in the same

time

EX : YodaEncrypt , ARMprotect …

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Encryption

Also there are some other techniques like encrypting the

password by using hash functions like MD5, SHA-1 …

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Buffer overflow vulnerability

Overview ….

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Buffer overflow vulnerability

Exploitation

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Links:

http://www.kromcrack.com/

http://tuts4you.com/

http://www.newbiecontest.org

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Thank you

For you attention