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Old 01-15-2019, 18:55
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Hexpand - hash key legth attack for Window

Hexpand - hash key legth attack for Window

Original source location:
This version is ported to Windows.

Version of OPENSSL used:
OpenSLL 1.1.0e 16 Feb 2017
The fallowing files should be present:
These filess are present in SSL_DLLS.rar rar archive!

I've used Visual Studio 2008 Command Prompt
for compling source code with nmake.exe
see Compile.bat

Hexpand is a tool for automating hash length extension attacks.

## What's a length extension attack? ##

Hash length extension attacks allow an attacker to construct the `H(secret|message|append)`
given only `H(secret|message)` and the length of `secret|message`.
The attack uses the output hash to reconstruct the internal state of the hash function.
From there, it is trivial to feed the hash function the data to be appended and output the new hash.

How this works?
We continue hasing for we "left" by setting hash internal state:
SHA512_CTX.h[] for SHA and MD5_CTX.a, MD5_CTX.b, MD5_CTX.c, MD5_CTX.d for MD5
The data to be append is standard padding of the hash algorithms!
Plus of course the message to be append!

Missing dlls (OpenSLL), should be placed on hexpand.exe location:
Attached Files
File Type: zip hexpandw.zip (49.1 KB, 12 views)
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