Questions tagged [hash-functions]

An surjective function that maps a set of keys to a smaller data sets of a fixed length. Cryptographic hash-function are supposed to be practically impossible to reverse except by brute-force.

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Reverse Engineering a Vehicle Identification Number (VIN) encoding

Not sure if this is the right place so please point me to the right place if needed. I have an input of a VIN (Vehicle Identification Number) number with 17 characters, each character is either an ...
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4answers
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Is it possible to build an equivalent function just looking at the input and output of the original function?

Imagine you are reverse engineering a software. This software uses a library, which is obfuscated and encrypted. The library contains a function, lets call it secret_function. This function is a pure ...
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Does anyone recognise following (USB,HID?) encoding method?

Im reverse engineering a Keyborard RGB LED Control Software and there is a Library called "HidServ.dll" that seems to be the interface between the Keyboard and the Software. Every Function of that ...
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Tool to search known hash/encryption algo in files in Windows

I am looking for a tool (the best would be an Ida plugin) that can search files in a folder for a known hash (md5/sha1 etc.) and encryption (aes /rsa etc.). I know an Ida plugin called FindCrypt2 but ...
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145 views

How to detect md5 and sha256?

I use FindCrypt2 Ida plugin but it detect md4 and not md5 , and not detect sha256. How can I detect md5 in assembly? How can I detect sha256 in assembly? thanks
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Identification of RF hash algorithm

I have an unbranded LED lamp with a remote control. I would like to reverse the protocol of the remote but unfortunately I can't create my own packages. The frequency of the remote transceiver is 2....
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1answer
122 views

Reverse engineering Nextbike API and random 16 character pre-shared key

I am trying to get to know how Nextbike's API works. It's not a public API but capturing the outgoing traffic with my phone I can see all the traffic and endpoints that are being contacted. I've ...
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Techniques for reversing (basic) hash function

Hi I'm relatively new to RE, and I'm using GDB and Radare2. As part of a crackme I'm trying to reverse a weak hash function that's a little too complicated for me to undo by hand. I've been trying to ...
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700 views

CRC32 reverse engineer without knowing parameters, but knowing the input value

Dear members, I am trying to figure out the parameters of some hexadecimal CRC32 values I have. The values are: Value - input (before hashing) 55D3028A - J 73AF2D02 - O 6742BE71 - T I hope I can ...
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328 views

Struggling with an archive file format using “encryption”

I am currently working on a file format used to pack (storage only, no compression) different file types together for transport. There is some sort of very simple "encryption" used and so far I have ...
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223 views

Trying to reverse function to generate certain color strings from an HMAC signature - decompiled code LOOKS right, but my results differ

This might be a bit difficult to follow without context, but the gist of it is the following; I'm trying to reverse a certain application, and part of what I"m attempting to reverse in the app ...
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681 views

Understanding hashing in cookies

I am using a website whose cookies are as following (when I'm as a guest at 3 different instances in increasing order of time) : eyJ0YWxrX3N0YXRlIjowfQ\075\075|1497742098|...
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How to get file back from generated sha256 checksum?

The title seems little crazy, but I think that it is possible. Just think about it. If you create text file like this: Hello world! You get this checksum: ...
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233 views

Is there a way to find out which hash standard by studying the source code?

We have an embedded product, which we are carrying for several hardware iterations since more than 5 years ago. We have all the source code, most of it nicely documented. As the product is actively ...
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2answers
162 views

Identifying a very weak hash algorithm

I'm reverse-engineering a string translation file format for a particular game. It's ultimately just an ID-to-string map, where the IDs are four-byte integers. There are 1935 IDs in total; you can see ...
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292 views

Reverse-engineer digest http authentication

I have an iOS app which uses digest HTTP authentication with nonce which expires every 5 minutes. The client calculates response as following: HA1=MD5(username:realm:password) HA2=MD5(method:...
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What checksum is Super Smash Bros. Wii U using?

When you save a screenshot in Super Smash Bros. for Wii U on the SD card it writes to, it makes two files: a .JPG and a .BIN file. Both these files are in the format of HNI_XXXX.EXTENTION, where XXXX ...
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Reverse engineering a hash generated from IP and unixtime - How to approach?

There is a website that gives you a token and the unixtime to access a resource on another domain. I can use those 2 values to access it like that: Example: example.com/test.txt?st=[HASH]&e=[...
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8answers
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Is MD5 hashing of files a valid method of creating an anti-virus program?

Is it a good way to create Virus signature in MD5 or it is better in SHA1 or SHA256 and why it is?
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774 views

Extract decrypted token from EXE

EDIT As some people have pointed out, this exe file classifies as a 'virus' on some analysers. I can assure you this exe is from a very trusted source, and is actually part of a large puzzle (which ...
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197 views

Reverse-engineering the generation of a hash?

Using a forward proxy, I have logged two payloads that are POST requests to a site, and I was curious as to what the best way to determine how a particular attribute in the payloads was generated. ...
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670 views

Reversing sha1 hash with 2 captured hashes

As an exercise we need to reverse a SHA-1 to get the 'original' message. All we know is that the lowercase SHA-1 of the code gives: B39ECFBC2C64ADBB7C7A9292EEE31794D28FE224 And, the SHA-1 of the ...
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How do I find a collision for a simple hash algorithm

I have the following hash algorithm: unsigned long specialNum=0x4E67C6A7; unsigned int ch; char inputVal[]=" AAPB2GXG"; for(int i=0;i<strlen(inputVal);i++) ...
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3answers
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Hash algorithm written in C decompiled with IDA

I have been working on rewriting a program, although it uses a hash to fingerprint the file, I have used IDA to find the function doing the hash and what it is doing to the file before it sends it to ...
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Reverse Engineering a 8 bit CRC checksum

I am trying to create a communication interface using C Language to an Air conditioning system, after analyzing the data packets I have identified that the data packet is consist of an 8 bit CRC (I am ...
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444 views

Highscores being sent as hash

There is a game that has been created with Unity which I'm trying to beat. It sends your high-score to a site and gets posted there. I've sniffed the outgoing traffic and the game sends your username,...
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407 views

SHA + Mersenne Twister

I'm trying to decrypt some audio files. At first I thought that they were encrypted using Blowfish, but apparently "SHA + Mersenne Twister used for generate key and decrypt". What exactly does this ...
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Determine Hash Method - Busybox Linux

I'm trying to figure out how an ARM-Based device running Busybox Linux is storing hashes for users in a configuration file. Basically, the system allows you to backup the entire configuration to a ...