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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How is lite hash rate (LHR) of Nvidia implemented?

Nvidia limited some of their GPUs with LHR to decrease the performance of Ethereum mining. What in detail is LHR doing? It seems to limit non sequential memory operations (which is actually not what ...
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2 answers
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How to know which hashing algorithm is being used?

I’ve been reading about digital signatures getting ready for some certification, and there is one question regarding this topic, that I don’t really understand. Let’s say that I receive a plaintext ...
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Log input data and resulting hash for CC_MD5 calls in an iOS app with Frida

I am trying to understand the usage of calls to CC_MD5 in an iOS application. From Apple's man page I can see that when it is called it requires 3 arguments: extern unsigned char * CC_MD5(const void *...
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How to find how a hash in generated in an iOS app

I'm currently working on an iOS app to replicate a signature which looks to be generated with a MD5 hash. I'm currently using Frida, but haven't had any luck replicating it. I've used the script to ...
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Determining a password-hashing function knowing plaintext + output

I have a password that has been stored and I'd like to figure out how it's been 'transformed' to be stored in my database. The plaintext password is: k4oK203$ And the password as it is stored 'crypted'...
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104 views

Hashing algorithm of length 50

I have been trying to reverse-engineer an Android application using Jadx for static analysis and Frida for dynamic analysis. The end goal is to be able to re-create the request signature, sent as a "x-...
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1 answer
161 views

cracking SHA256 if you think you know its original value but don't know which is it

I have a hash and what I think is its original value DRMSoftwareRadio-MERLIN-00000218 20030130 Frank Garnier Frank.Garnier@rnw.nl Witte Kruislaan 55 Hilversum 1217AM Netherlands ...
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180 views

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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4 answers
2k views

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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1 vote
1 answer
171 views

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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1 answer
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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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3 votes
1 answer
175 views

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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1 vote
1 answer
231 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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1 vote
0 answers
128 views

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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1 answer
2k 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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0 answers
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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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1 vote
1 answer
245 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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1 vote
1 answer
2k 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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2 votes
2 answers
4k views

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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7 votes
1 answer
329 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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2 answers
192 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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1 vote
1 answer
533 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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2 votes
0 answers
210 views

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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3 votes
8 answers
3k views

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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1 vote
2 answers
1k 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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1 answer
329 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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-1 votes
1 answer
950 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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2 votes
1 answer
626 views

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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5 votes
3 answers
1k views

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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4 votes
0 answers
2k views

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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3 votes
2 answers
562 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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2 votes
2 answers
581 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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3 votes
2 answers
2k views

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 ...
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