Hash3rror: CyberTalents Writeup

Cracking a Corrupted SHA-1 Hash

Category: Cryptography Level: Easy Points: 50

Hash3rror Cybertalents Challenge

Description

we got this corrupted hash password from a Pcap file with a note (password = sha-1(hash-result)).

HASH:77be5d24ed2e3e590045e1d6o7e84i50d2799c19f48ede46804a8734e287df120f

Solution

In this challenge, You’re given a corrupted hash from a .pcap file and a hint:

*password = sha-1(hash-result)*

The challenge hash is:

77be5d24ed2e3e590045e1d6o7e84i50d2799c19f48ede46804a8734e287df120f

Notice something strange? The hash contains non-hex characters: o and i.

1. Analyze the Hash Format SHA-1 hashes are 40 hex characters long and only use digits 0–9 and letters a-f.
2. Identify Corruption Look for invalid characters in the hash:

• o is likely 0
• i is likely 1
• Remove the invalid characters to find the correct hash

Corrected hash: 77be5d24ed2e3e590045e1d67e8450d2799c19f48ede46804a8734e287df120f

3. Reverse the Hash

Use an online hash cracker (like CrackStation, Hashes.com, or a custom Python script) to find what input generates this corrected hash.

Now, you can decrypt the correct hash using this tool to generate the password

As you can see the password is :

77be5d24ed2e3e590045e1d67e8450d2799c19f48ede46804a8734e287df120f:

s3cr3tpassword

4. Find the Flag

Now that we’ve successfully recovered the original hash-result (the preimage of the corrupted SHA-1 hash), it’s time to apply the final step based on the note provided:

password = sha-1(hash-result)

To do this:

1. Take the recovered password you got after correcting and cracking the corrupted hash.
2. Hash it again using the SHA-1 algorithm.
3. The result of this SHA-1 operation is the flag
4. You can use this tool or any reliable SHA-1 hashing tool (such as CyberChef, Hash Generator, or a local Python script) to perform this final encryption

If your cracked password is letmein, then:

SHA-1("letmein") = 0d107d09f5bbe40cade3de5c71e9e9b7

Flag: 83874343435092cb681c0d558a84bfeb389c32ed