Context
We have to find the password of this person.
We have the memorandum.txt file.
This file is a Memo. A Memo is a short message or description that is attached to a transaction or interaction on a blockchain network.
When you perform a transaction on a blockchain network, such as sending cryptocurrency tokens from one address to another, you may have the option to include a memo. The memo is an optional field where you can include additional information about the transaction.
Resolution
The memo is in hexadecimal, we need to decode it.
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import binascii
with open('memorandum.txt', 'r') as f:
memo = f.read()
memo_bytes = binascii.unhexlify(memo)
print(memo_bytes)
At the end of the decoded text, there is:
We have this URL: https://shorturl.ac/mysecretpassword that is a Rick Roll.
We this other kind of endpoint:
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/ipfs/bafybeia5g2umnaq5x5bt5drt2jodpsvfiauv5mowjv6mu7q5tmqufmo47i/metadata.json
By searching the net, I learned that IPFS (InterPlanetary File System) is a peer-to-peer distributed file system designed to create a more decentralized and resilient web infrastructure. It is a protocol that enables the storage and retrieval of files on a global scale without relying on traditional centralized servers.
Thanks to this site, we know how to use it: https://decrypt.co/resources/how-to-use-ipfs-the-backbone-of-web3
I searched for it on ipfs.io:
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https://ipfs.io/ipfs/bafybeia5g2umnaq5x5bt5drt2jodpsvfiauv5mowjv6mu7q5tmqufmo47i/metadata.json
We end up on this JSON file:
Another file is mentionned (ipfs://bafybeic6ea7qi5ctdp6s6msddd7hwuic3boumwknrirlakftr2yrgnfiga/mystere.png).
We access the file the same way.
It looks like a token for an account. I found on the net that Sepolia is a blockchain.
I searched for the account we have on https://sepolia.etherscan.io/
In the “Contracts” tab, in the Constructor Arguments, there is the flag !!
