CrossCTF_2018: Kryptonight 2

Category: Crypto Points: 831 Description:

Have I got a little story for you What you thought was your daddy Was nothin' but a nc ctf.pwn.sg 1503 Creator - amon (@nn_amon)

Write-up

Like the previous one, when we connect to the socket, we get a pretty long paragraph (truncated for brevity),

$ nc ctf.pwn.sg 1502
0100fb8e8ac805899323371bb790db19218afd8db8e3755d8b90f39b3d5506a9abce4fa912244500000000ee8146d49fa93ee724deb57d12cbc6c6f3b924d946127c7a97418f9348828f0f02 -> 87c4e570653eb4c2b42b7a0d546559452dfab573b82ec52f152b7ff98e79446f
a058ac7d57151e908408783c383ee0e03b8ae39fdb5c30bbcc9386f0d53a77171f56304fc341420312a89172669135d0aff7d1e908148f7b98abb661583c26f3ffcbfbb64162ccc10f316b11a128679f[...]?

This one seems like Cryptonight but really isn't. Rather, it's Cryptonight Lite. Like before, making use of @nn_amon's library, we can solve this.

# node
> var multiHashing = require('multi-hashing');
undefined
> var data = new Buffer("7092df9d95b8c26ad2ca604a883176057b6c083a1a7ce4b253e328705b0a8e2040fc47bfbd6421bd9b3bf4839d3991b285e8795d260a4a3a5f99de319e98b69ad1c768e7c12e6ba0d4c44ac2dd9fec77b8ab63c1d84e49[...]", "hex");
undefined
> multiHashing['cryptonight-lite'](data, 1).toString("hex");
'23a97f80c04e39c500a5eb7fe2c969fa3ee30a4d2384e673e850494c4d0848f4'

Entering that into our other terminal, we then get our flag!

$ nc ctf.pwn.sg 1502
0100fb8e8ac805899323371bb790db19218afd8db8e3755d8b90f39b3d5506a9abce4fa912244500000000ee8146d49fa93ee724deb57d12cbc6c6f3b924d946127c7a97418f9348828f0f02 -> 87c4e570653eb4c2b42b7a0d546559452dfab573b82ec52f152b7ff98e79446f
a058ac7d57151e908408783c383ee0e03b8ae39fdb5c30bbcc9386f0d53a77171f56304fc341420312a89172669135d0aff7d1e908148f7b98abb661583c26f3ffcbfbb64162ccc10f316b11a128679f[...]?
23a97f80c04e39c500a5eb7fe2c969fa3ee30a4d2384e673e850494c4d0848f4
Flag: CrossCTF{d3ny_y0ur_m4ker_w3ll_b3_w4st1ng}

Therefore, the flag is CCrossCTF{d3ny_y0ur_m4ker_w3ll_b3_w4st1ng}.

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