201308311859 1lgp2f

explained decrypted filler

seed 378

Metadata

Post ID: 1lgp2f
Title: 201308311859 → 2013-08-31 18:59 on A858's clock
Posted (UTC): 2013-08-31 15:00:00
Timezone: UTC+4 · title 18:59 against posted 15:00 UTC
Author: [deleted]
Account: A858DE45F56D9BC9 main account
Subreddit: r/A858DE45F56D9BC9 the main subreddit
Category: F3 filler: 3DES(name/title) → GUID list, seed known
Size: 528 hex characters · 264 bytes
Cipher: 3DES-EDE2 (two-key Triple DES), ECB, PKCS7
Key: MD5(A858DE45F56D9BC9201308311859) = bafb7ab2a27798c3f929e38b7c7a0b8d (name+title)
GUIDs: 8
Filler GUID seed: new Random(378).Next(9) ✓ verified
Run: Run 52 (seed 1,430,705,843) (seed)
Draw: 6 · predicted N = 8 ✓
Machine boot: 2013-08-14 07:34–10:34 (seed = uptime at app start)
Sources: community-archive, arctic-shift · body from community-archive
Links: Reddit · Arctic Shift · JSON
Score · comments: 0 · 0
Tags: automated (decryptable)2013Encrypted masked GUID listkey: name+titlerun: seed

From the post to its content

As posted (encrypted)

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

Read the ciphertext. Strip whitespace: 528 hex characters = 264 bytes = 33 8-byte 3DES blocks.
Derive the key. Password = A858DE45F56D9BC9201308311859 (name+title). Key = MD5(password) = bafb7ab2a27798c3f929e38b7c7a0b8d, used as a two-key 3DES key.
Decrypt. 3DES-EDE2 in ECB mode, then strip the PKCS7 padding. The plaintext is 8 GUIDs as hex (shown below).

Decrypted: GUID list

  1 082590ca-d1c2-1ad2-9163-9e5c7cb6ef3c
  2 2adf086a-8849-66d6-a55c-8e8fe735256b
  3 d864f114-a497-83bf-8cd0-de91eb83b3a1
  4 6a9c15c8-7f63-2384-bb6e-3fc5ce05c6fb
  5 2378a1d6-7dc1-74ad-9113-ad72685f066d
  6 54b75d9f-83d1-8d72-a3aa-079e7b164a71
  7 563753c4-4cda-242e-a72f-1ea63b0882da
  8 5fe0329c-3a43-082e-8be6-39b10d361a5b

Explanation

Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 16827820. Exactly this sequence comes out of new Random(378).Next(9): the per-post millisecond seed of the mask generator. The other 30 hex digits of each GUID are Guid.NewGuid() output and carry no message.
Explain the count. This post is draw 6 of Run 52 (seed 1,430,705,843): new Random(1430705843), 4·Next(1,12) per post. The RNG predicts N = 8; the post has N = 8 ✓. The seed is the machine's uptime in ms when the app started (boot 2013-08-14 07:34–10:34).
Conclusion. Filler. The content is fully explained by the two RNGs.

Metadata

From the post to its content

As posted (encrypted)

Decrypted: GUID list

Explanation

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