201210101900 118u6t

explained decrypted filler

seed 206

Metadata

Post ID: 118u6t
Title: 201210101900 → 2012-10-10 19:00 on A858's clock
Posted (UTC): 2012-10-10 10:00:28
Timezone: UTC+9 · title 19:00 against posted 10:00 UTC
Author: [deleted]
Account: A858DE45F56D9BC9 main account
Subreddit: r/A858DE45F56D9BC9 the main subreddit
Category: F3 filler: 3DES(name/title) → GUID list, seed known
Size: 848 hex characters · 424 bytes
Cipher: 3DES-EDE2 (two-key Triple DES), ECB, PKCS7
Key: MD5(A858DE45F56D9BC9201210101900) = 84a78a4e30f9a536d70315dd63f23a54 (name+title)
GUIDs: 13
Filler GUID seed: new Random(206).Next(9) ✓ verified
Run: Run 35 (seed 854,622,578) (seed)
Draw: 524 · predicted N = 13 ✓
Machine boot: 2012-09-22 10:16–10:36 (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)2012Encrypted masked GUID listkey: name+titlerun: seed

From the post to its content

As posted (encrypted)

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

Read the ciphertext. Strip whitespace: 848 hex characters = 424 bytes = 53 8-byte 3DES blocks.
Derive the key. Password = A858DE45F56D9BC9201210101900 (name+title). Key = MD5(password) = 84a78a4e30f9a536d70315dd63f23a54, used as a two-key 3DES key.
Decrypt. 3DES-EDE2 in ECB mode, then strip the PKCS7 padding. The plaintext is 13 GUIDs as hex (shown below).

Decrypted: GUID list

  1 e6675272-d74b-3083-82a5-127b80318d3e
  2 df935008-9157-2f33-9ec0-ef4aecb4802f
  3 9ddf40f9-2f6d-6769-9c37-8fdf23caedb3
  4 e09b4032-0af3-485b-9689-2f892a61bb83
  5 792279c9-9570-1be6-816b-d12c0bc5fe6d
  6 21fee9d9-424f-5a60-923e-828f273e7b67
  7 ab487237-ec1f-18e3-92e4-a70532e26bdb
  8 651d7d57-4435-7fa0-a919-5f6ac52b6ee7
  9 01c17125-3462-4616-b62e-4972d7c4e5cb
 10 5921fd6c-b247-2d6a-aac3-acb22d22549e
 11 b5a86853-7a42-0ebe-b5d3-364840d9b503
 12 2f9272d6-c2b4-282e-9d77-4f979492b4b0
 13 7a22f659-54f9-23ef-af86-2a92c534c2cd

Explanation

Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 3264151742022. Exactly this sequence comes out of new Random(206).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 524 of Run 35 (seed 854,622,578): new Random(854622578), Next(8,64) per post. The RNG predicts N = 13; the post has N = 13 ✓. The seed is the machine's uptime in ms when the app started (boot 2012-09-22 10:16–10:36).
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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