201208011216 xhm7s

explained decrypted filler

seed 119

Metadata

Post ID: xhm7s
Title: 201208011216 → 2012-08-01 12:16 on A858's clock
Posted (UTC): 2012-08-01 04:13:37
Timezone: UTC+8 · title 12:16 against posted 04:13 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(A858DE45F56D9BC9A858DE45F56D9BC9) = 0dcc4bd9e114ebc42078977dc9125404 (name+name)
GUIDs: 8
Filler GUID seed: new Random(119).Next(9) ✓ verified
Run: Probable run 2 (seed 377,361,921) (probable)
Draw: 1 · predicted N = 8 ✓
Machine boot: 2012-07-27 19:10–19:12 (seed = uptime at app start)
Sources: community-archive, arctic-shift · body from community-archive
Links: Reddit · Arctic Shift · JSON
Score · comments: 9 · 3
Tags: automated (decryptable)2012Encrypted masked GUID listkey: name+namerun: probable

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 = A858DE45F56D9BC9A858DE45F56D9BC9 (name+name). Key = MD5(password) = 0dcc4bd9e114ebc42078977dc9125404, 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 6f31ecb9-14c1-8478-a3c5-d619cf2bc451
  2 c458475e-2e34-620d-abb5-cf37ce84483a
  3 b3b09dbc-ce8b-8cb6-a37f-37780dee0a06
  4 af503177-a2ac-8eed-8fb9-646dbe1b7974
  5 34d2b872-3e73-809e-bf21-ca0d3421c528
  6 64ae9613-06bd-42f6-8401-a0f83deb11ba
  7 b084007b-ece0-26b3-9157-d90191a0549a
  8 347bb8f3-8e5a-14dd-835c-2ab881b2cca3

Explanation

Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 86888421. Exactly this sequence comes out of new Random(119).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 1 of Probable run 2 (seed 377,361,921): new Random(377361921), Next(8,64) 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 2012-07-27 19:10–19:12).
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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