201207271402 x9mi7

explained decrypted filler

3DES(name+name) ECB, 8 GUIDs, seed 766

Metadata

Post ID: x9mi7
Title: 201207271402 → 2012-07-27 14:02 on A858's clock
Posted (UTC): 2012-07-27 20:59:42
Timezone: UTC−7 · title 14:02 against posted 20:59 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)
New here: Missing from the community archive; decrypted here for the first time. (new results)
GUIDs: 8
Filler GUID seed: new Random(766).Next(9) ✓ verified
Run: Run 18 (seed 6,051,781) (seed)
Draw: 2 · predicted N = 8 ✓
Machine boot: 2012-07-27 19:15–19:16 (seed = uptime at app start)
Sources: arctic-shift · body from arctic-shift
Links: Reddit · Arctic Shift · JSON
Score · comments: 1 · 0
Tags: automated (decryptable)2012Encrypted masked GUID listarctic-onlykey: name+namerun: 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 = 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 5978db35-1d4c-8039-a3fe-6d07e86d5c3b
  2 c768961e-5abd-57a4-992e-77751865771d
  3 54adaf11-bb7f-1a75-a019-f5beec00b20a
  4 61001c06-9880-0721-951e-7c7e733af8bd
  5 ae15d913-a1c5-096a-80d7-5be6efc9e7d6
  6 18625c2c-9a9b-839f-b5f6-be9c9f6973d8
  7 71c097a3-a300-1806-bd1f-aecf8f25264f
  8 2246cc76-e570-63be-9971-256e9a62f7a9

Explanation

Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 85100816. Exactly this sequence comes out of new Random(766).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 2 of Run 18 (seed 6,051,781): new Random(6051781), 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 19:15–19:16).
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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