201211081855 12uody

explained decrypted filler

seed 248

Metadata

Post ID: 12uody
Title: 201211081855 → 2012-11-08 18:55 on A858's clock
Posted (UTC): 2012-11-08 10:55:24
Timezone: UTC+8 · title 18:55 against posted 10:55 UTC
Author: [deleted]
Account: A858DE45F56D9BC9 main account
Subreddit: r/A858DE45F56D9BC9 the main subreddit
Category: F3 filler: 3DES(name/title) → GUID list, seed known
Size: 656 hex characters · 328 bytes
Cipher: 3DES-EDE2 (two-key Triple DES), ECB, PKCS7
Key: MD5(A858DE45F56D9BC9201211081855) = a53d6ad00ffe6d0d977ea95aca287ad8 (name+title)
GUIDs: 10
Filler GUID seed: new Random(248).Next(9) ✓ verified
Run: Run 38 (seed 1,045,884,937) (seed)
Draw: 111 · predicted N = 10 ✓
Machine boot: 2012-10-11 03:41–03:51 (seed = uptime at app start)
Sources: community-archive, arctic-shift · body from community-archive
Links: Reddit · Arctic Shift · JSON
Score · comments: 9 · 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: 656 hex characters = 328 bytes = 41 8-byte 3DES blocks.
Derive the key. Password = A858DE45F56D9BC9201211081855 (name+title). Key = MD5(password) = a53d6ad00ffe6d0d977ea95aca287ad8, used as a two-key 3DES key.
Decrypt. 3DES-EDE2 in ECB mode, then strip the PKCS7 padding. The plaintext is 10 GUIDs as hex (shown below).

Decrypted: GUID list

  1 1d502738-df6d-26cd-9d65-3b289ba1d02b
  2 bab06d5f-277c-537f-b224-f03315d91cbf
  3 31430b40-2eee-1067-a5e0-ea56d8b7f26c
  4 005728a3-e469-4d08-b8a8-3b54c9fddf77
  5 84861129-6a91-1fe4-8f43-061b93489eb8
  6 0a1351d1-2cff-27c7-99ec-e00c15934702
  7 c1257b0a-e2ec-0d9c-a2a8-5a0482e6de51
  8 acd248ea-84ce-7347-ab5b-ef09064423b2
  9 465f6642-4ae7-56d1-baa4-dd2b91315ce2
 10 8c6fd84e-dd5a-698b-bfa6-1bcd18843fbf

Explanation

Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 2514120756. Exactly this sequence comes out of new Random(248).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 111 of Run 38 (seed 1,045,884,937): new Random(1045884937), Next(8,64) per post. The RNG predicts N = 10; the post has N = 10 ✓. The seed is the machine's uptime in ms when the app started (boot 2012-10-11 03:41–03:51).
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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