201209040930 zb528

explained decrypted filler

seed 353

Metadata

Post ID: zb528
Title: 201209040930 → 2012-09-04 09:30 on A858's clock
Posted (UTC): 2012-09-04 00:30:05
Timezone: UTC+9 · title 09:30 against posted 00:30 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(A858DE45F56D9BC9201209040930) = d09ea6bbe0926c5334bf210d97fe3530 (name+title)
GUIDs: 10
Filler GUID seed: new Random(353).Next(9) ✓ verified
Run: Run 27 (seed 1,337,299,625) (seed)
Draw: 39 · predicted N = 10 ✓
Machine boot: 2012-08-15 10:07–10:24 (seed = uptime at app start)
Sources: community-archive, arctic-shift · body from community-archive
Links: Reddit · Arctic Shift · JSON
Score · comments: 3 · 5
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 = A858DE45F56D9BC9201209040930 (name+title). Key = MD5(password) = d09ea6bbe0926c5334bf210d97fe3530, 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 e4dc5a67-fbc3-1119-836e-d71241578d1d
  2 c8f43ef7-c1aa-36ee-90cb-d691567f59a8
  3 bc18bca5-76b2-4707-b7e9-bbce053c8fc7
  4 00eaa3a0-c800-8e3a-b4b6-2bd54ccbf660
  5 057abac9-db82-58c9-96f9-3ec818889931
  6 48ec4bfc-186d-0e34-ba4e-6e232d0b6fc2
  7 ab2d902b-0ce3-0fe2-99b1-8f13bfcb50ef
  8 33c53998-964b-4345-b86e-1e32008181e3
  9 1c6749e7-4423-5f65-8b0b-43222be6e591
 10 2b86643b-fd4e-340d-ac30-c7b020061ebd

Explanation

Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 1348500453. Exactly this sequence comes out of new Random(353).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 39 of Run 27 (seed 1,337,299,625): new Random(1337299625), 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 2012-08-15 10:07–10:24).
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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