201207091843 w9irj

explained decrypted filler

seed 19

Metadata

Post ID: w9irj
Title: 201207091843 → 2012-07-09 18:43 on A858's clock
Posted (UTC): 2012-07-09 09:41:57
Timezone: UTC+9 · title 18:43 against posted 09:41 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(A858DE45F56D9BC9A858DE45F56D9BC9) = 0dcc4bd9e114ebc42078977dc9125404 (name+name)
GUIDs: 10
Filler GUID seed: new Random(19).Next(9) ✓ verified
Run: Run 15 (seed 117,733,640) (seed)
Draw: 13 · predicted N = 10 ✓
Machine boot: 2012-07-06 08:59–12:59 (seed = uptime at app start)
Sources: community-archive, arctic-shift · body from community-archive
Links: Reddit · Arctic Shift · JSON
Score · comments: 4 · 6
Tags: automated (decryptable)2012Encrypted masked GUID listkey: name+namerun: 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 = 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 10 GUIDs as hex (shown below).

Decrypted: GUID list

  1 5c79be36-9fa2-5ae6-87a7-81742a3a393c
  2 dceb9cd3-2b8c-368d-8445-7e055abe4d98
  3 689fb000-5b60-0ae1-82e0-2d271e902019
  4 3c51f1c0-7929-5cd0-a249-98c63df541a9
  5 35e6c00d-c920-757e-94f8-1a85981f4ec7
  6 07fb877a-c68c-14db-ae6a-052de1fc40e0
  7 9223df22-c67e-3842-a83b-37c256998674
  8 42b84d72-2852-8e23-a24d-6c018b6ae748
  9 b80269f0-5123-2161-8f44-4af4d00a5b26
 10 283c1df8-0f6c-2f68-a145-6bc67abff49c

Explanation

Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 5305713822. Exactly this sequence comes out of new Random(19).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 13 of Run 15 (seed 117,733,640): new Random(117733640), 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 2012-07-06 08:59–12:59).
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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