201309161059 1mi5tl

explained decrypted filler

seed 87

Metadata

Post ID: 1mi5tl
Title: 201309161059 → 2013-09-16 10:59 on A858's clock
Posted (UTC): 2013-09-16 14:59:55
Timezone: UTC−4 · title 10:59 against posted 14:59 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(A858DE45F56D9BC9201309161059) = 6dc9adc8a6d5c3b8eb104f5a9b986a23 (name+title)
GUIDs: 8
Filler GUID seed: new Random(87).Next(9) ✓ verified
Run: Run 53 (seed 26,950,390) (seed)
Draw: 94 · predicted N = 8 ✓
Machine boot: 2013-09-12 09:30–10:30 (seed = uptime at app start)
Sources: community-archive, arctic-shift · body from community-archive
Links: Reddit · Arctic Shift · JSON
Score · comments: 4 · 0
Tags: automated (decryptable)2013Encrypted masked GUID listkey: name+titlerun: 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 = A858DE45F56D9BC9201309161059 (name+title). Key = MD5(password) = 6dc9adc8a6d5c3b8eb104f5a9b986a23, 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 4db1a482-1f6f-1ddc-849b-6fa6a83aff4b
  2 3b133cce-c3a8-3f75-be8a-8c63b2c46df3
  3 39bd393a-5c65-5985-b183-bae6f42f5ddf
  4 6a5bd321-2243-1ff7-8acf-c42075b168a6
  5 cc9d66f2-0a33-4fc7-9523-fcca4315d9cc
  6 cf902cae-1d45-50c6-9ed4-dee22f119f72
  7 a6a4f3fa-71e3-730e-881c-919820588774
  8 f77db1bb-c613-0703-b9b9-65fe7b2e4422

Explanation

Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 13514570. Exactly this sequence comes out of new Random(87).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 94 of Run 53 (seed 26,950,390): new Random(26950390), 4·Next(1,12) 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 2013-09-12 09:30–10:30).
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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