201309150859 1mfi3a

explained decrypted filler

seed 521

Metadata

Post ID: 1mfi3a
Title: 201309150859 → 2013-09-15 08:59 on A858's clock
Posted (UTC): 2013-09-15 12:59:57
Timezone: UTC−4 · title 08:59 against posted 12:59 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(A858DE45F56D9BC9201309150859) = 8c391a861dedc4e65aa969e6211bfe7d (name+title)
GUIDs: 8
Filler GUID seed: new Random(521).Next(9) ✓ verified
Run: Run 53 (seed 26,950,390) (seed)
Draw: 68 · 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: 2 · 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 = A858DE45F56D9BC9201309150859 (name+title). Key = MD5(password) = 8c391a861dedc4e65aa969e6211bfe7d, 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 6712e064-2fee-8d99-adaa-e64467daa695
  2 8f83c776-cb70-6ea9-930e-2dda7052f9c9
  3 17fa11c0-ab00-8a6d-8403-46f612aea9e5
  4 5bb14133-2500-6cd1-83b1-19ea0ca638aa
  5 43035c65-6f3b-3e96-ae66-8c983008d92c
  6 eb4415f0-258b-79b6-b014-244f12a5b607
  7 1998f670-a9b7-34a7-bed2-b32dc20b27ad
  8 0276ff17-9722-7735-8f2c-1c0eabd737ea

Explanation

Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 86863737. Exactly this sequence comes out of new Random(521).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 68 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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