201212040050 148ymy

explained decrypted filler

seed 305

Metadata

Post ID: 148ymy
Title: 201212040050 → 2012-12-04 00:50 on A858's clock
Posted (UTC): 2012-12-04 05:50:14
Timezone: UTC−5 · title 00:50 against posted 05:50 UTC
Author: [deleted]
Account: A858DE45F56D9BC9 main account
Subreddit: r/A858DE45F56D9BC9 the main subreddit
Category: F3 filler: 3DES(name/title) → GUID list, seed known
Size: 592 hex characters · 296 bytes
Cipher: 3DES-EDE2 (two-key Triple DES), ECB, PKCS7
Key: MD5(A858DE45F56D9BC9201212040050) = 6366465a29c2e59207ab3980abc232e7 (name+title)
GUIDs: 9
Filler GUID seed: new Random(305).Next(9) ✓ verified
Run: Run 39 (seed 1,106,402,812) (seed)
Draw: 19 · predicted N = 9 ✓
Machine boot: 2012-11-20 22:02–00:02 (seed = uptime at app start)
Sources: community-archive, arctic-shift · body from community-archive
Links: Reddit · Arctic Shift · JSON
Score · comments: 1 · 0
Tags: automated (decryptable)2012Encrypted masked GUID listkey: name+titlerun: seed

From the post to its content

As posted (encrypted)

74E8F4569A1427D3 F2582FD9A2BE1CE8 F1B740AA293D1DFB 81C0629F5DA73BA8 4B9A1BC249357DD8 836B85625EF1BD90 3D6C6F70AD62DAE3 ABB8C534580C7C58 B51EE191E9D9A09B 569E1CF01148D236 C200F00CF9FC7707 95059DA5EC974159 5931FA44D1FFA87F 17346EED39D23114 F0D9A99529277802 3FF4273EBD1D7E7F 49A10B5D1DFFAB71 A9A9845315EDCEBF 71657574A43CECF5 5AF5F6C8056AB21A 80DCF0DAECE8760B EA221D42586C56B3 1B2838B2B7DDE837 A338BE6071ED9A60 4F42F6B7F5F570AA D09D16F71C70172E B3429CC117B2EB99 61CCF1F69CE81710 9F6CB534EB7136A4 96F03B56006C9E37 4A9E5496B749F7BF 9D5E91EB689E511A 76BBFE40F33F25A3 55EAFAEC52EECEAB CB3BB72A8F4F2CEC 954B801A1E90F3F6 CC409ADCEBC6FA91

Read the ciphertext. Strip whitespace: 592 hex characters = 296 bytes = 37 8-byte 3DES blocks.
Derive the key. Password = A858DE45F56D9BC9201212040050 (name+title). Key = MD5(password) = 6366465a29c2e59207ab3980abc232e7, used as a two-key 3DES key.
Decrypt. 3DES-EDE2 in ECB mode, then strip the PKCS7 padding. The plaintext is 9 GUIDs as hex (shown below).

Decrypted: GUID list

  1 48cb7acf-4187-0d44-8561-49153bc92db5
  2 005e8bcc-6a2a-2c1e-8550-4d05302c5541
  3 d1337e67-6974-8662-ac2e-b17e200502be
  4 add40e18-5ae1-5fa8-a8f7-bef704555621
  5 f663ea42-ab22-82bb-96f6-9c4d523dcbb2
  6 8832a5f3-84b2-006b-af43-656666b2a204
  7 d7f22bef-72de-56ad-8b59-487e534f7be7
  8 f2fc65b6-8e8f-4a55-8308-be24b0d6d3c0
  9 f89cf09c-2012-69ff-8c8d-2bda1303ab2b

Explanation

Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 028580546. Exactly this sequence comes out of new Random(305).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 19 of Run 39 (seed 1,106,402,812): new Random(1106402812), Next(8,64) per post. The RNG predicts N = 9; the post has N = 9 ✓. The seed is the machine's uptime in ms when the app started (boot 2012-11-20 22:02–00:02).
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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