201309201232 1msama

explained decrypted filler

seed 258

Metadata

Post ID: 1msama
Title: 201309201232 → 2013-09-20 12:32 on A858's clock
Posted (UTC): 2013-09-20 16:32:55
Timezone: UTC−4 · title 12:32 against posted 16:32 UTC
Author: [deleted]
Account: A858DE45F56D9BC9 main account
Subreddit: r/A858DE45F56D9BC9 the main subreddit
Category: F3 filler: 3DES(name/title) → GUID list, seed known
Size: 272 hex characters · 136 bytes
Cipher: 3DES-EDE2 (two-key Triple DES), ECB, PKCS7
Key: MD5(A858DE45F56D9BC9201309201232) = 57424b3bb5e9c0dffdd46819068fbcb3 (name+title)
GUIDs: 4
Filler GUID seed: new Random(258).Next(9) ✓ verified
Run: Run 53 (seed 26,950,390) (seed)
Draw: 117 · predicted N = 4 ✓
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: 1 · 0
Tags: automated (decryptable)2013Encrypted masked GUID listkey: name+titlerun: seed

From the post to its content

As posted (encrypted)

F8D933BD81F74D8B 12DDD2C2D75DE36F D2D992DEBF47B097 6787E0A9FFA1FF02 2EC007E7EE3401C4 AD89B3C93C27B7E8 519DD516A9F8B972 1E6E1A1E5A0BE566 FB0F03C260B0F479 003C8427368BA5ED FD2805409511E4B6 53DF630F360D5301 891643CD40333549 A0D011731D088138 A02387BD480CEDD0 918EBD06E26AA9DF 8618B771FFC27B3F

Read the ciphertext. Strip whitespace: 272 hex characters = 136 bytes = 17 8-byte 3DES blocks.
Derive the key. Password = A858DE45F56D9BC9201309201232 (name+title). Key = MD5(password) = 57424b3bb5e9c0dffdd46819068fbcb3, used as a two-key 3DES key.
Decrypt. 3DES-EDE2 in ECB mode, then strip the PKCS7 padding. The plaintext is 4 GUIDs as hex (shown below).

Decrypted: GUID list

  1 55d93f48-3f06-4445-81d2-930a3607cb4e
  2 bc510cc2-7916-4f88-869c-208d397cbde6
  3 5672535d-7533-07db-bee1-0ddd15eec641
  4 f4fc0b14-92c8-5ddf-872d-6ef424d434cf

Explanation

Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 4405. Exactly this sequence comes out of new Random(258).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 117 of Run 53 (seed 26,950,390): new Random(26950390), 4·Next(1,12) per post. The RNG predicts N = 4; the post has N = 4 ✓. 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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