A858DE45F56D9BC9 archive

201309132059 1mco51

explained decrypted filler

seed 435

Metadata

Post ID
1mco51
Title
201309132059 → 2013-09-13 20:59 on A858's clock
Posted (UTC)
2013-09-14 00:59:59
Timezone
UTC−4 · title 20:59 against posted 00:59 UTC
Author
[deleted]
Account
A858DE45F56D9BC9 main account
Subreddit
r/A858DE45F56D9BC9 the main subreddit
Category
F3 filler: 3DES(name/title) → GUID list, seed known
Size
272 hex characters · 136 bytes
Cipher
3DES-EDE2 (two-key Triple DES), ECB, PKCS7
Key
MD5(A858DE45F56D9BC9201309132059) = c9aff58c3966068945b4a233249bccd1 (name+title)
GUIDs
4
Filler GUID seed
new Random(435).Next(9) ✓ verified
Run
Run 53 (seed 26,950,390) (seed)
Draw
32 · 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
2 · 0
Tags
automated (decryptable)2013Encrypted masked GUID listkey: name+titlerun: seed

From the post to its content

As posted (encrypted)

BF5D72710E6E5EC6 06EAAE69FC3DCA80 428A31A68D63501B 8562A07AD069C3BC 0AF80D849326503F 7BBB980879826997 6FA612F16E3514B9 1DE3913910919D62 82BF6CB37EF2101E E636094AEF3BDA69 30F27824D292C22C 536383D787AD660E 688A520D74EE17B4 7669C6E0EAAE332E 9A478EF44214BE4F 92D08607270F3E97 F177CCBC55A4C09D
  • Read the ciphertext. Strip whitespace: 272 hex characters = 136 bytes = 17 8-byte 3DES blocks.
  • Derive the key. Password = A858DE45F56D9BC9201309132059 (name+title). Key = MD5(password) = c9aff58c3966068945b4a233249bccd1, 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 a5ff66ff-8ef7-8d57-8d24-09fc438ad380
  2 3bf9c1ac-d72c-4a29-b6c9-28c965a78013
  3 fc028ec4-cefe-799c-8ffc-0ff796e56bef
  4 fdf1131b-7679-32d5-8797-5be12fc6c50f

Explanation

  1. Explain the mask digits. The version nibble (13th hex digit) of each GUID, read in order, gives 8473. Exactly this sequence comes out of new Random(435).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.
  2. Explain the count. This post is draw 32 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).
  3. Conclusion. Filler. The content is fully explained by the two RNGs.

Related

Findings: Mask digit · Count RNG & runs