{
 "id": "15cd8y",
 "title": "201212231409",
 "title_time": "2012-12-23T14:09",
 "author": "[deleted]",
 "account": "A858DE45F56D9BC9",
 "subreddit": "A858DE45F56D9BC9",
 "created_utc": "2012-12-23T22:09:05Z",
 "permalink": "https://www.reddit.com/r/A858DE45F56D9BC9/comments/15cd8y/201212231409/",
 "arctic_shift": "https://arctic-shift.photon-reddit.com/api/posts/ids?ids=15cd8y",
 "sources": [
  "community-archive",
  "arctic-shift"
 ],
 "body": "F8E2417DCC2CC99C 9E1804CF1A268158 ",
 "body_source": "community-archive",
 "body_other_version": "0000000000000000",
 "body_hex_chars": 32,
 "bytes": 16,
 "score": 23,
 "num_comments": 15,
 "category": {
  "code": "S",
  "label": "S solved special"
 },
 "kind": "manual",
 "encryption": "decrypted",
 "status": "solved",
 "summary": "'Merry Christmas'. 3DES-CBC, key MD5(name), IV presumed.",
 "content_type": [
  "Seasonal greetings and ASCII art"
 ],
 "cipher": {
  "algorithm": "3DES-EDE2 (two-key Triple DES)",
  "mode": "CBC",
  "padding": "PKCS7",
  "key_derivation": "MD5(password)",
  "password_recipe": "name",
  "password": "A858DE45F56D9BC9",
  "key_hex": "34a14a42e98ff96095af56604e290cae",
  "iv": {
   "status": "presumed",
   "value": "CF40AD098EC6A4A8",
   "first_block": "Merry Ch"
  },
  "steps": [
   [
    "Derive the key",
    "Password = <code>A858DE45F56D9BC9</code> (name); key = MD5(password) = <code>34a14a42e98ff96095af56604e290cae</code>, used as a two-key 3DES key."
   ],
   [
    "Decrypt",
    "3DES-EDE2 in <em>CBC</em> mode, then strip the PKCS7 padding."
   ],
   [
    "Presumed IV",
    "The IV was never published. Assuming the first 8 bytes are \"Merry Ch\", the IV is D(C0) XOR that block = <code>CF40AD098EC6A4A8</code>. A presumed value, not a recovered one: every block after the first decrypts the same way whatever the IV is."
   ]
  ],
  "raw": "Merry Christmas",
  "presumed_prefix": "Merry Ch"
 },
 "plaintext": "Merry Christmas",
 "word_layer": null,
 "credit": null,
 "decoded_layers": null,
 "guids": null,
 "count_from_length": null,
 "run": null,
 "known_solution": [
  {
   "Method": "3DES-CBC, key MD5(name)",
   "Result": "'Merry Christmas'",
   "Explanation": "Verifier check passes (2-key 3DES-CBC)",
   "Re-checked": "hex -> 2-key 3DES-CBC"
  }
 ],
 "tags": [
  "automated (decryptable)",
  "2012",
  "Solved special post",
  "manual",
  "edited",
  "key: name",
  "seasonal greetings and ascii art"
 ],
 "title_zone_hours": -8,
 "title_zone": "UTC−8",
 "writeup": {
  "title": "201212231409 — Merry Christmas",
  "markdown": "Status: **verified** against the archived post.\n\nThe body is whitespace-separated hexadecimal. Decode it to ciphertext, then decrypt with two-key 3DES (DES-EDE-CBC):\n\n- key: `34A14A42E98FF96095AF56604E290CAE`\n- IV: `CF40AD098EC6A4A8`\n- padding: PKCS#7\n\nThe plaintext is:\n\n```text\nMerry Christmas\n```"
 },
 "page": "posts/15cd8y/"
}