201509011522 3j99nf

solved decrypted manual

'The treasure is amoung the trash.' 3DES-CBC, key MD5(name), first block lost.

Metadata

Post ID: 3j99nf
Title: 201509011522 → 2015-09-01 15:22 on A858's clock
Posted (UTC): 2015-09-01 19:22:00
Timezone: UTC−4 · title 15:22 against posted 19:22 UTC
Author: [deleted]
Account: A858DE45F56D9BC9 main account
Subreddit: r/A858DE45F56D9BC9 the main subreddit
Category: S solved 3DES → text
Content: Operational notes
Size: 144 hex characters · 72 bytes
Cipher: 3DES-EDE2 (two-key Triple DES), CBC, PKCS7
Key: MD5(A858DE45F56D9BC9) = 34a14a42e98ff96095af56604e290cae (name)
IV: 793CB9632695D67F presumed: the IV was never published, so it is derived from a guessed first block (see the steps below)
Sources: community-archive, arctic-shift · body from community-archive
Links: Reddit · Arctic Shift · JSON
Score · comments: 10 · 56
Tags: post-cutover2015Solved special postmanualeditedkey: nameoperational notes

From the post to its content

As posted (encrypted)

c8ca968583244e3d 52b0218d0905cd2a 91ad308faca568e2 9ed4da07730c16d7 52d00de5130de58a bd605b631fd51c6a bcedef9fe505190b a941d0fa18b1c81e 55c6dd1d54a38bb0

Other archived version (the post was edited)

[deleted]

Derive the key. Password = A858DE45F56D9BC9 (name); key = MD5(password) = 34a14a42e98ff96095af56604e290cae, used as a two-key 3DES key.
Decrypt. 3DES-EDE2 in CBC mode, then strip the PKCS7 padding.
Presumed IV. The IV was never published. Assuming the first 8 bytes are the hex of "The " (the text below is hex-encoded), the IV is D(C0) XOR that block = 793CB9632695D67F. A presumed value, not a recovered one: every block after the first decrypts the same way whatever the IV is.

Decrypted

54686520747265617375726520697320616D6F756E67207468652074726173682E

Decode. The text is hex-encoded: each pair of characters is one byte, and decoding it gives the text shown below.

Decoded from hex

The treasure is amoung the trash.

Explanation

Solution summary

Method: 3DES-CBC, key MD5(name), IV not recovered; plaintext is hex-ASCII
Result: 'The treasure is amoung the trash.'
Explanation: First block lost; wiki documents the same key, mode and text; verifier checks the decoded blocks 1..
Re-checked: 3DES-CBC MD5(name), IV lost: hex-ASCII text, post `3j99nf`