Re: What are the chances of this encrytion being broken?

On 24/03/2025 23:18, Marcel Logen wrote:

Richard Heathfield in sci.crypt:
 

On 24/03/2025 21:33, hal@invalid.com wrote:

 [...]
 

There's no sign at all of which program
encrypted it. Be it AES or not,

>
It's not. How do I know? Well, take a look at the histogram:
>
Code  49 ( 1)     19 (  2.70%)
Code  88 ( X)     18 (  2.55%)
Code 100 ( d)     16 (  2.27%)
Code 105 ( i)     16 (  2.27%)
Code  69 ( E)     15 (  2.13%)
Code  70 ( F)     15 (  2.13%)
Code  82 ( R)     15 (  2.13%)
Code  99 ( c)     15 (  2.13%)
Code 108 ( l)     15 (  2.13%)
Code 111 ( o)     15 (  2.13%)
>
For a flat ciphertext we'd expect to see each byte value 2-3 times, but
in your ciphertext 3/4 of the byte values don't appear /at all/.

 ACK
 But what about Base64?

Excellent point! In fact, the character set is A-Za-z0-9/+ ... which does suggest very, very strongly that this is base64-encoded.

 The Base64 decoded 'text' has 528 bytes.
 There are 228 different byte values, most of which (88) occur once
and four seven times. I would expect 528/256 = 2.0625 per byte value.

Clearly a lot flatter.
Code  80 ( P)      7 (  1.33%)
Code 106 ( j)      7 (  1.33%)
Code 113 ( q)      7 (  1.33%)
Code 148 (!!)      7 (  1.33%)
Code  32 (  )      6 (  1.14%)
Code  61 ( =)      6 (  1.14%)
Code 213 (!!)      6 (  1.14%)
Code  22 (!!)      5 (  0.95%)
Code  37 ( %)      5 (  0.95%)
Code  40 ( ()      5 (  0.95%)
Still pretty spiky, though.
We can now conclude that this is not only not AES but also not AES shrouded by base64, but yes, a base64 does seem pretty likely. What's under it still looks home-grown, though.
Are you thinking what I'm thinking? i.e. time to see the algorithm?
--
Richard Heathfield
Email: rjh at cpax dot org dot uk
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