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

On 28/03/25 04:56, Marcel Logen wrote:

colin in sci.crypt:
 [...]
 

Looks like it's up to the implementation of how it implements padding
and how many bytes it requires to do it.
>
$ openssl enc -aes-256-cbc -in 511bytes.txt -pass pass:1234 -pbkdf2 | wc -c
528
$ cat 511bytes.txt | aespipe -e aes256 -P password.txt | wc -c
512
>
The way I understand it is AES is only a basic building block that takes
a 128bit block and scrambles it to a different 128bit block.
All the other building blocks ( eg: salt, IV, padding, mode of operation
etc ) are added in to suit what the implementation requires.

 | user15@o15:/tmp$ stat -c '%s' 511bytes.txt
| 511
 | user15@o15:/tmp$ openssl enc -aes-256-cbc -in 511bytes.txt -pass pass:1234 -pbkdf2 | wc -c
| 528
 | user15@o15:/tmp$ openssl enc -aes-256-cbc -in 511bytes.txt -pass pass:1234 -pbkdf2 -nosalt | wc -c
| 512
 -nosalt => 512
 

I think I have got my head around it now.
Openssl adds salt by default.
At least 1 byte of padding is always added ( up to 16 )
Hence with -nosalt
511 -> 512
512 -> 528 ( one block full of just padding )
513 -> 528
527 -> 528
528 -> 544