Re: Which encryption algorithm used?

[exon <exon () home se>]

stevenr () mastek com wrote:
> Hi all
>
> Is it possible to identify the encryption algorithm used by looking at 
> the format of the encrypted string? Of course I understand we not may be
> 100% accurate but there could be a chance we hit home.

With a crypto worth anything what so ever; Absolutely zero.

You may be able to 'see' difference between different modes, but the 
output of a dual key-based encryption algorithm is supposed to be 
totally random (computer-generated whatever never is, that's why it "is 
supposed to be" instead of just "is").

> To give an example,
> probably a 32 character string could be a MD5 hash, and a string ending with
> == could be base 64 encoding.

MD5 hashes are one-way encryption, so I don't see what good it would do 
(you'd know when it's MD5 anyway, based on implementation guessing). I 
can think of a couple of other things which would be 32 chars long as 
well (including rot13 and xor :-) ).

Any encryption method might create output ending in ==, so this isn't 
really a good method.

> Is there any tool which can give a list of possible
> algos used, if provided with the encrypted string? anyone know of any site which
> has info on this ?

There aren't actually that many (good enough) algorithms, so a wild 
guess based on origin would probably be your best shot.

A couple of thumb rules here;
* Script-kiddies at home tend to protect their online gaming cheat-codes 
with 2048-bit DSA encryption.

* MS customers tend to use weaker cryptos and sillier hashing methods 
than the equivalent opensource solution, unless it's something really, 
really important and expensive.

* Protocols that transfer high amounts of data usually use 
CPU-friendlier cryptos (often weaker), than those written to control or 
authenticate one thing or another (like ssh).

> Thanks in advance
> Steve
>
> MASTEK
> "Making a valuable difference"
> Mastek in NASSCOM's 'India Top 20' Software Service Exporters List.
> In the US, we're called MAJESCO

/ae