# For the theoretic scenario of a brute force attack, how would you know if you succeeded?

That is something I never understood:

If you managed to brute force an AES encrypted text, how would you know you cracked it? After every attempt, you wold have to compare the text to an English dictionary right? That would take ages.

In the scenario of an AES encrypted program, you would get hexadecimal code every time even if you succeeded right? So you would not even know if you cracked it.

So i want to know, how do the best AES cracking methods of today work?

• This is probably a dupe from the question here but I'm not sure I like the way that question was asked. Maybe we can make this one block cipher specific? – Maarten Bodewes Dec 11 '16 at 23:43

If you managed to brute force an AES encrypted text , how would you know you cracked it ? After every attemt , you wold have to compare the text to an english dictionary right ? That would take ages .

Yes, thats why you could first check if most values are mapped to normal ASCII letters. If they do, then you could try that for more blocks, and when you got enough confidence you can check if those are most likely proper words, for example with dictionary. Since only marginal number of keys would result in such data, it wouldn't matter.

In the scenario of an AES encrypted program , you would get hexadecimal code every time even if you succeeded right ?

Every program in virtually any OS has a structure to it. You would find static elements, which would make checking plaintext even simpler: try to read file header, to see if this is valid header. Even if your specific code had no header, you could still easily predict that this code starts with 0x55 0x89 0xE5 (push ebp;mov ebp,esp), as thats typical procedure entry code (of course this is specific to architecture, example is given for x86).

Very same continues for virtually every data you can invent except for plain random data which is never reused anywhere.

So i wanna know , how do the best AES cracking methods of today work .

There are no AES cracking methods that we know of. There are some theoretic attacks on AES which are nowhere near being applicable. Problem in cracking any modern cipher is cost of trying all keys, check if decryption is right can be easily checked on most data.