known-plaintext attack
 

Hi,

its me again.

I do have a encrypted file and also do have the plaintext. How can I find out the encryption algo and how can i get the key?
They both have the same length. Thats all i know:)

Ciphertext hex is:

29 6E 0D 7D F1 37 48 C4 FC 80 46 C2 50 54 40 BB 4F AE A0 08 D3 BD 38 7D AF 56 2C E9 27 3E 50 6A 30 45 AC AC 13 7C 4A DC A7 0F A5 56 4E 5C C0 13 2D 07 C8 78 1F 4F 52 E8

Plaintext hex is:

52 75 6E 53 63 72 69 70 74 31 3D 4D 6F 64 65 73 4D 61 6E 61 67 65 72 2E 4C 6F 61 64 53 65 6C 65 63 74 65 64 4D 61 74 65 72 69 61 6C 73 28 22 44 65 66 61 75 6C 74 22 29


thanks for all the help here.

-e

With that information it's impossible to find algorithm or key. The algorithm is never kept secret, the security comes from the key.

All one-time-pads are a guaranteed solution for example and you can create an infinite number of custom encryption algorithms which all decrypt that exact ciphertext to that exact plaintext using whatever key you like.

I do have more files in ciphertext and plaintext. Would it be possible with more data?

-e

Reducing an infinite number by a finite number still results in an infinite number.

Ok. Thx.

How about checking the executable which is decrypting/encrypting the files.
I do have that but could not find the encryption scheme.

-e

Yes, that's the normal way to go. Unless something really strange is going on, this executable will contain the decryption algorithm and (depending on what the encrypted data is used for) might also contain the key or something equivalent.

ok. I will look more into that.
If I do not find anything, i will post here.

-e