I want to get 3DES to get a predictable result; assume I have:

key: [any]

data: [any]

then I want to apply 3DES decryption on key and data to get a specific result, such as:

decrypted 3DES: 12121212121212121212121212121212

Is this possible in theory?

  • 4
    $\begingroup$ Pick any key and let the data be the encryption of the target string (also note that 3DES by itself only encrypts 64-bit blocks). $\endgroup$ – SEJPM Jul 10 '19 at 6:47
  • $\begingroup$ Thanks! works perfectly $\endgroup$ – bcop Jul 10 '19 at 7:05
  • 2
    $\begingroup$ Changed the question, it seems you wanted a specific result, not a predictable result. You could of course say that you can predict specific details for a specific results, e.g. consisting of just ones and zeros. However, the only viable technique for that is to first pick a result and then encrypt that... $\endgroup$ – Maarten Bodewes Jul 10 '19 at 8:01

I want to apply 3DES decryption on key and data to get a specific result. Is this possible in theory?

Sure. 3DES is a functionally correct encryption scheme for any fixed key, so for any message there exists a(t least one) corresponding ciphertext value.

So if you want to have a specific decryption result $m$ using a specific key $k$, you simply choose the ciphertext $c$ as $c=E_k(m)$ and by correctness $D_k(c)=D_k(E_k(m))=m$.

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