# Using 3DES decryption to get a specific result

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?

• 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). – SEJPM Jul 10 '19 at 6:47
• Thanks! works perfectly – bcop Jul 10 '19 at 7:05
• 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... – Maarten Bodewes Jul 10 '19 at 8:01

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 $$D_k(c)=D_k(E_k(m))=m$$.