Question

Describe the meet-in-the-middle attack against Triple DES (EDE mode).

Answer 1

Triple DES use EDE(Encrypt,Decrypt,Encrypt) mode to encrypt the data in this suppose we are using three different key K1,k2,k3 in this scenerio first we encrypt the plain text or data with K1, then we decrypt the resultant encrypted data with key K2 then we finally encrypt the data from previous operation using K3 then we have our final encrypted data which provides you the 168- bit of DES means it requires the the 2¹⁶⁸ encryption logics which is very much difficult to anybody to do this huge no of operation to decrypt the the encrypted data.

but if you use same key (k1=k3) for encryption while applying tripple DES then it's provides you the 116-bit of DES means it requires the 2¹¹⁶ encryption logics which is very much difficult to anybody to do this huge no of operation to decrypt the the encrypted data if you does have the key.

For the Decryption of data the process is just reversed see if we are using three different key K1,k2,k3 in this scenerio first we decrypt the encrpted text or data with K3, then we encrypt the resultant decrypted data with key K2 then we finally decrypt the data from previous operation using K1 then we have our final data in plain text.

By this whole scenerio tripple DES is secure against Meet in the middle attack as we know that it can be able to reduce the bruteforce processes to a huge number but not that much as tripple DES provides us the minimum of 2¹¹⁶ encryption logics which is very difficult to process this much no of operation by any attacker.

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