can we change the present cipher s box output table

Present cipher s box table contains standard form of inputs correspondance to the outputs. Can we change the outputs with regarding some other inputs. eg: input0000 maps to output1100 and input1111 maps to output0010. shall we change the outputs eg:input0000 maps to output0010, input 1111 maps to output1100??

Answer 1

[Sameer]

Hi Mohanapriya

From my understanding, you want to modify the output mappings of an “S-box” in a cipher.

Yes, you can change the outputs of an “S-box”, but doing so will alter its cryptographic properties and potentially its effectiveness. An “S-box” is a fundamental component in block ciphers, and its design is critical for ensuring security properties.

Considerations When Modifying an S-box:

1. Avalanche Effect: A small change in the input should result in a significant change in the output. Ensure that the new mapping maintains this property.
2. Non-linearity: The “S-box” should be highly non-linear to resist linear attacks. Verify that the new mappings do not introduce linear patterns.
3. Bijectiveness: If the “S-box” is used in a context where it needs to be bijective, ensure that each input maps to a unique output and vice-versa.
4. Cryptographic Strength: Changing the mappings might weaken the cipher unless carefully analyzed. Use cryptanalysis techniques to evaluate the strength of the new “S-box”.

Hope this helps!