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In DES encryption, the IP table is shown. If the input given in hexadecimal is "0020 0940 0000 F008", which are the bit positions of "1" after the IP stage ? enter image description here

Bassel 1000
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    Welcome to Cryptography.se. Do you know how to use this table? – kelalaka Dec 28 '23 at 12:11
  • well, I have studied it theoretical but never used it in a question like that. I am student still btw. – Bassel 1000 Dec 28 '23 at 12:30
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    Hints: in the original document, this table is followed by: "That is the permuted input has bit 58 of the input as its first bit, bit 50 as its second bit, and so on with bit 7 as its last bit". Also, bits are numbered starting from 1 in reading order per big-endian binary representation. I think the question really is: what is the bit numbers of bits that are "1" in the output of IP for the stated input of IP. – fgrieu Dec 28 '23 at 13:27
  • @Bassel1000 if you wish you can answer your question. – kelalaka Dec 28 '23 at 21:22
  • if I can answer my question, why would I be asking? – Bassel 1000 Dec 29 '23 at 11:49
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    @Bassel1000 you are given hint to learn so if you learned you can answer, this is common and we encourage people about this. – kelalaka Dec 29 '23 at 17:27
  • See the answer to External data loading in DES showing data flow to and from a byte wide interface in a hardware implementation. Note the use of big-endian bit ordering in the byte wide interface where the MSB is bit position 1 and the LSB is 8. The inputs bytes are ordered 1 - 8, and the difference between the Initial Permutation and Inverse IP is a L and R swap after 16 rounds. There's enough information in that first image to produce an answer. – user16145658 Jan 08 '24 at 21:25
  • ok thanks @user16145658 – Bassel 1000 Jan 10 '24 at 13:55

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