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As I understood in FEAL-4 it needs 4 pair of round keys. Which means that we need to launch Fk function 4 times.

My problem occurs starting the 2nd round. At the first round we have the original 64 bits key; which is sliced to 32 bits. So on the output of 1st round we have 32 bit key. But the 2nd, 3rd and 4th round also require a 64 bit key.

What should I do on the 2nd round? After the 1st round I have only 32 bit key. Does it means that 2nd part should be filled with 0's?

Maarten Bodewes
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nmZ
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1 Answers1

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From what I can tell about the FEAL family by doing a little bit of research, the inputs for the FK function are two 32-bit sub-keys, each of which are half of the 64-bit key.

http://www.cs.rit.edu/~ark/spring2013/482/team/g1/report.pdf

Contains some instruction on the FK function you are asking about.

Desthro
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