5.1 DES: Key

The respective keys K_i , 1 <= i <= 16, are all derived from K. K consists of 56 bits, whereas the single keys are K_i  48 bit long.

The calculation is done in the following steps:

1.	K is extended with eigth parity bits on every 8th position to 64 bits and then passed to PC-1.
2.	The permutation PC-1 (PC = permuted choice) exchanges these bits in the following scheme to 56 bits, in which process the parity bits are removed again:	57	49	41	33	25	17	9
		1	58	50	42	34	26	18
		10	2	59	51	43	35	27
		19	11	3	60	52	44	36
		63	55	47	39	31	23	15
		7	62	54	46	38	30	22
		14	6	61	53	45	37	29
		21	13	5	28	20	12	4
3.	The result (PC-1)(K) is divided up in C0  and D0  of 28 bits each.
4.	Ci  and Di  with i = 1,...,16 are then calculated with Ci = LSi (Ci-1)  or   Di = LSi (Di-1) , where LSi  is a circular left-shift by the number of positions from the following table:

	Iteration i	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
	# Shifts	1	1	2	2	2	2	2	2	1	2	2	2	2	2	2	1

5.	The keys Ki  with i = 1,...,16 are then determied by Ki  = (PC-2)(Ci ,Di ), where the permutation PC-2 is depicted in the table on the right:	14	17	11	24	1	57
		3	28	15	6	21	10
		23	19	12	4	26	8
		16	7	27	20	13	2
		41	52	31	37	47	55
		30	40	51	45	33	48
		44	49	39	56	34	53
		46	42	50	36	29	32

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AES