Cryptography: Theory and Practice:The Data Encryption Standard

Cryptography: Theory and Practice
by Douglas Stinson
CRC Press, CRC Press LLC
ISBN: 0849385210   Pub Date: 03/17/95  

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In the remainder of this section, we present the specific functions used in DES.

The initial permutation IP is as follows:

IP
58	50	42	34	26	18	10	2
60	52	44	36	28	20	12	4
62	54	46	38	30	22	14	6
64	56	48	40	32	24	16	8
57	49	41	33	25	17	9	1
59	51	43	35	27	19	11	3
61	53	45	37	29	21	13	5
63	55	47	39	31	23	15	7

This means that the 58th bit of x is the first bit of IP(x); the 50th bit of x is the second bit of IP(x), etc.

The inverse permutation IP^-1 is:

IP-1
40	8	48	16	56	24	64	32
39	7	47	15	55	23	63	31
38	6	46	14	54	22	62	30
37	5	45	13	53	21	61	29
36	4	44	12	52	20	60	28
35	3	43	11	51	19	59	27
34	2	42	10	50	18	58	26
33	1	41	9	49	17	57	25

The expansion function E is specified by the following table:

E bit-selection table
32	1	2	3	4	5
4	5	6	7	8	9
8	9	10	11	12	13
12	13	14	15	16	17
16	17	18	19	20	21
20	21	22	23	24	25
24	25	26	27	28	29
28	29	30	31	32	1

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