Internet Security - Dang Thanh Binh's Page

The final decrypted plaintext is:
b267af31 6d8a59e7 b16ac385 f2a072be
SYMMETRIC BLOCK CIPHERS 105
Example 3.20 Consider RC6-32/20/24. Suppose the plaintext and user key are given
as follows:
Plaintext: 35241302 79685746 bdac9b8a f1e0dfce
User key: 01 23 45 67 89 ab cd ef
01 12 23 34 45 56 67 78
89 9a ab bc cd de ef f0
The user supplies a key of b = 24 bytes, where 0 ≤ b ≤ 255. Fromthiskey,2r + 4 = 44
words are derived and stored in the array S[0, 1,...,2r + 3]. This array is used in both
encryption and decryption.
Key array
S[0] = 4d80ade S[1] = c85296a3 S[2] = c7ca853c S[3] = d665bea0
S[4] = 4d34492f S[5] = e110bf65 S[6] = 9f4acf83 S[7] = ed85cb10
S[8] = f9f0f8eb S[9] = 2275ea3f S[10] = e5dc8714 S[11] = a1b4b8b4
S[12] = 1a28cd0a S[13] = 618fbe87 S[14] = 6fc1ede0 S[15] = 8eaf634d
S[16] = 7d213901 S[17] = bed7ab73 S[18] = 79ba092e S[19] = 6179bc8a
S[20] = aa35b6f6 S[21] = 0091b3ca S[22] = 65f970e9 S[23] = 687e9e94
S[24] = f17e5188 S[25] = 7ec55cf7 S[26] = fe2c8e93 S[27] = 2e7b3dae
S[28] = 56093cb8 S[29] = ed28fa03 S[30] = ab2eaaec S[31] = d049366f
S[32] = fcd4cbd3 S[33] = 84b3906f S[34] = 8eced9f1 S[35] = e02a2453
S[36] = 123b6e03 S[37] = a6192a81 S[38] = 8648252c S[39] = b29fbd04
S[40] = 735d2dc1 S[41] = 97447b58 S[42] = 362b46b2 S[43] = 7c310342
RC6 works with four 32-bit registers A, B, C and D which contain the initial input
plaintext as well as the output ciphertext at the end of encryption. Both encryption and
decryption using RC6-32/20/24 are processed as shown below.
Initial values in registers:
A = 35241302 B = 79685746
C = bdac9b8a D = f1e0dfce
Encryption with RC6-32/20/24
Round A B C D
0 35241302 7e406224 bdac9b8a ba337671
1 7e406224 bf73145b ba337671 ae7fec22
2 bf73145b 8223f9cc ae7fec22 d96ddcb2
3 8223f9cc 823d1be2 d96ddcb2 8ad786e7
4 823d1be2 30fa9e1e 8ad786e7 3439983d