Data Sheet

Chips and readers- USER’S GUIDE
UG 23
Version 1.0
ALGORITHMS
KEY PERMUTATION
Proceed as described below to permute a key.
Example: Permute the key K
ex
.
Kex = 0x5C 0xBC 0xF1 0xDA 0x45 0xD5 0xFB 0x5F
(0x5F)
!
01011111
(0xFB)
!
11111011
(0xD5)
!
11010101
(0x45)
!
01000101
(0xDA)
!
11011010
(0xF1)
!
11110001
(0xBC)
!
10111100
(0x5C)
!
01011100
&&&&&&&&
0x6E 0xFD 0x46 0xEF 0xCB 0xB3 0xC8 (0xF4)
0xF4 = 0B
Kexp = 0x6E 0xFD 0x46 0xEF 0xCB 0xB3 0xC8 0x0B
Replace the last byte by :
CHECKSUM BYTE CALCULATION
Proceed as described below to calculate a key checksum byte.
Note: the ⊕ symbol means a bit to bit x-or operation.
Example:
K = 0x5C 0xBC 0xF1 0xDA 0x45 0xD5 0xFB 0x5F
Kp = 0x6E 0xFD 0x46 0xEF 0xCB 0xB3 0xC8 0x0B
Checksum = 0x6E ⊕ 0xFD ⊕ 0x46 ⊕ 0xEF ⊕ 0xCB ⊕ 0xB3 ⊕ 0xC8 = 0x8A
Checksum = 0x8A = 0x75
and then,
K
x
p_chk = 0x6E 0xFD 0x46 0xEF 0xCB 0xB3 0xC8 0x75
LOAD KEY CHECKSUM CALCULATION
! Complete the 5 command bytes with 3 bytes 00 so to get 8 bytes
! Calculate RES = (Command bytes) ⊕ K
x
p.
! Calculate the checksum CHK = Most Significant 4-Bytes(RES) ⊕ Least Significant
4-Bytes(RES).