ACR1255U-J1 – Reference Manual
Version V1.01
www.acs.com.hk
Page 31 of 73
5.7.4.
SPH_to_RDR_AuthRsp
This command is the second phase of the authentication process. After the device has initiated the
SPH_to_RDR_ReqAuth command to the ACR1255U-J1, the reader will then provide an
RDR_to_SPH_AuthRsp1 message if there’s no error.
The RDR_to_SPH_AuthRsp1 will contain a sequence of 16-byte random numbers encrypted using
the Customer Master Key. The paired key-generating device should decrypt it using the correct
Customer Master Key and pads it to the end of the 16-byte of random numbers. The overall 32-byte
random numbers will be decrypted using the Customer Master Key and returned to ACR1255U-J1
using this command in order to have a successful authentication.
Offset
Field
Size
Value
Description
Encrypted
0
bMessageType
1
6Bh
-
No
1
LEN1 LEN2
(wLength)
2
0025h
The Number of extra
bytes in the abAuthData
field, and is expressed in
two bytes long, and
LEN1 is MSB while
LEN2 is LSB;
No
3
Slot Number
1
00h
-
No
4
Sequence
1
00h
-
No
5
Parameter
1
00h
Slot Status
No
6
wCheckSum
1
wCheckSum means the
XOR values of all bytes
in the command
No
7
abAuthData
37
E0 00 00 46
00 + 32 bytes
random
number
abAuthData[0:15] – 16
bytes of random number
generated by the data
processing server
abAuthData[16:31] – 16
bytes of decrypted
random number
received from
ACR1255U-J1
All the 32 bytes of data
underwent a decryption
process with the
Customer Master Key
using AES128 CBC
cipher mode.
“E0 00 00 46 00” does
not need to be
decrypted.
Yes
The response to this message is RDR_to_SPH_AuthRsp2 if the command message received is error-
free and the random number generated returned by paired device is correct. Otherwise, the response
message will be RDR_to_SPH_ACK to provide the error information.
