The authentication device then generates, using {HEAD ~ the same code generation} algorithm, an expected code value based on a second secret key and compares the expected code value to {TAIL ~ the service authentication code} 
The authentication device then generates , using { HEAD ~ the same code generation } algorithm , an expected code value based on a second secret key and compares the expected code value to { TAIL ~ the service authentication code }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL