In step 203, {HEAD ~ the signature key generator} 123 uses a hashing function to generate a signature key for {TAIL ~ the fingerprint} 
In step 203 , { HEAD ~ the signature key generator } 123 uses a hashing function to generate a signature key for { TAIL ~ the fingerprint }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL