The answer seems quite simple. Rather than general authentication as Anonymous Coward suggests above, which is more suitable for open-ended transaction processing than a one-off event which has other constraints, have a registration process (open during the whole match). Each person would enter his or her e-mail address only. Because each move is constrained to a 24-hour period, the organiser could send out a computer-generated password (say 12 characters in length) to each registered e-mail address to be used during the next 24 hour period. OK, a person can still sign on to several e-mail accounts to use the appropriate password each day but if they wish to do this, good on them! It would also deter attempts to use friends' and others' e-mail addresses.
Slashdot Mirror
The answer seems quite simple. Rather than general authentication as Anonymous Coward suggests above, which is more suitable for open-ended transaction processing than a one-off event which has other constraints, have a registration process (open during the whole match). Each person would enter his or her e-mail address only. Because each move is constrained to a 24-hour period, the organiser could send out a computer-generated password (say 12 characters in length) to each registered e-mail address to be used during the next 24 hour period. OK, a person can still sign on to several e-mail accounts to use the appropriate password each day but if they wish to do this, good on them! It would also deter attempts to use friends' and others' e-mail addresses.