  Research in the area of secure multi-party computation with an unconventional
method of using a physical deck of playing cards began in 1989 when den Boar
proposed a protocol to compute the logical AND function using five cards. Since
then, the area has gained interest from many researchers and several card-based
protocols to compute various functions have been developed. In this paper, we
propose a card-based protocol called the overwriting protocol that can securely
compute the $k$-candidate $n$-variable equality function $f: \{0,1,\ldots
,k-1\}^n \rightarrow \{0,1\}$. We also apply the technique used in this
protocol to compute other similar functions.
