Efficient multiplications in finite fields of characteristics 5 and 7 are used for computing the Eta pairing over divisor class groups of the hyperelliptic curves Lee et al. (2008) . In this paper, using the recent methods for multiplication in finite fields, the explicit formulas for multiplication in F(5)5n and F(7)7n are obtained with 10 multiplications in F(5)n for F(5)5n and 15 multiplications in F(7)n for F(7)7n improving the results in Cenk and Ozbudak (2008) , Cenk et al. (2009) , Lee et al. (2008) [11 and Montgomery (2005) . The timing results of implementations of the Karatsuba type formulas and the proposed formula for multiplication in F(5)5.89 are given. (C) 2011 Elsevier B.V. All rights reserved.