Abstract. Multiplication is one of the most important finite field arithmetic operations in cryptographic computations. Dual basis multipliers over GF(2m) are widely applied in this kind of computations due to its advantage of small chip area. However, up to date, there are only few methods that can keep balance of low space complexity and low time complexity at the same time. To achieve such an efficient aim, this study presents a novel digit-serial dual basis multiplier that is different from existing ones with a modified cut-set method using Karatsuba algorithm. Though this kind of multiplier will lose some throughput, it needs only a small number of transistors so that it is particularly suitable for some hand held devices that equipped only limited resources. The proposed digit serial dual basis multiplier saves 54% space complexity and 30% time complexity as compared to existing similar studies with NIST suggested values for elliptic curve cryptosystem.