Multi-digit multiplication is widely used for various ap-plications in recent years, including numerical calculation, chaos arithmetic, primality testing. Systems with high per-formance and low energy consumption are demanded, es-pecially for image processing and communications with cryptography using chaos. In this paper, hardware design of multi-digit integer multiplication is described and its VLSI realization is evaluated in terms of the cost and per-formance. A version of Karatsuba hardware using 0.18µm process can perform 512-bit multiplications 30 times faster than software at the area cost of 6.91mm2. Computation energy was found to be nearly 10−3 of that consumed by general purpose processor which executes the software ver-sion. The results obtained by this study will help system designers for applications requiring multi-digit multiplica-tion to select design alternatives including ASIC realiza-tion.