—Modular multiplication is the fundamental and compute-intense operation in many Public-Key crypto-systems. This paper presents two modular multipliers with their efficient architectures based on Booth encoding, higher-radix, and Montgomery powering ladder approaches. Montgomery powering ladder technique enables concurrent execution of main operations in the proposed designs, while higher-radix techniques have been adopted to reduce an iteration count which formally dictates a cycle count. It is also shown that by an adopting Booth encoding logic in the designs helps to reduce their area cost with a slight degradation in the maximum achievable frequencies. The proposed designs are implemented in Verilog HDL and synthesized targeting virtex-6 FPGA platform using Xilinx ISE 14.2 Design suite. The radix-4 multiplier computes a 256-bit modular