As enterprises embrace blockchain technology, many real-world applications have been developed and deployed using permissioned blockchain platforms (access to network is controlled and given to only nodes with known identities). Such blockchain platforms heavily depend on cryptography to provide a layer of trust within the network, thus verification of cryptographic signatures often becomes the bottleneck. The Elliptic Curve Digital Signature Algorithm (ECDSA) is the most commonly used cryptographic scheme in permissioned blockchains. In this paper, we propose an efficient implementation of ECDSA signature verification on an FPGA, in order to improve the performance of permissioned blockchains that aim to use FPGA-based hardware accelerators. We propose several optimizations for modular arithmetic (e.g., custom multipliers and fast modular reduction) and point arithmetic (e.g., reduced number of point double and addition operations, and optimal width NAF representation). Based on these optimized modular and point arithmetic modules, we propose an ECDSA verification engine that can be used by any application for fast verification of ECDSA signatures. We further optimize our ECDSA verification engine for Hyperledger Fabric (one of the most widely used permissioned blockchain platforms) by moving carefully selected operations to a precomputation block, thus simplifying the critical path of ECDSA signature verification. From our implementation on Xilinx Alveo U250 accelerator board with target frequency of 250MHz, our ECDSA verification engine can perform a single verification in $760μs$ resulting in a throughput of 1,315 verifications per second, which is ~2.5x faster than state-of-the-art FPGA-based implementations. Our Hyperledger Fabric-specific ECDSA engine can perform a single verification in $368μs$ with a throughput of 2,717 verifications per second.