Security problems introduced with rapid increase in deployment of Internet-of-Things devices can be overcome only with lightweight cryptographic schemes and modules. A compact prime field (GF(p)) elliptic curve digital signature algorithm (ECDSA) engine suitable for use in such applications is presented. Generic architecture of the engine makes it suitable for other elliptic curve (EC) based schemes (EC Diffie–Hellman key exchange, EC integrated encryption, EC factoring etc.) with slight modifications. The presented engine is composed of a simple microcoded controller and application-specific processing units. It can work with ECs of up to 256 bits, while 160-bit ECDSA signature generation takes 490 K cycles. The engine is implemented as an intellectual property (IP) in a 180 nm process. However, its architecture allows it to be implemented on any application specific integrated circuit (ASIC) or FPGA platform with dual-port memory support. In view of its gate count of 11,366 gate equivalents, the presented work is the most compact ECDSA engine with capability for a wide range of curves and different applications.