  This paper presents the first hardware implementation of the Datagram
Transport Layer Security (DTLS) protocol to enable end-to-end security for the
Internet of Things (IoT). A key component of this design is a reconfigurable
prime field elliptic curve cryptography (ECC) accelerator, which is 238x and 9x
more energy-efficient compared to software and state-of-the-art hardware
respectively. Our full hardware implementation of the DTLS 1.3 protocol
provides 438x improvement in energy-efficiency over software, along with code
size and data memory usage as low as 8 KB and 3 KB respectively. The
cryptographic accelerators are coupled with an on-chip low-power RISC-V
processor to benchmark applications beyond DTLS with up to two orders of
magnitude energy savings. The test chip, fabricated in 65 nm CMOS, demonstrates
hardware-accelerated DTLS sessions while consuming 44.08 uJ per handshake, and
0.89 nJ per byte of encrypted data at 16 MHz and 0.8 V.
