Paper 2015/343

High-speed Curve25519 on 8-bit, 16-bit, and 32-bit microcontrollers

Michael Düll and Björn Haase and Gesine Hinterwälder and Michael Hutter and Christof Paar and Ana Helena Sánchez and Peter Schwabe

Abstract

This paper presents new speed records for 128-bit secure elliptic-curve Diffie-Hellman key-exchange software on three different popular microcontroller architectures. We consider a 255-bit curve proposed by Bernstein known as Curve25519, which has also been adopted by the IETF. We optimize the X25519 key-exchange protocol proposed by Bernstein in 2006 for AVR ATmega 8-bit microcontrollers, MSP430X 16-bit microcontrollers, and for ARM Cortex-M0 32-bit microcontrollers. Our software for the AVR takes only 13 900 397 cycles for the computation of a Diffe-Hellman shared secret, and is the first to perform this computation in less than a second if clocked at 16 MHz for a security level of 128 bits. Our MSP430X software computes a shared secret in 5 301 792 cycles on MSP430X microcontrollers that have a 32-bit hardware multiplier and in 7 933 296 cycles on MSP430X microcontrollers that have a 16-bit multiplier. It thus outperforms previous constant-time ECDH software at the 128-bit security level on the MSP430X by more than a factor of 1.2 and 1.15, respectively. Our implementation on the Cortex-M0 runs in only 3 589 850 cycles and outperforms previous 128-bit secure ECDH software by a factor of 3.

Note: Typo in the abstract.