## Cryptology ePrint Archive: Report 2021/804

A Note on Reduction Modulo $2^{448}-2^{224}-1$''

Timothy Shelton

Abstract: Nath and Sarkar propose algorithms to improve the efficiency of Diffie-Hellman key agreement using Curve448. In this note an error in the proof of correctness of the subtraction algorithm is described. An alternative argument is offered to fix this error without changing the algorithm or statement of correctness.

Category / Keywords: public-key cryptography / Curve448, Goldilocks prime, modulo reduction, elliptic curve cryptography, Diffie-Hellman key agreement