p261: A Karatsuba-Friendly Prime for Fast Elliptic Curve Arithmetic
摘要
We point to the cryptographic significance of the overlooked prime \(\texttt {p261} = 2^{261}-2^{131}-1\) . We explain our motivation behind searching for such a prime. We present cryptographically secure elliptic curves over \(GF(\texttt {p261})\) . We provide our speed oriented implementation of variable-base variable-scalar elliptic curve scalar multiplication using the Montgomery ladder. In this setting, a single scalar multiplication implemented with AVX2 instructions takes 85738 cycles on a Skylake 6500U processor.