On Fri, Feb 23, 2024 at 03:41:40PM -0500, Stefan Berger wrote: > +static inline void ecc_digits_from_bytes(const u8 *in, unsigned int nbytes, > + u64 *out, unsigned int ndigits) > +{ > + unsigned int sz = ndigits << ECC_DIGITS_TO_BYTES_SHIFT; > + u8 tmp[ECC_MAX_DIGITS << ECC_DIGITS_TO_BYTES_SHIFT]; > + unsigned int o = sz - nbytes; > + > + memset(tmp, 0, o); > + memcpy(&tmp[o], in, nbytes); > + ecc_swap_digits(tmp, out, ndigits); > +} Copying the whole key into tmp seems inefficient. You only need special handling for the first few bytes of "in" (6 bytes in the P521 case) and could use ecc_swap_digits() to convert the rest of "in" directly to "out" without using tmp. So it would be sufficient to allocate the first digit on the stack, memset + memcpy, then convert that to native byte order into "in[0]" and use ecc_swap_digits() for the rest. And the special handling would be conditional on "!o", so is skipped for existing curves. Thanks, Lukas