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jarkko

Jarkko Sakkinen

Edited 5 months ago

Why Curve25519 uses EdDSA for signing, and SECP-P256-R1 and SECP-P256-K1 use ECDSA?

It’s the scale. Curve25519 field has the size that fits within 255 bits, and two previous have the size that fits within 256 bits.

So from that follows:

  • a new signature formalization is needed to reach similar or better results.
  • given the smaller size it can only reach this goal by integrating tightly to the choices of the finite field parameters.

There is formal backing for this but pure common sense it is exactly like “if loose some, you must gain some” ;-)

#cryptography #note

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