# What is the key length of shared secret by Curve 25519 ECDH

Both parties uses Curve 25519 key pairs for ECDH key exchange. What is the key length of shared secret after ECDH?

• Hint: Of what type is a DH shared secret usually? How big is that type for Curve25519?
– SEJPM
May 11 '20 at 9:19
• @SEJPM: the standard 32-byte curve25519 for ecdh May 11 '20 at 9:29

{ $$q: q \in$${ $$0,1,...,2^{256 - 1}$$}}