Curve 25519 is one of the most widely used ECC methods and is defined in [RFC 7748]. This page will take the two vectors defined in the RFC, and check the output. [secp256k1 barebones][P256 barebones][P521 barebones][Curve 25519 barebones]. With X25519, we have an input u-coordinate value (the x-value) and a scalar value, and we get an output u-coordinate. In this case we will compute a shared key for ECDH. The vectors are:
Alice's private key, a: 77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a Alice's public key, X25519(a, 9): 8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a Bob's private key, b: 5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb Bob's public key, X25519(b, 9): de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f Their shared secret, K: 4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742