(PHP 7 >= 7.2.0, PHP 8)
sodium_crypto_sign_ed25519_sk_to_curve25519 — Convert an Ed25519 secret key to a Curve25519 secret key
Given an Ed25519 secret key, calculate the birationally equivalent X25519 secret key.
secret_keySecret key suitable for the crypto_sign functions.
Secret key suitable for the crypto_box functions.