private static XECPublicKey deserializePublicKey(byte[] enc) {
        return KeyUtils.fromRawX25519PublicKey(enc);
    }
KEM implementation using Diffie-Hellman over X25519 curves as the shared
secret deriver and HKDF-SHA256 as its key derivation function.

HPKE KEM spec: DHKEM(X25519, HKDF-SHA256)

@author vekterli
security-utils/src/main/java/com/yahoo/security/hpke/DHKemX25519HkdfSha256.java