Different keys. For example, you might currently be using a public/private keypair for 4096-bit RSA. That keypair (by definition) only works for the RSA key ex

Different keys. For example, you might currently be using a public/private keypair for 4096-bit RSA. That keypair (by definition) only works for the RSA key exchange algorithm. Likewise, an x22519 keypair is for the x25519 key exchange. A sntrup761x25519 keypair will be its own thing. As an aside, a sntrup761x25519 public key will be two public keys glued together (one for each algorithm). [1] Likewise for the private key. (one could reuse an existing x25519 keypair for the x25519 component of sntrup761x25519, but it seems like a bad idea) [1] https://github.com/openssh/openssh-portable/blob/master/kexsntrup761x25519.c#L42-L70 https://github.com/openssh/openssh-portable/blob/master/kexs...