code: func GenerateKeyPair(passphrase string) ([]byte, []byte, error) {
  	priv, err := rsa.GenerateKey(rand.Reader, teleport.RSAKeySize)
  	if err != nil {
  		return nil, nil, err
  	}
  	privDer := x509.MarshalPKCS1PrivateKey(priv)
  	privBlock := pem.Block{
  		Type:    "RSA PRIVATE KEY",
  		Headers: nil,
  		Bytes:   privDer,
  	}
  	privPem := pem.EncodeToMemory(&privBlock)
  
  	pub, err := ssh.NewPublicKey(&priv.PublicKey)
  	if err != nil {
  		return nil, nil, err
  	}
  	pubBytes := ssh.MarshalAuthorizedKey(pub)
  	return privPem, pubBytes, nil
  }
docs: // GenerateKeyPair returns fresh priv/pub keypair, takes about 300ms to
  // execute.