key-generation algorithms have a subsidiary key size.
.TP
.BI "\-p, \-\-parameters " tag
-Selects a key containing parameter values to copy. Not all
-key-generation algorithms allow the use of shared parameters. A new key
-also inherits attributes from its parameter key.
+Selects a key containing parameter values to copy.
+A new key also inherits attributes from its parameter key.
.TP
.BI "\-A, \-\-seedalg " seed-alg
Use the deterministic random number generator algorithm
.I x
\(mu
.IR G .
+.TP
+.B x25519
+Generate a private scalar and a corresponding public point on the
+(Montgomery-form) Curve25519 elliptic curve.
+The scalar is simply a random 256-bit string;
+the public key is the
+.IR x -coordinate
+of the corresponding point.
+.TP
+.B x448
+Generate a private scalar and a corresponding public point on the
+(Montgomery-form) Ed448-Goldilocks elliptic curve.
+The scalar is simply a random 256-bit string;
+the public key is the
+.IR x -coordinate
+of the corresponding point.
+.TP
+.B ed25519
+Generate a private key and a corresponding public point on the
+(twisted Edwards-form) Curve25519 elliptic curve.
+The private key is simply a random 256-bit string,
+from which a scalar and secret prefix are derived;
+the public key is the compressed form of the corresponding point.
+.TP
+.B empty
+Generate an empty key, with trivial contents.
+This is useful as a `parameters' key,
+carrying attributes to be applied to other keys
+if they don't require more detailed parameters.
.SS "expire"
Forces keys to immediately expire. An expired key is not chosen when a
program requests a key by its type. The keys to expire are listed by