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.TH key 1 "5 June 1999" "Straylight/Edgeware" "Catacomb cryptographic library"
.SH NAME
.IR tag ]
.RB [ \-c
.IR comment ]
+.RB [ \-C
+.IR curve ]
+.br
+\h'8n'
.I type
.IR attr ...
.br
keys. Keys used with number-theoretic systems (like most common
public-key systems) use
.I "multiprecision integer"
-keys. Algorithms which require several key constituents (again, like
-most public-key systems) use
+keys. Elliptic curve systems use
+.I "curve point"
+keys, which are either a pair of integers representing field elements,
+or a `point at infinity'. Algorithms which require several key
+constituents (again, like most public-key systems) use
.I structured
-keys, which consist of a collection of named parts. Finally, keys
-(including structured keys) can be encrypted.
+keys, which consist of a collection of named parts. It's possible to
+store an
+.I "ASCII string"
+as a key, though this is usually done as a component of a structured
+key. Finally, keys (including structured keys) can be encrypted.
.TP
.B "filter"
Keys and key components may be selected by a filter expression, a
sequence of flag names separated by commas. Flags are:
.BR binary ,
.BR integer ,
-.B struct
+.BR struct ,
+.BR ec ,
+.BR string ,
or
.B encrypt
(describing the key encoding);
.BR symmetric ,
.BR private ,
-.B public
+.BR public ,
or
.B shared
(describing the category of key);
.BI "\-c, \-\-comment " comment
Sets a comment for the key. The default is not to attach a comment.
.TP
+.BI "\-C, \-\-curve " curve-spec
+Use the elliptic curve described by
+.I curve-spec
+when generating elliptic curve parameters.
+.TP
.BI "\-t, \-\-tag " tag
Selects a tag string for the key. The default is not to set a tag. It
is an error to select a tag which already exists.
corrssponding public and private exponents is sufficient to be able to
factor the modulus and recover other users' private keys.
.TP
-.B "dh-params"
+.B "dh-param"
Generates parameters for use with the Diffie-Hellman key exchange
protocol, and many related systems, such as ElGamal encryption and
signatures, and even DSA. (The separate DSA algorithm uses the
.IR p \ =\ 2 q \ +\ 1,
with
.I q
-prime). In this case, the value of
+prime). Finding safe primes takes a very long time. In this case, the
+value of
.I g
is fixed as 4.
.IP
.I g
will generate the group of order
.RI ( p \ \-\ 1)/2\ =\ q \*(us0\*(ue\ q \*(us1\*(ue\ q \*(us2\*(ue\ ...
+.IP
+Finally, the
+.B \-C
+option can be given, in which case the parameters are taken directly
+from the provided group specification, which may either be the the name
+of one of the built-in groups (say
+.B "key add \-a dh\-param \-C list 42"
+for a list) or a triple
+.RI ( p ,\ q ,\ g ).
+separated by commas. No random generation is done in this case: the
+given parameters are simply stored.
.TP
.B "dh"
Generates a public/private key pair for use with offline Diffie-Hellman,
option determines the length of the modulus
.IR n ;
the default length is 1024 bits.
+.TP
+.B "ec-param"
+Store an elliptic curve specification. If no explicit
+.I curve-spec
+is given (the
+.RB ` \-C '
+option) then a curve is chosen whose order is about the size given by the
+.RB ` \-b '
+option (default is 256 bits).
+.IP
+A
+.I curve-spec
+can be given explicitly (in which case
+.RB ` \-b '
+is ignored). It can either be the name of a built-in curve (say
+.B "key add \-a ec\-param \-C list 42"
+for a list of curve names) or a full specification. The curve is
+checked for correctness and security according to the SEC1
+specification: failed checks cause a warning to be issued to standard
+error (though the program continues anyway). The check can be
+suppressed using the
+.RB ` \-q '
+option.
+.IP
+A curve specification consists of the following elements optionally
+separated by whitespace: a
+.IR "field type" ,
+which is one of
+.BR "prime" ,
+.BR "niceprime" ,
+.BR "binpoly" ,
+.or
+.BR "binnorm" ;
+an optional
+.RB ` : ';
+the field modulus
+.IR p ;
+if the field type is
+.B binnorm
+then an optional
+.RB ` , '
+and the representation of the normal element \*(*b; an optional
+.RB ` / ';
+a
+.IR "curve type" ,
+which is one of
+.BR "prime" ,
+.BR "primeproj" ,
+.BR "bin" ,
+and
+.BR "binproj"
+(the `proj' types currently have much better performance);
+an optional
+.RB ` : ';
+the two field-element parameters
+.I a
+and
+.IR b
+which define the elliptic curve
+.IR E ,
+separated by an optional
+.RB ` , ';
+an optional
+.RB ` / ';
+the
+.IR x -
+and
+.IR y -coordinates
+of the generator point
+.IR G ,
+separated by an optional
+.RB ` , ';
+an optional
+.RB ` : ';
+the order
+.I r
+of the group generated by
+.IR G ;
+an optional
+.RB ` * ';
+and the
+.I cofactor
+.I h
+=
+.RI # E / r .
+.TP
+.B "ec"
+Generate a private scalar and a corresponding public point on an
+elliptic curve. See
+.B ec-param
+above for how to specify elliptic curve parameter sets. The scalar
+.I x
+is chosen unformly between 0 and the curve order
+.IR r ;
+the public point is then
+.I x
+\(mu
+.IR G .
.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
projects / u / mdw / catacomb / blobdiff