Renamed from `rsa-decrypt', since the name was no longer appropriate.

[u/mdw/catacomb] / key.1

.\" -*-nroff-*-
.ie t \{\
.  ds ss \s8\u
.  ds se \d\s0
.\}
.el \{\
.  ds ss ^
.  ds se
.\}
.TH key 1 "5 June 1999" Catacomb
.SH NAME
key \- simple key management system
.SH SYNOPSIS
.B key
.RB [ \-k
.IR keyring ]
.I command
.PP
where
.I command
is one of:
.PP
.B add
.RB [ \-lq ]
.RB [ \-a
.IR alg ]
.RB [ \-b | \-B
.IR bits ]
.RB [ \-p
.IR param ]
.RB [ \-r
.IR tag ]
.br
\h'8n'
.RB [ \-e
.IR expire ]
.RB [ \-t
.IR tag ]
.RB [ \-c
.IR comment ]
.I type
.IR attr ...
.br
.B expire
.IR tag ...
.br
.B delete
.IR tag ...
.br
.B tag
.I tag
.RI [ new-tag ]
.br
.B comment
.I tag
.RI [ comment ]
.br
.B setattr
.I tag
.IR attr ...
.br
.B lock
.I qtag
.br
.B unlock
.I qtag
.br
.B list
.RB [ \-uqv ]
.RB [ \-f
.IR filter ]
.RI [ tag ...]
.br
.B fingerprint
.RB [ \-f
.IR filter ]
.RI [ tag ...]
.br
.B tidy
.br
.B extract
.RB [ \-f
.IR filter ]
.I file
.RI [ tag ...]
.br
.B merge
.I file
.SH DESCRIPTION
The
.B key
command performs useful operations on Catacomb keyring files.  It
provides a number of subcommands, by which the various operations may be
carried out.
.SS "Global options"
Before the command name,
.I "global options"
may be given.  The following global options are supported:
.TP
.B "\-h, \-\-help"
Writes a brief summary of
.BR key 's
various options to standard output, and
returns a successful exit status.
.TP
.B "\-v, \-\-version"
Writes the program's version number to standard output, and returns a
successful exit status.
.TP
.B "\-u, \-\-usage"
Writes a very terse command line summary to standard output, and returns
a successful exit status.
.TP
.BI "\-k, \-\-keyring " file
Names the keyring file which
.B key
is to process.  The default keyring, used if this option doesn't specify
one, is the file named
.B keyring
in the current directory.  The keyring must be stored in a regular file:
pipes, sockets, devices etc. are not allowed.
The
.B key
program attempts to lock the keyring before accessing it, using
.BR fcntl (2)
locking.  It will however time out after a short while (10 seconds) and
report a failure.
.SS Concepts
In addition to the actual key data itself, a Catacomb key has a number
of other pieces of information attached to it:
.TP
.B "keyid"
Every key has a 32-bit identifying number, written in hexadecimal.
Keyids are not actually related to the key contents: they're generated
randomly.  Applications use keyids to refer to specific keys; users are
probably better off with tags and types.  A
.I deleted
key cannot be looked up by keyid.
.TP
.B "tag"
A key's tag is a unique string which can be used by users and
applications to identify the key.  Tag strings may not contain spaces,
colons or dots.  A
.I deleted
key cannot be looked up by tag.  Whenever a tag name is wanted, a hex
keyid or key type string can be given instead.
.TP
.B "type"
A key's type string describes what the key may be used for.  The type
string is arbitrary, except that it may not contain whitespace
characters, dots or colons.  Applications use key types to obtain an
arbitrary but suitable key for some purpose.  An
.I expired
key cannot be looked up by type, but may be looked up by keyid or tag.
.TP
.B "key encoding"
There are a number of different ways in which keys can be represented,
according to the uses to which the key will be put.  Most symmetric
algorithms use
.I binary
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
.I structured
keys, which consist of a collection of named parts.  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
or
.B encrypt
(describing the key encoding);
.BR symmetric ,
.BR private ,
.B public
or
.B shared
(describing the category of key);
.B burn
and its negation
.B \-burn
(whether the key should be erased from memory after use); and
.B secret
and its negation
.B \-secret
(whether the key is safe to divulge).
.TP
.B "qualified tag"
A key component may be identified by the key's tag (or keyid, or type).
Subcomponents of structured keys are identified by following the tag by
a dot and the name of the subcomponent.
.TP
.B "expiry time"
Most keys expire after a certain amount of time.  Once a key has
expired, it will no longer be chosen as a result of a lookup by key
type.  However, it is not deleted until its deletion time is also
reached.
.TP
.B "deletion time"
A key's deletion time is the latest expiry time of any of the objects
which require that key.  For example, a key used for authenticating
cryptographic cookies should have its deletion time set to the longest
expiry time of any of the cookies it can authenticate.  Once a key's
deletion time is passed, it can no longer be referred to by
applications, and will be removed from the keyring next time it's
written to disk.
.TP
.B "comment"
A key may be given a comment when it's created.  The comment is for the
benefit of users, and isn't interpreted by applications at all.
(Hopefully.)
.TP
.B "attributes"
A key as zero or more name/value pairs.  The names and values are
arbitrary strings, except they may not contain null bytes.  Some
attributes may have meaning for particular applications or key types;
others may be assigned global meanings in future.
.SH "COMMAND REFERENCE"
.SS add
The
.B add
command creates a new key and adds it to the keyring.  The command
accepts the following options:
.TP
.BI "\-a, \-\-algorithm " alg
Selects a key generation algorithm.  The default algorithm is
.BR binary ;
the different algorithms are described below.
.TP
.BI "\-b, \-\-bits " bits
The length of the key to generate, in bits.  The default, if this option
is not supplied, depends on the key-generation algorithm.
.TP
.BI "\-B, \-\-qbits " bits
The length of the subsidiary key or parameter, in bits.  Not all
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.
.TP
.BI "\-e, \-\-expire " expire
The expiry date for the generated key.  This may be the string
.RB ` forever '
if the key should never expire automatically, or any date acceptable to
the
.BR getdate (3)
library function.  Briefly,
.B getdate
understands absolute dates such as
.RB ` 1999-08-02 '
or
.RB ` "August 2nd, 1999" ',
and (perhaps more usefully) relative dates such as
.RB ` "+2 weeks" '.
The default is to allow a 2 week expiry, which isn't useful.
.TP
.BI "\-c, \-\-comment " comment
Sets a comment for the key.  The default is not to attach a comment.
.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.
.TP
.BI "\-r, \-\-rand-id " tag
Selects the key to use for the random number generator.  Catacomb's
random number generator can be
.IR keyed ,
so that, even if the inputs to the generator are compromised, knowledge
of the key is also necessary to be able to predict the output.  By
default, the latest-expiring key with type
.B catacomb-rand
is used, if present; if not, no key is used.
.TP
.BI "\-l, \-\-lock"
Requests that the secret parts of the newly-generated key be encrypted
using a passphrase.
.TP
.BI "\-q, \-\-quiet"
Suppresses the progress indication which is usually generated while
time-consuming key generation tasks are being performed.
.PP
The key's type is given by the required
.I type
argument.  Following the type are zero or more attributes, which are
attached to the key in the same way as for the
.B setattr
command.
.PP
The key-generation algorithms supported are as follows:
.TP
.B "binary"
Generates a plain binary key of the requested length.  If the requested
key length is not a multiple of eight, the high-order bits of the first
octet of the key are zeroed.  The default key length is 128 bits.
.TP
.B "des"
Generates a DES key, with parity bits.  The key length must be 56, 112
or 168; the default is 56.  The low-order bit of each octet is ignored by
the DES algorithm; it is used to give each octet odd parity.
.TP
.B "rsa"
Generates a public/private key pair for use with the RSA algorithm.
.IP
The key components are
.I p
and
.IR q ,
a pair of prime numbers;
.IR n ,
the product of
.I p
and
.IR q ;
.IR e ,
the public exponent;
.IR d ,
the private exponent, chosen such that
.IR ed \ \(==\ 1
(mod
.RI ( p \ \-\ 1)( q \ \-\ 1));
and some other values useful for optimizing private-key operations:
.IR q \*(ss\-1\*(se\ mod\  p ,
.IR d \ mod\  p \ \-\ 1,
and
.IR d \ mod\  q \ \-\ 1.
The values
.I n
and
.I e
constitute the public key; the rest must be kept secret.  The key size
requested by the
.B \-b
option determines the size of the modulus
.IR n ;
the default is 1024 bits.
.IP
The key generation algorithm chooses
.I p
and
.I q
to be
.I strong
primes: both
.IR p \ \-\ 1
and
.IR p \ +\ 1
have large prime factors \- call them
.I r
and
.I s
respectively \- and
.IR r \ \-\ 1
also has a large prime factor;
.I q
has similar properties.
.IP
The modulus
.I n
cannot be sensibly used as a shared parameter, since knowledge of
corrssponding public and private exponents is sufficient to be able to
factor the modulus and recover other users' private keys.
.TP
.B "dh-params"
Generates parameters for use with the Diffie-Hellman key exchange
protocol, and many related systems, such as ElGamal encryption and
signatures, and even DSA (although the DSA algorithm is probably better
for this).  The parameters are a prime number
.IR q ,
a larger prime number
.IR p ,
and a generator
.I g
of the
.RI order- q
subgroup of the integers
.RI mod\  p .
.IP
The key size set by the
.B \-b
option determines the size of the modulus
.IR p ;
the size of the generator order
.I q
is set by the
.B \-B
option.  The default modulus size is 1024 bits; if no size is specified
for
.IR q ,
the parameters are chosen such that
.IR p \ =\ 2 q \ +\ 1,
and
.I
g
is assigned the value 4.  This takes much longer.
.IP
If used with the
.B \-p
option, the algorithm simply copies the parameters from an existing key.
.TP
.B "dh"
Generates a public/private key pair for use with offline Diffie-Hellman,
ElGamal, DSA or similar discrete-logarithm-based systems.  It selects a
private key
.IR x \ <\  q ,
and computes the public key
.IR y \ =\  g\*(ssx\*(se \ mod\  p .
.TP
.B "dsa-param"
Generates parameters for the DSA algorithm.  DSA parameters are also
suitable for use with Diffie-Hellman and ElGamal system.
.IP
The main difference between DSA and Diffie-Hellman parameter generation
is thatthe DSA parameter generation
algorithm creates a
.I seed
from which the parameters are derived, and, assuming that the SHA-1 hash
function is strong, it's not feasible to construct a seed from which
deliberately weak parameters are derived.  The algorithm used is the one
described in the DSA standard, FIPS\ 186, extended only to allow
sequential search for a prime
.I q
and to allow arbitrary parameter sizes.  The seed is stored,
Base64-encoded, as the value of the attribute
.BR seed .
.IP
The default lengths for
.I p
and
.I q
are 768 and 160 bits respectively, since the DSA standard specifies that
.I q
be 160 bits, and the choice of 768 bits for
.I p
gives commensurate security.
.TP
.B "dsa"
Generates a public/private key pair for DSA.  As for Diffie-Hellman
keys, it selects a
private key
.IR x \ <\  q ,
and computes the public key
.IR y \ =\  g\*(ssx\*(se \ mod\  p .
.TP
.B "bbs"
Generates a public/private key pair for the Blum-Blum-Shub random-number
generator, and the Blum-Goldwasser semantically-secure public-key
encryption system.
.IP
The key components are prime numbers
.I p
and
.IR q ,
both congruent to 3 (mod\ 4), and their product
.IR n .
The public key is simply the modulus
.IR n ;
the factors
.I p
and
.I q
are the private key.
.IP
The key-generation algorithm ensures that the two primes
.I p
and
.I q
are
.I strong
(see the discussion of strong primes above, in the section on RSA keys),
and that
.RI ( p \ \-\ 1)/2
and
.RI ( q \ \-\ 1)/2
are relatively prime, giving a maximum possible period length.
.IP
The key size requested by the
.B \-b
option determines the length of the modulus
.IR n ;
the default length is 1024 bits.
.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
their
.IR tag s.
.SS "delete"
Deletes keys immediately.  The keys to delete are listed by their
.IR tag s.
Be careful when deleting keys.  It might be a better idea
to expire keys rather than deleting them.
.SS "tag"
Sets, deletes or changes the tag attached to a key.  The first tag or
keyid names the key to be modified; the second, if present specifies the
new tag to be set.  If no second argument is given, the existing tag, if
any, is removed and no new tag is set.
.SS "setattr"
Attaches attributes to a key.  The key to which the attributes should be
attached is given by its
.IR tag .
Each attribute has the form
.IB name = value\fR.
An attribute can be deleted by assigning it an empty value.  Although
the keyring file format is capable of representing an attribute with an
empty value as distinct from a nonexistant attribute, this interface
does not allow empty attributes to be set.
.SS "comment"
Sets, deletes or changes the comment attached to a key.  The first
argument is a key tag or keyid which names the key to be modified; the
second, if present, is the new comment.  If no second argument is given,
the existing comment, if any, is removed, and no new comment is set.
.SS "lock"
Locks a key or key component using a passphrase.  If the key is already
locked, the existing passphrase is requested, and a new passphrase is
set.
.SS "unlock"
Unlocks a passphrase-locked key or key component.  If the key is not
locked, an error is reported.
.SS "list"
Lists the keys in the keyring.  A couple of options are supported:
.TP
.B "\-v, \-\-verbose"
Increases the amount of information displayed for each key.  Repeat for
a greater effect.
.TP
.B "\-q, \-\-quiet"
Decreases the amount of information displayed for each key.  Each use
cancels a
.RB ` \-v '
option.
.TP
.B "\-u, \-\-utc"
Display key expiry times as UTC rather than using the local time zone.
.TP
.BI "\-f, \-\-filter " filter
Specifies a filter.  Only keys and key components which match the filter
are listed.
.PP
By default, a single line of output is generated for each, showing
keyids, types, expiry and deletion dates, and comments.  Additional
.RB ` \-v '
options show more information, such as the exact time of day for expiry
and deletion, key attributes, and a dump of the actual key data.  If the
verbosity level is sufficiently high, passphrases are requested to
decrypt locked keys.  Make sure nobody is looking over your shoulder
when you do this!
.SS "fingerprint"
Reports a fingerprint (secure hash) on components of requested keys.
The following option is supported:
.TP
.BI "\-f, \-\-filter " filter
Specifies a filter.  Only keys and key components which match the filter
are fingerprinted.  The default is to only fingerprint nonsecret
components.
.PP
The keys to be fingerprinted are named by their tags or keyids given as
command line arguments.  If no key tags are given, all keys which match
the filter are fingerprinted.
.SS "tidy"
Simply reads the keyring from file and writes it back again.  This has
the effect of removing any deleted keys from the file.
.SS "extract"
Writes a selection of keys to a file.  An option is supported:
.TP
.BI "\-f, \-\-filter " filter
Specifies a filter.  Only keys and key components which match the filter
are written.
.PP
Keys extracted are written to the file named by the first argument,
which may be
.RB ` \- '
to designate standard output.  The keys to extract are listed by their
tags; if no tags are given, all keys which match the filter are
extracted.  The output is a valid keyring file.
.SS "merge"
Merges the keys from the named
.IR file ,
which may be
.RB ` \- '
to designate standard input, with the keyring.  Keys already in the
keyring are not overwritten: you must explicitly remove them first if
you want them to be replaced during the merge.
.SH "SEE ALSO"
.BR keyring (5).
.SH AUTHOR
Mark Wooding, <mdw@nsict.org>