.TH RSA 1
.SH NAME
dsagen, rsagen, rsafill, asn12dsa, asn12rsa, dsa2pub, rsa2csr, rsa2pub, dsa2ssh, rsa2ssh, rsa2x509 \- generate and format dsa and rsa keys
.SH SYNOPSIS
.PP
.B dsagen
[
.B -t
.I tag
]
.PP
.B rsagen
[
.B -b
.I nbits
]
[
.B -t
.I tag
]
.PP
.B rsafill
[
.I file
]
.PP
.B asn12dsa
[
.B -t
.I tag
]
[
.I file
]
.PP
.B asn12rsa
[
.B -t
.I tag
]
[
.I file
]
.PP
.B dsa2pub
[
.I file
]
.PP
.B rsa2pub
[
.I file
]
.PP
.B dsa2ssh
[
.I file
]
.PP
.B rsa2ssh
[
.B -2
]
[
.I file
]
.PP
.B rsa2x509
[
.B -e
.I expiretime
]
.I certinfo
[
.I file
]
.PP
.B rsa2csr
.I certinfo
[
.I file
]
.SH DESCRIPTION
Plan 9 represents DSA and RSA keys as attribute-value pair lists
prefixed with the string
.BR key ;
this is the generic key format used by
.IR factotum (4).
A full DSA private key has the following attributes:
.TP
.B proto
must be
.B dsa
.TP
.B p
prime public modulus
.TP
.B q
prime group order; divides
.BR p -1
.TP
.B alpha
group generator
.TP
.B key
.BR alpha ^ !secret
mod
.B p
.TP
.B !secret
the secret exponent
.PD
.PP
A full RSA private key has the following attributes:
.TP
.B proto
must be
.B rsa
.TP
.B size
the number of significant bits in
.B n
.TP
.B ek
the encryption exponent
.TP
.B n
the product of
.B !p
and
.B !q
.TP
.B !dk
the decryption exponent
.TP
.B !p
a large prime
.TP
.B !q
another large prime
.TP
.B "!kp\fR, \fL!kq\fR, \fL!c2
parameters derived from the other attributes, cached to speed decryption
.PD
.LP
All the numbers in both keys are in hexadecimal except RSA's
.I size ,
which is decimal.
A public key omits the attributes beginning with
.L ! .
A key may have other attributes as well (for example, a
.B service
attribute identifying how this key is typically used),
but to these utilities such attributes are merely comments.
.PP
For example, a very small (and thus insecure) private key and corresponding
public key might be:
.IP
.EX
key proto=rsa size=8 ek=7 n=8F !dk=67 !p=B !q=D !kp=3 !kq=7 !c2=6
key proto=rsa size=8 ek=7 n=8F
.EE
.LP
Note that the order of the attributes does not matter.
.PP
.I Dsagen
prints a randomly generated DSA private key using the 
NIST-recommended algorithm.
If
.I tag
is specified, it is printed between
.B key
and
.BR proto=dsa ;
typically,
.I tag
is a sequence of attribute-value comments describing the key.
.PP
.I Rsagen
prints a randomly generated RSA private key
whose
.B n
has exactly
.I nbits
(default 1024)
significant bits.
.PP
.I Rsafill
reads a private key,
recomputes the
.BR !kp ,
.BR !kq ,
and
.BR !c2
attributes if they are missing,
and prints a full key.
.PP
.I Asn12dsa
reads an DSA private key stored as ASN.1
encoded in the binary Distinguished Encoding Rules (DER)
and prints a Plan 9 DSA key,
inserting
.I tag
exactly as
.I dsagen
does.
ASN.1/DER is a popular key format on Unix and Windows;
it is often encoded in text form using the Privacy Enhanced Mail (PEM) format
in a section labeled as an
.RB `` DSA
.B PRIVATE
.BR KEY .''
The command:
.IP
.EX
pemdecode 'DSA PRIVATE KEY' | asn12dsa
.EE
.LP
extracts the key section from a textual ASN.1/DER/PEM key
into binary ASN.1/DER format and then
converts it to a Plan 9 DSA key.
.PP
.I Asn12rsa
is similar but operates on RSA keys.
.PP
.I Dsa2pub
reads a Plan 9 DSA public or private key,
removes the private attributes, and prints the resulting public key.
Comment attribtes are preserved.
.PP
.I Rsa2pub
is similar but operates on RSA keys.
.PP
.I Dsa2ssh
reads a Plan 9 DSA public or private key and prints the 
public portion in the format used by SSH version 2 (version 1 did not support DSA).
If the key has a 
.B comment
attribute, that comment is appended to the key.
.PP
.I Rsa2ssh
is similar but operates on RSA keys.
It decides whether to print in version 1 or version 2 
format by inspecting the
.B service
attribute.
.PP
.I Dsa2ssh
and
.I rsa2ssh
are useful for generating SSH's 
.B authorized_keys
file.
.PP
.I Rsa2x509
reads a Plan 9 RSA private key and writes a self-signed X.509 certificate
encoded in ASN.1/DER format to standard output.
(Note that ASN.1/DER X.509 certificates are different from ASN.1/DER private keys).
The certificate uses the current time as its start time and expires
.I expiretime
seconds
(default 3 years)
later.
It contains the public half of the key
and includes
.I certinfo
as the issuer/subject string (also known as a ``Distinguished Name'').
This info is typically in the form:
.IP
.EX
C=US ST=NJ L=07974 O=Lucent OU='Bell Labs' CN=G.R.Emlin
.EE
.LP
The X.509 ASN.1/DER format is often encoded in text using a PEM section
labeled as a
.RB `` CERTIFICATE .''
The command:
.IP
.EX
rsa2x509 'C=US OU=''Bell Labs''' file |
pemencode CERTIFICATE
.EE
.LP
generates such a textual certificate.
Applications that serve TLS-encrypted sessions
typically expect certificates in ASN.1/DER/PEM format.
.PP
.I Rsa2csr
is like
.I rsa2x509
but writes an X.509 certificate request.
.SH EXAMPLES
Generate a fresh key and use it to start the Plan 9 TLS-enabled web server:
.IP
.EX
rsagen -t 'service=tls owner=*' >key
rsa2x509 'C=US CN=*.cs.bell-labs.com' key |
	pemencode CERTIFICATE >cert
cat key >/mnt/factotum/ctl
ip/httpd/httpd -c cert
.EE
.PP
Generate a fresh set of SSH keys (only one is necessary),
load them into factotum,
and configure a remote Unix system to allow those keys for logins:
.IP
.EX
rsagen -t 'service=ssh role=decrypt' >rsa1
rsagen -t 'service=ssh-rsa role=sign' >rsa2
dsagen -t 'service=ssh-dss role=sign' >dsa2
.EE
.PP
Convert existing Unix SSH version 2 keys instead of generating new ones:
.IP
.EX
cd $HOME/.ssh
pemdecode 'DSA PRIVATE KEY' id_dsa | asn12dsa >dsa2
pemdecode 'RSA PRIVATE KEY' id_rsa | asn12rsa >rsa2
.EE
.PP
Load those keys into factotum:
.IP
.EX
cat rsa1 rsa2 dsa2 | 9p write -l factotum/ctl
.EE
Allow use of those keys for logins on other systems:
.IP
.EX
rsa2ssh rsa1 >auth.keys
rsa2ssh rsa2 >>auth.keys
dsa2ssh dsa2 >>auth.keys
scp auth.keys unix:.ssh/authorized_keys
.EE
.SH SOURCE
.B \*9/src/cmd/auth
.SH "SEE ALSO
.IR factotum (4),
.IR pem (1),
.IR ssh (1)
.SH BUGS
There are too many key formats.
.PP
There is no program to convert SSH version 1 RSA private keys.