term% cat index.txt DSA(8) System Manager's Manual DSA(8)
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NAME
dsagen, asn12dsa, dsa2pub, dsa2ssh - generate and format dsa keys
SYNOPSIS
auth/dsagen [ -t tag ]
auth/asn12dsa [ -t tag ] [ file ]
auth/dsa2pub [ file ]
auth/dsa2ssh [ -c comment ] [ file ]
DESCRIPTION
Plan 9 represents a DSA (Digital Signature Algorithm) key as an attri‐
bute-value pair list prefixed with the string key; this is the generic
key format used by factotum(4). A full DSA private key has the follow‐
ing attributes:
proto must be dsa
!secret
decryption key
p modulus, a large prime
q group order, another large prime that divides p - 1.
alpha group generator
key $"alpha" sup secret ~ mod ~ p$
All the numbers are in hexadecimal. A DSA public key omits the at‐
tributes beginning with A key may have other attributes as well (for
example, a service attribute identifying how this key is typically
used), but to these utilities such attributes are merely comments.
For example, a private key and corresponding public key might look like
this (with [â¯] indicating elisions and \ marking line breaks for read‐
ability):
key proto=dsa p=D5[â¯]DB q=C2[â¯]E7 alpha=44[â¯]9B key=C1[â¯]3F \
!secret=9E[â¯]3B
key proto=dsa p=D5[â¯]DB q=C2[â¯]E7 alpha=44[â¯]9B key=C1[â¯]3F
Note that the order of the attributes does not matter.
Dsagen prints a randomly generated DSA private key whose n has exactly
nbits (default 1024) significant bits. If tag is specified, it is
printed between key and proto=dsa; typically, tag is a sequence of at‐
tribute-value comments describing the key.
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, insert‐
ing tag exactly as 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 ``DSA PRIVATE
KEY.'' The command:
auth/pemdecode 'DSA PRIVATE KEY' | auth/asn12dsa
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.
Dsa2pub reads a Plan 9 DSA public or private key, removes the private
attributes, and prints the resulting public key. Comment attributes
are preserved.
Dsa2ssh reads a Plan 9 DSA public or private key and prints the public
portion in the format used by SSH: and a long base-64 encoded number.
delim @@ For compatibility with external SSH implementations, the pub‐
lic keys in /sys/lib/ssh/keyring and $home/lib/keyring are stored in
this format.
EXAMPLES
Generate a fresh key and configure a remote Unix system to allow use of
that key for logins:
auth/dsagen -t 'service=ssh' >key
auth/dsa2ssh key | ssh unix 'cat >>.ssh/authorized_keys'
cat key >/mnt/factotum/ctl
ssh unix
SOURCE
/sys/src/cmd/auth
SEE ALSO
ssh(1), factotum(4), pem(8), rsa(8)
BUGS
There are too many key formats.
DSA(8)