rsagen, rsafill, asn12rsa, rsa2pub, rsa2ssh, rsa2x509 – generate and format rsa keys

auth/rsagen [ –b nbits ] [ –t tag ]

auth/rsafill [ file ]

auth/asn12rsa [ –t tag ] [ file ]

auth/rsa2pub [ file ]

auth/rsa2ssh [ file ]

auth/rsa2x509 [ –e expiretime ] certinfo [ file ]

Plan 9 represents an RSA key as an attribute–value pair list prefixed with the string key; this is the generic key format used by factotum(4). A full RSA private key has the following attributes:
proto   must be rsa
the number of significant bits in n
the encryption exponent
n       the product of !p and !q
the decryption exponent
!p      a large prime
!q      another large prime
!kp, !kq, !c2
parameters derived from the other attributes, cached to speed decryption

All the numbers are in hexadecimal except size, which is decimal. An RSA public key omits the attributes 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 very small (and thus insecure) private key and corresponding public key might be:
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

Note that the order of the attributes does not matter.

Rsagen prints a randomly generated RSA private key whose n has exactly nbits (default 1024) significant bits. If tag is specified, it is printed between key and proto=rsa; typically, tag is a sequence of attribute–value comments describing the key.

Rsafill reads a private key, recomputes the !kp, !kq, and !c2 attributes if they are missing, and prints a full key.

Asn12rsa reads an RSA private key stored as ASN.1 encoded in the binary Distinguished Encoding Rules (DER) and prints a Plan 9 RSA key, inserting tag exactly as rsagen 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 ``RSA PRIVATE KEY.'' The command:
auth/pemdecode 'RSA PRIVATE KEY' | auth/asn12rsa

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 RSA key.

Rsa2pub reads a Plan 9 RSA public or private key, removes the private attributes, and prints the resulting public key. Comment attributes are preserved.

Rsa2ssh reads a Plan 9 RSA public or private key and prints the public portion in the format used by SSH: three space–separated decimal numbers size, ek, and n. For compatibility with external SSH implementations, the public keys in /sys/lib/ssh/keyring and $home/lib/keyring are stored in this format.

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 expiretime seconds (default 3 years) later. It contains the public half of the key and includes certinfo as the issuer/subject string (also known as a ``Distinguished Name''). This info is typically in the form:
C=US ST=NJ L=07974 O=Lucent OU='Bell Labs' CN=G.R.Emlin

The X.509 ASN.1/DER format is often encoded in text using a PEM section labeled as a ``CERTIFICATE.'' The command:
auth/rsa2x509 'C=US OU=''Bell Labs''' file |
auth/pemencode CERTIFICATE

generates such a textual certificate. Applications that serve TLS–encrypted sessions (for example, httpd(8), pop3(8), and tlssrv(8)) expect certificates in ASN.1/DER/PEM format.

Generate a fresh key and use it to start a TLS–enabled web server:
auth/rsagen –t 'service=tls owner=*' >key
auth/rsa2x509 'C=US CN=*.cs.bell–' key |
auth/pemencode CERTIFICATE >cert
cat key >/mnt/factotum/ctl
ip/httpd/httpd –c cert

Generate a fresh key and configure a remote Unix system to allow use of that key for logins:
auth/rsagen –t 'service=ssh' >key
auth/rsa2ssh key | ssh unix 'cat >>.ssh/authorized_keys'
cat key >/mnt/factotum/ctl
ssh unix


ssh(1), factotum(4), dsa(8), pem(8)

There are too many key formats.
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