Jython code to generation DSA/RSA keys

gistfile1.py

"""
Simple stupid utility to create RSA or DSA key keys

Just add the JSCH library to your classpath and things ought to work.

(JY25)~/Downloads > export CLASSPATH=./jsch-0.1.42.jar 
(JY25)~/Downloads > jython
*sys-package-mgr*: processing new jar, '/Users/victorng/Downloads/jsch-0.1.42.jar'
Jython 2.5.2 (Release_2_5_2:7206, Mar 2 2011, 23:12:06) 
[Java HotSpot(TM) 64-Bit Server VM (Apple Inc.)] on java1.6.0_29
Type "help", "copyright", "credits" or "license" for more information.
>>> from com.jcraft.jsch import KeyPair, JSch
>>> JSch
<type 'com.jcraft.jsch.JSch'>
>>> 
"""
import argparse
from com.jcraft.jsch import KeyPair, JSch
import sys

def parse_args():
    parser = argparse.ArgumentParser(description="Generate public/private keys")
    parser.add_argument('-crypt', 
            choices=('rsa', 'dsa'),
            required=True, 
            help="Crypto algorithm to use")

    parser.add_argument('-o', 
            type=argparse.FileType('w'),
            required=True, 
            help="Output file")

    parser.add_argument('-m', 
            type=str,
            required=True, 
            help="Key comment")

    return parser.parse_args()

def error_out():
    print """
usage: java KeyGen -crypt rsa -o output_keyfile -m comment
       java KeyGen -crypt dsa -o output_keyfile -m comment
    """
    sys.exit(-1)

if __name__ == '__main__':

    args = parse_args()

    typemap = {'rsa': KeyPair.RSA,
               'dsa': KeyPair.DSA,}


    keytype = typemap[args.crypt]

    filename = args.o.name
    args.o.close()
    comment = args.m

    jsch = JSch()

    passphrase = raw_input("Enter passphrase: ").strip()
    kpair = KeyPair.genKeyPair(jsch, keytype)
    kpair.setPassphrase(passphrase)
    kpair.writePrivateKey(filename)
    kpair.writePublicKey(filename+".pub", comment)

    print "Finger print: %s" % kpair.getFingerPrint()
    kpair.dispose()
    print "Private key is at: %s" % filename
    print "Public  key is at: %s.pub" % filename