gistfile1.txt

#!/usr/bin/env python

# With luck this illustrates 2 things r. keyczar
#  1. How to convert an RSA private key into a RSA public key.
#  2. How to convert RSA keys of either kind into their PEM
#     equivaletn.

import sys
try:
  import simplejson as json
except ImportError:
  import json
#from Crypto.PublicKey import RSA
import keyczar
from keyczar import keys
from keyczar import keyinfo
from keyczar import util
from pyasn1.codec.der import encoder
from pyasn1.type import univ
import base64

RSA_OID = univ.ObjectIdentifier('1.2.840.113549.1.1.1')

def makeRSAPublicFromPrivate(privateRSAKey):
  publicPortion = json.loads(str(privateRSAKey))['publicKey']
  publicRSAKey = keys.RsaPublicKey.Read(json.dumps(publicPortion))
  return publicRSAKey

def wrap_up_pem(kind, b64) :
  x = ["-----BEGIN " + kind + "-----"]
  for i in range(0,len(b64),64) :
    x.append("\n" + b64[i:i+64])
    x.append( '=' * (len(b64) % 4))
  x.append("\n-----END " + kind + "-----\n")
  return "".join(x)

def PublicRsaKey2PEM(params):
  oid = util.ASN1Sequence(RSA_OID, univ.Null())
  key = univ.Sequence()
  key.setComponentByPosition(0, univ.Integer(params['n']))
  key.setComponentByPosition(1, univ.Integer(params['e']))
  binkey = util.BytesToBin(encoder.encode(key))
  pubkey = univ.BitString("'%s'B" % binkey)
  seq = util.ASN1Sequence(oid, pubkey)
  return wrap_up_pem('PUBLIC KEY',
                     base64.standard_b64encode(encoder.encode(seq)))

def PrivateRsaKey2PEM(params):
  rsa_params =  ['n', 'e', 'd', 'p', 'q', 'dp', 'dq', 'invq']
  key = univ.Sequence()
  key.setComponentByPosition(0, univ.Integer(0)) # version
  for i in range(len(rsa_params)):
    key.setComponentByPosition(i+1, univ.Integer(params[rsa_params[i]]))
  return wrap_up_pem('RSA PRIVATE KEY',
                     base64.standard_b64encode(encoder.encode(key)))

def main():
    def p (x): sys.stdout.write(x)
    def h2 (x): p("\n\n====" + x + "===\n")

    newKey = keys.GenKey(keyinfo.RSA_PRIV,512)

    h2("Private JSON")
    p(str(newKey))

    h2("Public JSON")
    publicKey = makeRSAPublicFromPrivate(newKey)
    p(str(publicKey))

    h2("Private Key - PEM")
    def g(x) : return util.BytesToLong(x)
    def f(x) : return g(newKey.params[x])
    params = {'n' : g(newKey.public_key.params['modulus']),
              'e' : g(newKey.public_key.params['publicExponent']),
              'd' : f('privateExponent'),
              'p' : f('primeP'),
              'q' : f('primeQ'),
              'dp' : f('primeExponentP'),
              'dq' : f('primeExponentQ'),
              'invq' : f('crtCoefficient')}
    p(PrivateRsaKey2PEM(params))


    h2("Public Key - PEM")
    params = {'n' : g(newKey.public_key.params['modulus']),
              'e' : g(newKey.public_key.params['publicExponent']),}
    p(PublicRsaKey2PEM(params))

if __name__ == '__main__':
  main()