'Return the private key blob for this key. The blob is the
over-the-wire format for private keys:
Specification in OpenSSH PROTOCOL.agent
RSA keys::
string \'ssh-rsa\'
integer n
integer e
integer d
integer u
integer p
integer q
DSA keys::
string \'ssh-dss\'
integer p
integer q
integer g
integer y
integer x
EC keys::
string \'ecdsa-sha2-[identifier]\'
integer x
integer y
integer privateValue
identifier is the NIST standard curve name.'

def privateBlob(self):

    type = self.type()
    data = self.data()
    if (type == 'RSA'):
        return ((((((common.NS('ssh-rsa') + common.MP(data['n'])) + common.MP(data['e'])) + common.MP(data['d'])) + common.MP(data['u'])) + common.MP(data['p'])) + common.MP(data['q']))
    elif (type == 'DSA'):
        return (((((common.NS('ssh-dss') + common.MP(data['p'])) + common.MP(data['q'])) + common.MP(data['g'])) + common.MP(data['y'])) + common.MP(data['x']))
    else:
        return (((common.NS(data['curve']) + common.MP(data['x'])) + common.MP(data['y'])) + common.MP(data['privateValue']))
