'Yields a new random key ("ZjNmYTc4ZDk0MTkyYk...").'

@property
def key(self, pairs=('rA', 'aZ', 'gQ', 'hH', 'hG', 'aR', 'DD'), n=32):

    k = str(random.getrandbits(256))
    k = hashlib.sha256(k).hexdigest()
    k = base64.b64encode(k, random.choice(pairs)).rstrip('==')
    return k[:n]
