from math import ceil
from urllib2 import quote, unquote
from base64 import b64encode as b64enc

class Lazarus():
    def __init__(self, key):
        self.key = key
        self.BS = 16
        self.iv = "0"*self.BS

    def enc(self, plaintext):
        t = quote(plaintext)
        prevBlock = self.iv
        c = ""
        for i in range(int(ceil(float(len(t))/self.BS))):
            block = t[i*self.BS:][:self.BS]
            prevBlock=self._sxor(self._rc4(block),prevBlock)
            c+=prevBlock
        return c

    def dec(self, ciphertext):
        c = ciphertext
        prevBlock = self.iv
        t = ""
        for i in range(int(ceil(float(len(c))/self.BS))):
            block = c[i*self.BS:][:self.BS]
            t+=self._rc4(self._sxor(block,prevBlock))
            prevBlock = block
        return unquote(t)

    def _sxor(self, s1, s2):
        return ''.join(chr(ord(a) ^ ord(b)) for a,b in zip(s1,s2))

    def _rc4(self, data):
        box = list(range(256))
        x = 0
        for i in range(256):
            x = (x + box[i] + ord(self.key[i % len(self.key)])) % 256
            box[i], box[x] = box[x], box[i]
        x = 0
        y = 0
        out = []
        for char in data:
            x = (x + 1) % 256
            y = (y + box[x]) % 256
            box[x], box[y] = box[y], box[x]
            out.append(chr(ord(char) ^ box[(box[x] + box[y]) % 256]))
        return ''.join(out)