n2, n1 = encrypt(sbox, key, block2ns(iv))
gamma = []
for _ in xrange(0, len(data) + pad_size(len(data), BLOCKSIZE), BLOCKSIZE):
n2, n1 = encrypt(sbox, key, block2ns(iv))
gamma = []
for _ in xrange(0, len(data) + pad_size(len(data), BLOCKSIZE), BLOCKSIZE):