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general.py
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general.py
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# general key Encryption
def calc_inv_ind(ind):
n = [0]*len(ind)
for i, j in enumerate(ind):
n[j] = i
return n
def calc_permutation(ind, bs):
n = [0]*len(ind)
for i, j in enumerate(ind):
n[j] = bs[i]
return n
class EncException(Exception):
pass
class Encryption:
def forward(self, bs):
raise EncException("forward not implemented")
def backward(self, bs):
raise EncException("backward not implemented")
class Permutation(Encryption):
def __init__(self, ind):
assert set(ind) == set([i for i in range(len(ind))])
self.ind = ind
def forward(self, bs):
return calc_permutation(self.ind, bs)
def backward(self, bs):
inv_ind = calc_inv_ind(self.ind)
return calc_permutation(inv_ind, bs)
class Xor(Encryption):
def __init__(self, const):
self.const = const
def forward(self, bs):
n = []
for c, b in zip(self.const, bs):
n.append(c^b)
return n
def backward(self, bs):
return self.forward(bs) # backward is same as forward
class Rot(Encryption):
def __init__(self, rot):
self.rot = rot
def forward(self, bs):
return [bs[(i - self.rot) % len(bs)] for i in range(len(bs))]
def backward(self, bs):
return [bs[(i + self.rot) % len(bs)] for i in range(len(bs))]