def OFB(text, key, init_vector, nbits, decrypt=False):
'''
nbits: encryption length
'''
if 256 % nbits != 0:
raise Exception('Length of nbits must be a factor of 256!')
fullbits = text_to_bits(text)
pea = PEA(key)
qbits = init_vector
bits_encrypt = []
for i in range(int(len(fullbits) / nbits)):
if not decrypt:
bits = fullbits[(i * nbits):((i + 1) * nbits)]
enc_res = pea.encrypt(qbits, False)
res = [x ^ y for (x, y) in zip(bits, enc_res[:nbits])]
bits_encrypt.extend(res)
qbits = qbits[nbits:] + enc_res[:nbits]
else:
bits = fullbits[(i * nbits):((i + 1) * nbits)]
enc_res = pea.encrypt(qbits, False)
res = [x ^ y for (x, y) in zip(bits, enc_res[:nbits])]
bits_encrypt.extend(res)
qbits = qbits[nbits:] + enc_res[:nbits]
return bits_to_text(bits_encrypt)
def ECB(text, key, decrypt=False):
fullbits = text_to_bits(text)
pea = PEA(key)
bits_encrypt = []
for i in range(int(len(fullbits) / 256)):
bits = fullbits[(i * 256):((i + 1) * 256)]
bits_encrypt.extend(pea.encrypt(bits, decrypt))
return bits_to_text(bits_encrypt)
def CBC(text, key, init_vector, decrypt=False):
fullbits = text_to_bits(text)
pea = PEA(key)
last_bits = init_vector
bits_encrypt = []
for i in range(int(len(fullbits) / 256)):
if not decrypt:
bits = fullbits[(i * 256):((i + 1) * 256)]
bits = [x ^ y for (x, y) in zip(bits, last_bits)]
res = pea.encrypt(bits, decrypt)
last_bits = res
bits_encrypt.extend(res)
else:
bits = fullbits[(i * 256):((i + 1) * 256)]
res = pea.encrypt(bits, decrypt)
res = [x ^ y for (x, y) in zip(res, last_bits)]
last_bits = bits
bits_encrypt.extend(res)
return bits_to_text(bits_encrypt)
def CTR(text, key, decrypt=False):
fullbits = text_to_bits(text)
pea = PEA(key)
bits_encrypt = []
count = create_ctr_start(key)
for i in range(int(len(fullbits) / 256)):
if not decrypt:
bits = fullbits[(i * 256):((i + 1) * 256)]
cbits = int_to_bits(count)
enc_res = pea.encrypt(cbits, False)
res = [x ^ y for (x, y) in zip(bits, enc_res)]
bits_encrypt.extend(res)
else:
bits = fullbits[(i * 256):((i + 1) * 256)]
cbits = int_to_bits(count)
enc_res = pea.encrypt(cbits, False)
res = [x ^ y for (x, y) in zip(bits, enc_res)]
bits_encrypt.extend(res)
count += 1
return bits_to_text(bits_encrypt)