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class SpeckEncrypt():
def __init__(self, key):
# Perform key expansion and store the round keys
self.key = key & ((2 ** 128) - 1)
self.key_schedule = [self.key & 0xFFFFFFFF]
key_buf = [(self.key >> (x * 32)) & 0xFFFFFFFF for x in range(1, 4)]
for x in range(26):
k = self.encryption_round(key_buf[x], self.key_schedule[x], x)
key_buf.append(k[0])
self.key_schedule.append(k[1])
def encryption_round(self, x, y, k):
# Perform one encryption round of the speck cipher
x_shift = ((x << 24) + (x >> 8)) & 0xFFFFFFFF
x_enc = k ^ ((x_shift + y) & 0xFFFFFFFF)
y_shift = ((y >> 29) + (y << 3)) & 0xFFFFFFFF
y_enc = x_enc ^ y_shift
return x_enc, y_enc
def decryption_round(self, x, y, k):
# Perform one decryption round of the speck cipher
new_y = (((x ^ y) << 29) + ((x ^ y) >> 3)) & 0xFFFFFFFF
msub = (((x ^ k) - new_y) + 0x100000000) % 0x100000000
new_x = ((msub >> 24) + (msub << 8)) & 0xFFFFFFFF
return new_x, new_y
def encrypt_block(self, plain):
# Encrypt one 64 bit block
x = (plain >> 32) & 0xFFFFFFFF
y = plain & 0xFFFFFFFF
for k in self.key_schedule:
x, y = self.encryption_round(x, y, k)
encrypted = (x << 32) + y
return encrypted
def decrypt_block(self, encrypted):
# Decrypt one 64 bit block
x = (encrypted >> 32) & 0xFFFFFFFF
y = encrypted & 0xFFFFFFFF
for k in reversed(self.key_schedule):
x, y = self.decryption_round(x, y, k)
plain = (x << 32) + y
return plain
def encrypt(self, iv, plain):
plain = bytearray(plain)
input_length = len(plain)
plain.extend(bytes(b'\x00' * (8 - (input_length % 8))))
iv = int.from_bytes(iv.to_bytes(8, byteorder='big'), byteorder='little', signed=False)
output = bytearray()
for i in range(len(plain) // 8):
k = self.encrypt_block(iv)
res = k ^ int.from_bytes(plain[i*8:i*8+8], byteorder='little', signed=False)
output.extend(int.to_bytes(res, 8, byteorder='little', signed=False))
iv += 1
encrypted = output[:input_length]
return bytes(encrypted)
def decrypt(self, iv, encrypted):
return self.encrypt(iv, encrypted)
class SpeckCMAC:
def __init__(self, key):
self.cipher = SpeckEncrypt(key)
k0 = self.cipher.encrypt_block(0)
k0 = int.from_bytes(k0.to_bytes(8, byteorder='big'), byteorder='little', signed=False)
k1 = (k0 << 1) & 0XFFFFFFFFFFFFFFFF
if (k0 >> 63 != 0):
k1 ^= 0x1B
k2 = (k1 << 1) & 0XFFFFFFFFFFFFFFFF
if (k1 >> 63 != 0):
k2 ^= 0x1B
k1 = int.from_bytes(k1.to_bytes(8, byteorder='big'), byteorder='little', signed=False)
k2 = int.from_bytes(k2.to_bytes(8, byteorder='big'), byteorder='little', signed=False)
self.k1 = k1
self.k2 = k2
def sign(self, data):
c = 0
i = 0
data_len = len(data)
while (i < data_len):
data_left = data_len - i
if (data_left == 8):
block = int.from_bytes(data[i:i+8], 'little') ^ self.k1
elif (data_left < 8):
block = int.from_bytes(data[i:i+data_left] + b'\x80' + b'\x00'*(7-data_left), 'little') ^ self.k2
else:
block = int.from_bytes(data[i:i+8], 'little')
c = self.cipher.encrypt_block(c ^ block)
i += 8
return c
def derive(self, label, context):
data = label + b'\x00' + context + b'\x80\x00'
d1 = self.sign(b'\x01' + data)
d2 = self.sign(b'\x02' + data) << 64
return d1 | d2
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