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# ------------------------------------------------------------------------------
#
# R A B B I T Stream Cipher
# by M. Boesgaard, M. Vesterager, E. Zenner (specified in RFC 4503)
#
#
# Pure Python Implementation by Toni Mattis
#
# ------------------------------------------------------------------------------
WORDSIZE = 0x100000000
rot08 = lambda x: ((x << 8) & 0xFFFFFFFF) | (x >> 24)
rot16 = lambda x: ((x << 16) & 0xFFFFFFFF) | (x >> 16)
def _nsf(u, v):
'''Internal non-linear state transition'''
s = (u + v) % WORDSIZE
s = s * s
return (s ^ (s >> 32)) % WORDSIZE
class Rabbit:
def __init__(self, key, iv = None):
'''Initialize Rabbit cipher using a 128 bit integer/string'''
if isinstance(key, str):
# interpret key string in big endian byte order
if len(key) < 16:
key = '\x00' * (16 - len(key)) + key
# if len(key) > 16 bytes only the first 16 will be considered
k = [ord(key[i + 1]) | (ord(key[i]) << 8)
for i in xrange(14, -1, -2)]
else:
# k[0] = least significant 16 bits
# k[7] = most significant 16 bits
k = [(key >> i) & 0xFFFF for i in xrange(0, 128, 16)]
# State and counter initialization
x = [(k[(j + 5) % 8] << 16) | k[(j + 4) % 8] if j & 1 else
(k[(j + 1) % 8] << 16) | k[j] for j in xrange(8)]
c = [(k[j] << 16) | k[(j + 1) % 8] if j & 1 else
(k[(j + 4) % 8] << 16) | k[(j + 5) % 8] for j in xrange(8)]
self.x = x
self.c = c
self.b = 0
self._buf = 0 # output buffer
self._buf_bytes = 0 # fill level of buffer
self.next()
self.next()
self.next()
self.next()
for j in xrange(8):
c[j] ^= x[(j + 4) % 8]
self.start_x = self.x[:] # backup initial key for IV/reset
self.start_c = self.c[:]
self.start_b = self.b
if iv != None:
self.set_iv(iv)
def reset(self, iv = None):
'''Reset the cipher and optionally set a new IV (int64 / string).'''
self.c = self.start_c[:]
self.x = self.start_x[:]
self.b = self.start_b
self._buf = 0
self._buf_bytes = 0
if iv != None:
self.set_iv(iv)
def set_iv(self, iv):
'''Set a new IV (64 bit integer / bytestring).'''
if isinstance(iv, str):
i = 0
for c in iv:
i = (i << 8) | ord(c)
iv = i
c = self.c
i0 = iv & 0xFFFFFFFF
i2 = iv >> 32
i1 = ((i0 >> 16) | (i2 & 0xFFFF0000)) % WORDSIZE
i3 = ((i2 << 16) | (i0 & 0x0000FFFF)) % WORDSIZE
c[0] ^= i0
c[1] ^= i1
c[2] ^= i2
c[3] ^= i3
c[4] ^= i0
c[5] ^= i1
c[6] ^= i2
c[7] ^= i3
self.next()
self.next()
self.next()
self.next()
def next(self):
'''Proceed to the next internal state'''
c = self.c
x = self.x
b = self.b
t = c[0] + 0x4D34D34D + b
c[0] = t % WORDSIZE
t = c[1] + 0xD34D34D3 + t // WORDSIZE
c[1] = t % WORDSIZE
t = c[2] + 0x34D34D34 + t // WORDSIZE
c[2] = t % WORDSIZE
t = c[3] + 0x4D34D34D + t // WORDSIZE
c[3] = t % WORDSIZE
t = c[4] + 0xD34D34D3 + t // WORDSIZE
c[4] = t % WORDSIZE
t = c[5] + 0x34D34D34 + t // WORDSIZE
c[5] = t % WORDSIZE
t = c[6] + 0x4D34D34D + t // WORDSIZE
c[6] = t % WORDSIZE
t = c[7] + 0xD34D34D3 + t // WORDSIZE
c[7] = t % WORDSIZE
b = t // WORDSIZE
g = [_nsf(x[j], c[j]) for j in xrange(8)]
x[0] = (g[0] + rot16(g[7]) + rot16(g[6])) % WORDSIZE
x[1] = (g[1] + rot08(g[0]) + g[7]) % WORDSIZE
x[2] = (g[2] + rot16(g[1]) + rot16(g[0])) % WORDSIZE
x[3] = (g[3] + rot08(g[2]) + g[1]) % WORDSIZE
x[4] = (g[4] + rot16(g[3]) + rot16(g[2])) % WORDSIZE
x[5] = (g[5] + rot08(g[4]) + g[3]) % WORDSIZE
x[6] = (g[6] + rot16(g[5]) + rot16(g[4])) % WORDSIZE
x[7] = (g[7] + rot08(g[6]) + g[5]) % WORDSIZE
self.b = b
return self
def derive(self):
'''Derive a 128 bit integer from the internal state'''
x = self.x
return ((x[0] & 0xFFFF) ^ (x[5] >> 16)) | \
(((x[0] >> 16) ^ (x[3] & 0xFFFF)) << 16)| \
(((x[2] & 0xFFFF) ^ (x[7] >> 16)) << 32)| \
(((x[2] >> 16) ^ (x[5] & 0xFFFF)) << 48)| \
(((x[4] & 0xFFFF) ^ (x[1] >> 16)) << 64)| \
(((x[4] >> 16) ^ (x[7] & 0xFFFF)) << 80)| \
(((x[6] & 0xFFFF) ^ (x[3] >> 16)) << 96)| \
(((x[6] >> 16) ^ (x[1] & 0xFFFF)) << 112)
def keystream(self, n):
'''Generate a keystream of n bytes'''
res = ""
b = self._buf
j = self._buf_bytes
next = self.next
derive = self.derive
for i in xrange(n):
if not j:
j = 16
next()
b = derive()
res += chr(b & 0xFF)
j -= 1
b >>= 1
self._buf = b
self._buf_bytes = j
return res
def encrypt(self, data):
'''Encrypt/Decrypt data of arbitrary length.'''
res = ""
b = self._buf
j = self._buf_bytes
next = self.next
derive = self.derive
for c in data:
if not j: # empty buffer => fetch next 128 bits
j = 16
next()
b = derive()
res += chr(ord(c) ^ (b & 0xFF))
j -= 1
b >>= 1
self._buf = b
self._buf_bytes = j
return res
decrypt = encrypt
if __name__ == "__main__":
import time
# --- Official Test Vectors ---
# RFC 4503 Appendix A.1 - Testing without IV Setup
r = Rabbit(0)
assert r.next().derive() == 0xB15754F036A5D6ECF56B45261C4AF702
assert r.next().derive() == 0x88E8D815C59C0C397B696C4789C68AA7
assert r.next().derive() == 0xF416A1C3700CD451DA68D1881673D696
r = Rabbit(0x912813292E3D36FE3BFC62F1DC51C3AC)
assert r.next().derive() == 0x3D2DF3C83EF627A1E97FC38487E2519C
assert r.next().derive() == 0xF576CD61F4405B8896BF53AA8554FC19
assert r.next().derive() == 0xE5547473FBDB43508AE53B20204D4C5E
r = Rabbit(0x8395741587E0C733E9E9AB01C09B0043)
assert r.next().derive() == 0x0CB10DCDA041CDAC32EB5CFD02D0609B
assert r.next().derive() == 0x95FC9FCA0F17015A7B7092114CFF3EAD
assert r.next().derive() == 0x9649E5DE8BFC7F3F924147AD3A947428
# RFC 4503 Appendix A.2 - Testing with IV Setup
r = Rabbit(0, 0)
assert r.next().derive() == 0xC6A7275EF85495D87CCD5D376705B7ED
assert r.next().derive() == 0x5F29A6AC04F5EFD47B8F293270DC4A8D
assert r.next().derive() == 0x2ADE822B29DE6C1EE52BDB8A47BF8F66
r = Rabbit(0, 0xC373F575C1267E59)
assert r.next().derive() == 0x1FCD4EB9580012E2E0DCCC9222017D6D
assert r.next().derive() == 0xA75F4E10D12125017B2499FFED936F2E
assert r.next().derive() == 0xEBC112C393E738392356BDD012029BA7
r = Rabbit(0, 0xA6EB561AD2F41727)
assert r.next().derive() == 0x445AD8C805858DBF70B6AF23A151104D
assert r.next().derive() == 0x96C8F27947F42C5BAEAE67C6ACC35B03
assert r.next().derive() == 0x9FCBFC895FA71C17313DF034F01551CB
# --- Performance Tests ---
def test_gen(n = 1048576):
'''Measure time for generating n bytes => (total, bytes per second)'''
r = Rabbit(0)
t = time.time()
r.keystream(n)
t = time.time() - t
return t, n / t
def test_enc(n = 1048576):
'''Measure time for encrypting n bytes => (total, bytes per second)'''
r = Rabbit(0)
x = 'x' * n
t = time.time()
r.encrypt(x)
t = time.time() - t
return t, n / t
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