def bmix(self, source, target):
"""
block mixing function used by smix()
uses salsa20/8 core to mix block contents.
:arg source:
source to read from.
should be list of 32*r 4-byte integers
(2*r salsa20 blocks).
:arg target:
target to write to.
should be list with same size as source.
the existing value of this buffer is ignored.
.. warning::
this operates *in place* on target,
so source & target should NOT be same list.
.. note::
* time cost is ``O(r)`` -- loops 16*r times, salsa20() has ``O(1)`` cost.
* memory cost is ``O(1)`` -- salsa20() uses 16 x uint4,
all other operations done in-place.
"""
## assert source is not target
# Y[-1] = B[2r-1], Y[i] = hash( Y[i-1] xor B[i])
# B' <-- (Y_0, Y_2 ... Y_{2r-2}, Y_1, Y_3 ... Y_{2r-1}) */
half = self.bmix_half_len # 16*r out of 32*r - start of Y_1
tmp = source[-16:] # 'X' in scrypt source
siter = iter(source)
j = 0
while j < half:
jn = j + 16
target[j:jn] = tmp = salsa20(a ^ b for a, b in izip(tmp, siter))
target[half + j:half + jn] = tmp = salsa20(
a ^ b for a, b in izip(tmp, siter))
j = jn
def _bmix_1(self, source, target):
"""special bmix() method optimized for ``r=1`` case"""
B = source[16:]
target[:16] = tmp = salsa20(a ^ b for a, b in izip(B, iter(source)))
target[16:] = salsa20(a ^ b for a, b in izip(tmp, B))