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boolean_function.pyx
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boolean_function.pyx
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# -*- coding: utf-8 -*-
"""
Boolean functions
Those functions are used for example in LFSR based ciphers like
the filter generator or the combination generator.
This module allows to study properties linked to spectral analysis,
and also algebraic immunity.
EXAMPLES::
sage: R.<x>=GF(2^8,'a')[]
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction( x^254 ) # the Boolean function Tr(x^254)
sage: B
Boolean function with 8 variables
sage: B.nonlinearity()
112
sage: B.algebraic_immunity()
4
AUTHOR:
- Rusydi H. Makarim (2016-10-13): add functions related to linear structures
- Rusydi H. Makarim (2016-07-09): add is_plateaued()
- Yann Laigle-Chapuy (2010-02-26): add basic arithmetic
- Yann Laigle-Chapuy (2009-08-28): first implementation
"""
from cysignals.signals cimport sig_check
from libc.string cimport memcpy
from sage.structure.sage_object cimport SageObject
from sage.structure.richcmp cimport rich_to_bool
from sage.rings.integer_ring import ZZ
from sage.rings.integer cimport Integer
from sage.rings.finite_rings.finite_field_constructor import GF
from sage.rings.polynomial.pbori import BooleanPolynomial
from sage.rings.finite_rings.finite_field_constructor import is_FiniteField
from sage.rings.finite_rings.finite_field_givaro import FiniteField_givaro
from sage.rings.polynomial.polynomial_element import is_Polynomial
from sage.misc.superseded import deprecated_function_alias
include "sage/data_structures/bitset.pxi"
# for details about the implementation of hamming_weight_int,
# walsh_hadamard transform, reed_muller transform, and a lot
# more, see 'Matters computational' available on www.jjj.de.
cdef inline unsigned int hamming_weight_int(unsigned int x):
# valid for 32bits
x -= (x>>1) & 0x55555555UL # 0-2 in 2 bits
x = ((x>>2) & 0x33333333UL) + (x & 0x33333333UL) # 0-4 in 4 bits
x = ((x>>4) + x) & 0x0f0f0f0fUL # 0-8 in 8 bits
x *= 0x01010101UL
return x>>24
cdef walsh_hadamard(long *f, int ldn):
r"""
The Walsh Hadamard transform is an orthogonal transform equivalent
to a multidimensional discrete Fourier transform of size 2x2x...x2.
It can be defined by the following formula:
.. MATH:: W(j) = \sum_{i\in\{0,1\}^n} (-1)^{f(i)\oplus i \cdot j}
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction([1,0,0,1])
sage: B.walsh_hadamard_transform() # indirect doctest
(0, 0, 0, -4)
"""
cdef long n, ldm, m, mh, t1, t2, r
n = 1 << ldn
for 1 <= ldm <= ldn:
m = (1<<ldm)
mh = m//2
for 0 <= r <n by m:
t1 = r
t2 = r+mh
for 0 <= j < mh:
sig_check()
u = f[t1]
v = f[t2]
f[t1] = u + v
f[t2] = u - v
t1 += 1
t2 += 1
cdef long yellow_code(unsigned long a):
"""
The yellow-code is just a Reed Muller transform applied to a
word.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: R.<x,y,z> = BooleanPolynomialRing(3)
sage: P = x*y
sage: B = BooleanFunction( P )
sage: B.truth_table() # indirect doctest
(False, False, False, True, False, False, False, True)
"""
cdef unsigned long s = (8*sizeof(unsigned long))>>1
cdef unsigned long m = (~0UL) >> s
cdef unsigned long r = a
while(s):
sig_check()
r ^= ( (r&m) << s )
s >>= 1
m ^= (m<<s)
return r
cdef reed_muller(mp_limb_t* f, int ldn):
r"""
The Reed Muller transform (also known as binary Möbius transform)
is an orthogonal transform. For a function `f` defined by
.. MATH:: f(x) = \bigoplus_{I\subset\{1,\ldots,n\}} \left(a_I \prod_{i\in I} x_i\right)
it allows to compute efficiently the ANF from the truth table and
vice versa, using the formulae:
.. MATH:: f(x) = \bigoplus_{support(x)\subset I} a_I
.. MATH:: a_i = \bigoplus_{I\subset support(x)} f(x)
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: R.<x,y,z> = BooleanPolynomialRing(3)
sage: P = x*y
sage: B = BooleanFunction( P )
sage: B.truth_table() # indirect doctest
(False, False, False, True, False, False, False, True)
"""
cdef long n, ldm, m, mh, t1, t2, r
n = 1 << ldn
# intra word transform
for 0 <= r < n:
f[r] = yellow_code(f[r])
# inter word transform
for 1 <= ldm <= ldn:
m = (1<<ldm)
mh = m//2
for 0 <= r <n by m:
t1 = r
t2 = r+mh
for 0 <= j < mh:
sig_check()
f[t2] ^= f[t1]
t1 += 1
t2 += 1
cdef class BooleanFunction(SageObject):
r"""
This module implements Boolean functions represented as a truth table.
We can construct a Boolean Function from either:
- an integer - the result is the zero function with ``x`` variables;
- a list - it is expected to be the truth table of the
result. Therefore it must be of length a power of 2, and its
elements are interpreted as Booleans;
- a string - representing the truth table in hexadecimal;
- a Boolean polynomial - the result is the corresponding Boolean function;
- a polynomial P over an extension of GF(2) - the result is
the Boolean function with truth table ``( Tr(P(x)) for x in
GF(2^k) )``
EXAMPLES:
from the number of variables::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: BooleanFunction(5)
Boolean function with 5 variables
from a truth table::
sage: BooleanFunction([1,0,0,1])
Boolean function with 2 variables
note that elements can be of different types::
sage: B = BooleanFunction([False, sqrt(2)])
sage: B
Boolean function with 1 variable
sage: [b for b in B]
[False, True]
from a string::
sage: BooleanFunction("111e")
Boolean function with 4 variables
from a :class:`sage.rings.polynomial.pbori.BooleanPolynomial`::
sage: R.<x,y,z> = BooleanPolynomialRing(3)
sage: P = x*y
sage: BooleanFunction( P )
Boolean function with 3 variables
from a polynomial over a binary field::
sage: R.<x> = GF(2^8,'a')[]
sage: B = BooleanFunction( x^7 )
sage: B
Boolean function with 8 variables
two failure cases::
sage: BooleanFunction(sqrt(2))
Traceback (most recent call last):
...
TypeError: unable to init the Boolean function
sage: BooleanFunction([1, 0, 1])
Traceback (most recent call last):
...
ValueError: the length of the truth table must be a power of 2
"""
cdef bitset_t _truth_table
cdef object _walsh_hadamard_transform
cdef object _nvariables
cdef object _nonlinearity
cdef object _correlation_immunity
cdef object _autocorrelation
cdef object _absolute_indicator
cdef object _sum_of_square_indicator
def __cinit__(self, x):
r"""
Construct a Boolean Function.
The input ``x`` can be either:
- an integer - the result is the zero function with ``x`` variables;
- a list - it is expected to be the truth table of the
result. Therefore it must be of length a power of 2, and its
elements are interpreted as Booleans;
- a Boolean polynomial - the result is the corresponding Boolean function;
- a polynomial P over an extension of GF(2) - the result is
the Boolean function with truth table ``( Tr(P(x)) for x in
GF(2^k) )``
EXAMPLES:
from the number of variables::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: BooleanFunction(5)
Boolean function with 5 variables
from a truth table::
sage: BooleanFunction([1,0,0,1])
Boolean function with 2 variables
note that elements can be of different types::
sage: B = BooleanFunction([False, sqrt(2)])
sage: B
Boolean function with 1 variable
sage: [b for b in B]
[False, True]
from a :class:`sage.rings.polynomial.pbori.BooleanPolynomial`::
sage: R.<x,y,z> = BooleanPolynomialRing(3)
sage: P = x*y
sage: BooleanFunction( P )
Boolean function with 3 variables
from a polynomial over a binary field::
sage: R.<x> = GF(2^8,'a')[]
sage: B = BooleanFunction( x^7 )
sage: B
Boolean function with 8 variables
two failure cases::
sage: BooleanFunction(sqrt(2))
Traceback (most recent call last):
...
TypeError: unable to init the Boolean function
sage: BooleanFunction([1, 0, 1])
Traceback (most recent call last):
...
ValueError: the length of the truth table must be a power of 2
"""
if isinstance(x, str):
L = ZZ(len(x))
if L.is_power_of(2):
x = ZZ("0x"+x).digits(base=2,padto=4*L)
else:
raise ValueError("the length of the truth table must be a power of 2")
from types import GeneratorType
if isinstance(x, (list,tuple,GeneratorType)):
# initialisation from a truth table
# first, check the length
L = ZZ(len(x))
if L.is_power_of(2):
self._nvariables = L.exact_log(2)
else:
raise ValueError("the length of the truth table must be a power of 2")
# then, initialize our bitset
bitset_init(self._truth_table, L)
for 0<= i < L:
bitset_set_to(self._truth_table, i, x[i])#int(x[i])&1)
elif isinstance(x, BooleanPolynomial):
# initialisation from a Boolean polynomial
self._nvariables = ZZ(x.parent().ngens())
bitset_init(self._truth_table, (1<<self._nvariables))
bitset_zero(self._truth_table)
for m in x:
i = sum( [1<<k for k in m.iterindex()] )
bitset_set(self._truth_table, i)
reed_muller(self._truth_table.bits, ZZ(self._truth_table.limbs).exact_log(2) )
elif isinstance(x, (int,long,Integer) ):
# initialisation to the zero function
self._nvariables = ZZ(x)
bitset_init(self._truth_table,(1<<self._nvariables))
bitset_zero(self._truth_table)
elif is_Polynomial(x):
K = x.base_ring()
if is_FiniteField(K) and K.characteristic() == 2:
self._nvariables = K.degree()
bitset_init(self._truth_table,(1<<self._nvariables))
bitset_zero(self._truth_table)
if isinstance(K,FiniteField_givaro): #the ordering is not the same in this case
for u in K:
bitset_set_to(self._truth_table, ZZ(u._vector_().list(),2) , (x(u)).trace())
else:
for i,u in enumerate(K):
bitset_set_to(self._truth_table, i , (x(u)).trace())
elif isinstance(x, BooleanFunction):
self._nvariables = x.nvariables()
bitset_init(self._truth_table,(1<<self._nvariables))
bitset_copy(self._truth_table,(<BooleanFunction>x)._truth_table)
else:
raise TypeError("unable to init the Boolean function")
def __dealloc__(self):
bitset_free(self._truth_table)
def _repr_(self):
"""
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: BooleanFunction(4) #indirect doctest
Boolean function with 4 variables
"""
r = "Boolean function with " + self._nvariables.str() + " variable"
if self._nvariables>1:
r += "s"
return r
def __invert__(self):
"""
Return the complement Boolean function of `self`.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B=BooleanFunction([0, 1, 1, 0, 1, 0, 0, 0])
sage: (~B).truth_table(format='int')
(1, 0, 0, 1, 0, 1, 1, 1)
"""
cdef BooleanFunction res=BooleanFunction(self.nvariables())
bitset_complement(res._truth_table, self._truth_table)
return res
def __add__(self, BooleanFunction other):
"""
Return the element wise sum of `self`and `other` which must have the same number of variables.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: A=BooleanFunction([0, 1, 0, 1, 1, 0, 0, 1])
sage: B=BooleanFunction([0, 1, 1, 0, 1, 0, 0, 0])
sage: (A+B).truth_table(format='int')
(0, 0, 1, 1, 0, 0, 0, 1)
it also corresponds to the addition of algebraic normal forms::
sage: S = A.algebraic_normal_form() + B.algebraic_normal_form()
sage: (A+B).algebraic_normal_form() == S
True
TESTS::
sage: A+BooleanFunction([0,1])
Traceback (most recent call last):
...
ValueError: the two Boolean functions must have the same number of variables
"""
if (self.nvariables() != other.nvariables() ):
raise ValueError("the two Boolean functions must have the same number of variables")
cdef BooleanFunction res = BooleanFunction(self)
bitset_xor(res._truth_table, res._truth_table, other._truth_table)
return res
def __mul__(self, BooleanFunction other):
"""
Return the elementwise multiplication of `self`and `other` which must have the same number of variables.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: A=BooleanFunction([0, 1, 0, 1, 1, 0, 0, 1])
sage: B=BooleanFunction([0, 1, 1, 0, 1, 0, 0, 0])
sage: (A*B).truth_table(format='int')
(0, 1, 0, 0, 1, 0, 0, 0)
it also corresponds to the multiplication of algebraic normal forms::
sage: P = A.algebraic_normal_form() * B.algebraic_normal_form()
sage: (A*B).algebraic_normal_form() == P
True
TESTS::
sage: A*BooleanFunction([0,1])
Traceback (most recent call last):
...
ValueError: the two Boolean functions must have the same number of variables
"""
if (self.nvariables() != other.nvariables() ):
raise ValueError("the two Boolean functions must have the same number of variables")
cdef BooleanFunction res = BooleanFunction(self)
bitset_and(res._truth_table, res._truth_table, other._truth_table)
return res
def __or__(BooleanFunction self, BooleanFunction other):
"""
Return the concatenation of `self` and `other` which must have the same number of variables.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: A=BooleanFunction([0, 1, 0, 1])
sage: B=BooleanFunction([0, 1, 1, 0])
sage: (A|B).truth_table(format='int')
(0, 1, 0, 1, 0, 1, 1, 0)
sage: C = A.truth_table() + B.truth_table()
sage: (A|B).truth_table(format='int') == C
True
TESTS::
sage: A|BooleanFunction([0,1])
Traceback (most recent call last):
...
ValueError: the two Boolean functions must have the same number of variables
"""
if (self._nvariables != other.nvariables()):
raise ValueError("the two Boolean functions must have the same number of variables")
cdef BooleanFunction res=BooleanFunction(self.nvariables()+1)
nb_limbs = self._truth_table.limbs
if nb_limbs == 1:
L = len(self)
for i in xrange(L):
res[i ]=self[i]
res[i+L]=other[i]
return res
memcpy(res._truth_table.bits , self._truth_table.bits, nb_limbs * sizeof(unsigned long))
memcpy(&(res._truth_table.bits[nb_limbs]),other._truth_table.bits, nb_limbs * sizeof(unsigned long))
return res
def algebraic_normal_form(self):
"""
Return the :class:`sage.rings.polynomial.pbori.BooleanPolynomial`
corresponding to the algebraic normal form.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction([0,1,1,0,1,0,1,1])
sage: P = B.algebraic_normal_form()
sage: P
x0*x1*x2 + x0 + x1*x2 + x1 + x2
sage: [ P(*ZZ(i).digits(base=2,padto=3)) for i in range(8) ]
[0, 1, 1, 0, 1, 0, 1, 1]
"""
cdef bitset_t anf
bitset_init(anf, (1<<self._nvariables))
bitset_copy(anf, self._truth_table)
reed_muller(anf.bits, ZZ(anf.limbs).exact_log(2))
from sage.rings.polynomial.pbori import BooleanPolynomialRing
R = BooleanPolynomialRing(self._nvariables,"x")
G = R.gens()
P = R(0)
for 0 <= i < anf.limbs:
if anf.bits[i]:
inf = i*sizeof(long)*8
sup = min( (i+1)*sizeof(long)*8 , (1<<self._nvariables) )
for inf <= j < sup:
if bitset_in(anf,j):
m = R(1)
for 0 <= k < self._nvariables:
if (j>>k)&1:
m *= G[k]
P+=m
bitset_free(anf)
return P
def nvariables(self):
"""
The number of variables of this function.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: BooleanFunction(4).nvariables()
4
"""
return self._nvariables
def truth_table(self,format='bin'):
"""
The truth table of the Boolean function.
INPUT: a string representing the desired format, can be either
- 'bin' (default) : we return a tuple of Boolean values
- 'int' : we return a tuple of 0 or 1 values
- 'hex' : we return a string representing the truth_table in hexadecimal
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: R.<x,y,z> = BooleanPolynomialRing(3)
sage: B = BooleanFunction( x*y*z + z + y + 1 )
sage: B.truth_table()
(True, True, False, False, False, False, True, False)
sage: B.truth_table(format='int')
(1, 1, 0, 0, 0, 0, 1, 0)
sage: B.truth_table(format='hex')
'43'
sage: BooleanFunction('00ab').truth_table(format='hex')
'00ab'
sage: H = '0abbacadabbacad0'
sage: len(H)
16
sage: T = BooleanFunction(H).truth_table(format='hex')
sage: T == H
True
sage: H = H * 4
sage: T = BooleanFunction(H).truth_table(format='hex')
sage: T == H
True
sage: H = H * 4
sage: T = BooleanFunction(H).truth_table(format='hex')
sage: T == H
True
sage: len(T)
256
sage: B.truth_table(format='oct')
Traceback (most recent call last):
...
ValueError: unknown output format
"""
if format == 'bin':
return tuple(self)
if format == 'int':
return tuple(map(int,self))
if format == 'hex':
S = ZZ(self.truth_table(),2).str(16)
S = "0"*((1<<(self._nvariables-2)) - len(S)) + S
return S
raise ValueError("unknown output format")
def __len__(self):
"""
Return the number of different input values.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: len(BooleanFunction(4))
16
"""
return 2**self._nvariables
def __richcmp__(BooleanFunction self, other, int op):
"""
Boolean functions are considered to be equal if the number of
input variables is the same, and all the values are equal.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: b1 = BooleanFunction([0,1,1,0])
sage: b2 = BooleanFunction([0,1,1,0])
sage: b3 = BooleanFunction([0,1,1,1])
sage: b4 = BooleanFunction([0,1])
sage: b1 == b2
True
sage: b1 == b3
False
sage: b1 == b4
False
"""
if not isinstance(other, BooleanFunction):
return NotImplemented
o = <BooleanFunction>other
return rich_to_bool(op, bitset_cmp(self._truth_table, o._truth_table))
def __call__(self, x):
"""
Return the value of the function for the given input.
INPUT: either
- a list - then all elements are evaluated as Booleans
- an integer - then we consider its binary representation
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction([0,1,0,0])
sage: B(1)
1
sage: B([1,0])
1
sage: B(4)
Traceback (most recent call last):
...
IndexError: index out of bound
"""
if isinstance(x, (int,long,Integer)):
if x >= self._truth_table.size:
raise IndexError("index out of bound")
return bitset_in(self._truth_table,x)
elif isinstance(x, list):
if len(x) != self._nvariables:
raise ValueError("bad number of inputs")
return self(ZZ([bool(_) for _ in x], 2))
else:
raise TypeError("cannot apply Boolean function to provided element")
def __iter__(self):
"""
Iterate through the value of the function.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction([0,1,1,0,1,0,1,0])
sage: [int(b) for b in B]
[0, 1, 1, 0, 1, 0, 1, 0]
"""
return BooleanFunctionIterator(self)
def _walsh_hadamard_transform_cached(self):
"""
Return the cached Walsh Hadamard transform. *Unsafe*, no check.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction(3)
sage: W = B.walsh_hadamard_transform()
sage: B._walsh_hadamard_transform_cached() is W
True
"""
return self._walsh_hadamard_transform
def walsh_hadamard_transform(self):
r"""
Compute the Walsh Hadamard transform `W` of the function `f`.
.. MATH:: W(j) = \sum_{i\in\{0,1\}^n} (-1)^{f(i)\oplus i \cdot j}
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: R.<x> = GF(2^3,'a')[]
sage: B = BooleanFunction( x^3 )
sage: B.walsh_hadamard_transform()
(0, -4, 0, 4, 0, 4, 0, 4)
"""
cdef long *temp
if self._walsh_hadamard_transform is None:
n = self._truth_table.size
temp = <long *>sig_malloc(sizeof(long)*n)
for 0<= i < n:
temp[i] = 1 - (bitset_in(self._truth_table,i)<<1)
walsh_hadamard(temp, self._nvariables)
self._walsh_hadamard_transform = tuple(temp[i] for i in xrange(n))
sig_free(temp)
return self._walsh_hadamard_transform
def absolute_walsh_spectrum(self):
"""
Return the absolute Walsh spectrum fo the function.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction("7969817CC5893BA6AC326E47619F5AD0")
sage: sorted(B.absolute_walsh_spectrum().items())
[(0, 64), (16, 64)]
sage: B = BooleanFunction("0113077C165E76A8")
sage: B.absolute_walsh_spectrum()
{8: 64}
"""
d = {}
for i in self.walsh_hadamard_transform():
if abs(i) in d:
d[abs(i)] += 1
else:
d[abs(i)] = 1
return d
def is_balanced(self):
"""
Return True if the function takes the value True half of the time.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction(1)
sage: B.is_balanced()
False
sage: B[0] = True
sage: B.is_balanced()
True
"""
return self.walsh_hadamard_transform()[0] == 0
def is_symmetric(self):
"""
Return True if the function is symmetric, i.e. invariant under
permutation of its input bits. Another way to see it is that the
output depends only on the Hamming weight of the input.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction(5)
sage: B[3] = 1
sage: B.is_symmetric()
False
sage: V_B = [0, 1, 1, 0, 1, 0]
sage: for i in srange(32): B[i] = V_B[i.popcount()]
sage: B.is_symmetric()
True
"""
cdef list T = [ self(2**i-1) for i in xrange(self._nvariables+1) ]
for i in xrange(2**self._nvariables):
sig_check()
if T[ hamming_weight_int(i) ] != bitset_in(self._truth_table, i):
return False
return True
def nonlinearity(self):
"""
Return the nonlinearity of the function. This is the distance
to the linear functions, or the number of output ones need to
change to obtain a linear function.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction(5)
sage: B[1] = B[3] = 1
sage: B.nonlinearity()
2
sage: B = BooleanFunction("0113077C165E76A8")
sage: B.nonlinearity()
28
"""
if self._nonlinearity is None:
self._nonlinearity = ( (1<<self._nvariables) - max( [abs(w) for w in self.walsh_hadamard_transform()] ) ) >> 1
return self._nonlinearity
def is_bent(self):
"""
Return True if the function is bent.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction("0113077C165E76A8")
sage: B.is_bent()
True
"""
if (self._nvariables & 1):
return False
return self.nonlinearity() == ((1<<self._nvariables)-(1<<(self._nvariables//2)))>>1
def correlation_immunity(self):
"""
Return the maximum value `m` such that the function is
correlation immune of order `m`.
A Boolean function is said to be correlation immune of order
`m` , if the output of the function is statistically
independent of the combination of any m of its inputs.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction("7969817CC5893BA6AC326E47619F5AD0")
sage: B.correlation_immunity()
2
"""
cdef size_t c
if self._correlation_immunity is None:
c = self._nvariables
W = self.walsh_hadamard_transform()
for 0 < i < len(W):
sig_check()
if W[i]:
c = min( c , hamming_weight_int(i) )
self._correlation_immunity = ZZ(c-1)
return self._correlation_immunity
def resiliency_order(self):
"""
Return the maximum value `m` such that the function is
resilient of order `m`.
A Boolean function is said to be resilient of order `m` if it
is balanced and correlation immune of order `m`.
If the function is not balanced, we return -1.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction("077CE5A2F8831A5DF8831A5D077CE5A26996699669699696669999665AA5A55A")
sage: B.resiliency_order()
3
"""
if not self.is_balanced():
return -1
return self.correlation_immunity()
def autocorrelation(self):
r"""
Return the autocorrelation of the function, defined by
.. MATH:: \Delta_f(j) = \sum_{i\in\{0,1\}^n} (-1)^{f(i)\oplus f(i\oplus j)}.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction("03")
sage: B.autocorrelation()
(8, 8, 0, 0, 0, 0, 0, 0)
"""
cdef long *temp
if self._autocorrelation is None:
n = self._truth_table.size
temp = <long *>sig_malloc(sizeof(long)*n)
W = self.walsh_hadamard_transform()
for 0 <= i < n:
sig_check()
temp[i] = W[i]*W[i]
walsh_hadamard(temp, self._nvariables)
self._autocorrelation = tuple(temp[i]>>self._nvariables for i in xrange(n))
sig_free(temp)
return self._autocorrelation
def absolute_autocorrelation(self):
"""
Return the absolute autocorrelation of the function.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction("7969817CC5893BA6AC326E47619F5AD0")
sage: sorted(B.absolute_autocorrelation().items())
[(0, 33), (8, 58), (16, 28), (24, 6), (32, 2), (128, 1)]
"""
d = {}
for i in self.autocorrelation():
if abs(i) in d:
d[abs(i)] += 1
else:
d[abs(i)] = 1
return d
def absolute_indicator(self):
"""
Return the absolute indicator of the function.
The absolute indicator is defined as the maximal absolute value of
the autocorrelation.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction("7969817CC5893BA6AC326E47619F5AD0")
sage: B.absolute_indicator()
32
The old method's name contained a typo, it is deprecated::
sage: B.absolut_indicator()
doctest:warning
...
DeprecationWarning: absolut_indicator is deprecated. Please use absolute_indicator instead.
See https://trac.sagemath.org/28001 for details.
32
"""
if self._absolute_indicator is None:
D = self.autocorrelation()
self._absolute_indicator = max([ abs(a) for a in D[1:] ])
return self._absolute_indicator
absolut_indicator = deprecated_function_alias(28001, absolute_indicator)
def sum_of_square_indicator(self):
"""
Return the sum of square indicator of the function.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: B = BooleanFunction("7969817CC5893BA6AC326E47619F5AD0")
sage: B.sum_of_square_indicator()
32768
"""
if self._sum_of_square_indicator is None:
D = self.autocorrelation()
self._sum_of_square_indicator = sum([ a**2 for a in D ])
return self._sum_of_square_indicator
def annihilator(self,d, dim = False):
r"""
Return (if it exists) an annihilator of the boolean function of
degree at most `d`, that is a Boolean polynomial `g` such that
.. MATH::
f(x)g(x) = 0 \forall x.
INPUT:
- ``d`` -- an integer;
- ``dim`` -- a Boolean (default: False), if True, return also
the dimension of the annihilator vector space.
EXAMPLES::
sage: from sage.crypto.boolean_function import BooleanFunction
sage: f = BooleanFunction("7969817CC5893BA6AC326E47619F5AD0")
sage: f.annihilator(1) is None
True
sage: g = BooleanFunction( f.annihilator(3) )
sage: set([ fi*g(i) for i,fi in enumerate(f) ])
{0}
"""
# NOTE: this is a toy implementation
from sage.rings.polynomial.polynomial_ring_constructor import BooleanPolynomialRing_constructor
R = BooleanPolynomialRing_constructor(self._nvariables,'x')
G = R.gens()
r = [R(1)]
from sage.modules.all import vector
s = vector(self.truth_table()).support()
from sage.combinat.combination import Combinations
from sage.misc.all import prod