Hint¶

Hint module¶

class fips.FIPS204.hint.HINT(parameter)[source]¶

Bases: object

contains power2round, highbits, lowbits, makehint and use hint.

Parameters:: parameter (dict[str, int])

Algorithm 35

Decomposes an integer r into (r1, r0) such that

r ≡ r1 * (2 * d) + r0 (mod q)

Parameters:: r (int) – An integer coefficient.
Returns:: A tuple containing the high bits r₁ and low bits r₀.
Return type:: tuple[int, int]

Power2RoundVector(t_vec)[source]¶

Algorithm 35 modified

Applies Power2Round component-wise to a vector of polynomials.

Parameters:: t_vec (list[list[int]]) – A vector of polynomials.
Returns:: Tuple(t₁, t₀) of two vectors of polynomials, where t₁ contains the high bits and t₀ contains the low bits.
Return type:: tuple[list[list[int]], list[list[int]]]
Raises:: TypeError – If the input is not a list or tuple, or if any polynomial or coefficient is not an integer.

Decompose(r)[source]¶

Algorithm 36

Decompose r into (r1, r0) such that:

r ≡ r1 * (2 * gamma2) + r0 (mod q)

Parameters:

r (int) – Integer in the range [0, q - 1].

Return type:

tuple[int, int]

Returns:

r1 The high bits.
r0 The low bits in the range [-2^(d-1)+1, 2^(d-1)].

Raises:

TypeError – If r is not an integer.

HighBits(r)[source]¶

Algorithm 37

Returns r1 from the output of Decompose(r).

Parameters:: r (int) – An integer in the range [0, q-1].
Returns:: The high bits r1.
Return type:: int
Raises:: TypeError – If r is not an integer.

LowBits(r)[source]¶

Algorithm 38

Returns r0 from the output of Decompose(r).

Parameters:: r (int) – An integer in the range [0, q-1].
Returns:: The low bits r0.
Return type:: int
Raises:: TypeError – If r is not an integer.

MakeHint(z, r)[source]¶

Algorithm 39

Computes hint bit indicating whether adding z to r alters the high bits of r.

Parameters:

z (int) – An integer in the range [0, q-1].
r (int) – An integer in the range [0, q-1].

Returns:

True if the high bits change, False otherwise.

Return type:

bool

Raises:

TypeError – If z or r is not an integer.

UseHint(h, r)[source]¶

Algorithm 40

Returns the high bits of r adjusted according to hint h.

Parameters:

h (bool) – The hint bit.
r (int) – An integer in the range [0, q-1].

Returns:

The adjusted high bit.

Return type:

int

Raises:

TypeError – If h is not a boolean.
TypeError – If r is not an integer.