Cryptography Reference
In-Depth Information
modular addition of a
CLINT
type and a
USHORT
type
Function:
int umadd_l (CLINT a_l, USHORT b, CLINT c_l,
CLINT m_l);
Syntax:
a_l, b
(summands),
m_l
(modulus)
Input:
c_l
(remainder)
Output:
E_CLINT_OK
if all is ok
E_CLINT_DBZ
if division by 0
Return:
int
umadd_l (CLINT a_l, USHORT b, CLINT c_l, CLINT m_l)
{
int err;
CLINT tmp_l;
u2clint_l (tmp_l, b);
err = madd_l (a_l, tmp_l, c_l, m_l);
return err;
}
Our collection of mixed functions with a
USHORT
argument will be extended in
the following chapter to include two further functions. To end this chapter we
would like, with the help of modular subtraction, to construct an additional
useful auxiliary function that determines whether two
CLINT
values are equal as
representatives of a residue class modulo
m
. The following function
mequ_l()
accomplishes this by using the definition of the congruence relationship
a ≡ b
mod
m ⇐⇒ m |
(
a − b
)
.
To determine whether two
CLINT
objects
a_l
and
b_l
are equivalent modulo
m_l
, we need do nothing further than apply
msub_l(a_l, b_l, r_l, m_l)
and
check whether the remainder
r_l
of this operation is equal to zero.
test for equivalence modulo
m
Function:
int mequ_l (CLINT a_l, CLINT b_l, CLINT m_l);
Syntax:
Input:
a_l, b_l
(operands),
m_l
(modulus)
1if
(a_l == b_l)
modulo
m_l
0
otherwise
Return:
