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02c617a9
Commit
02c617a9
authored
Aug 23, 2014
by
Niels Möller
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Document and test that ecc_modp_inv produces 0 for input a == 0 (mod p).
parent
752861f7
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ChangeLog
ChangeLog
+8
-0
sec-modinv.c
sec-modinv.c
+1
-0
testsuite/ecc-modinv-test.c
testsuite/ecc-modinv-test.c
+41
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ChangeLog
View file @
02c617a9
2014-08-23 Niels Möller <nisse@lysator.liu.se>
* sec-modinv.c (sec_modinv): Document that for a == 0 (mod m), we
should produce the "inverse" 0.
* testsuite/ecc-modinv-test.c (test_main): Check that ecc_modp_inv
produces 0 if a == 0 or a == p.
2014-08-22 Niels Möller <nisse@lysator.liu.se>
* x86_64/ecc-25519-modp.asm: New file. Assembly implementation,
...
...
sec-modinv.c
View file @
02c617a9
...
...
@@ -71,6 +71,7 @@ cnd_swap (int cnd, mp_limb_t *ap, mp_limb_t *bp, mp_size_t n)
}
/* Compute a^{-1} mod m, with running time depending only on the size.
Returns zero if a == 0 (mod m), to be consistent with a^{phi(m)-1}.
Also needs (m+1)/2, and m must be odd. */
void
sec_modinv
(
mp_limb_t
*
vp
,
mp_limb_t
*
ap
,
mp_size_t
n
,
...
...
testsuite/ecc-modinv-test.c
View file @
02c617a9
...
...
@@ -37,6 +37,17 @@ ref_modinv (mp_limb_t *rp, const mp_limb_t *ap, const mp_limb_t *mp, mp_size_t m
#define MAX_ECC_SIZE (1 + 521 / GMP_NUMB_BITS)
#define COUNT 500
static
int
mpn_zero_p
(
mp_srcptr
ap
,
mp_size_t
n
)
{
while
(
--
n
>=
0
)
{
if
(
ap
[
n
]
!=
0
)
return
0
;
}
return
1
;
}
void
test_main
(
void
)
{
...
...
@@ -55,6 +66,36 @@ test_main (void)
{
const
struct
ecc_curve
*
ecc
=
ecc_curves
[
i
];
unsigned
j
;
/* Check behaviour for zero input */
mpn_zero
(
a
,
ecc
->
size
);
memset
(
ai
,
17
,
ecc
->
size
*
sizeof
(
*
ai
));
ecc_modp_inv
(
ecc
,
ai
,
a
,
scratch
);
if
(
!
mpn_zero_p
(
ai
,
ecc
->
size
))
{
fprintf
(
stderr
,
"ecc_modp_inv failed for zero input (bit size %u):
\n
"
,
ecc
->
bit_size
);
gmp_fprintf
(
stderr
,
"p = %Nx
\n
"
"t = %Nx (bad)
\n
"
,
ecc
->
p
,
ecc
->
size
,
ai
,
ecc
->
size
);
abort
();
}
/* Check behaviour for a = p */
mpn_copyi
(
a
,
ecc
->
p
,
ecc
->
size
);
memset
(
ai
,
17
,
ecc
->
size
*
sizeof
(
*
ai
));
ecc_modp_inv
(
ecc
,
ai
,
a
,
scratch
);
if
(
!
mpn_zero_p
(
ai
,
ecc
->
size
))
{
fprintf
(
stderr
,
"ecc_modp_inv failed for a = p input (bit size %u):
\n
"
,
ecc
->
bit_size
);
gmp_fprintf
(
stderr
,
"p = %Nx
\n
"
"t = %Nx (bad)
\n
"
,
ecc
->
p
,
ecc
->
size
,
ai
,
ecc
->
size
);
abort
();
}
for
(
j
=
0
;
j
<
COUNT
;
j
++
)
{
if
(
j
&
1
)
...
...
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