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nettle
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2b9b43ce
Commit
2b9b43ce
authored
Jul 06, 2014
by
Niels Möller
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eccdata: Use separate is_zero flag to represent the neutral element.
parent
51a22f02
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2 changed files
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40 additions
and
24 deletions
+40
-24
ChangeLog
ChangeLog
+5
-0
eccdata.c
eccdata.c
+35
-24
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ChangeLog
View file @
2b9b43ce
2014-07-06 Niels Möller <nisse@lysator.liu.se>
* eccdata.c: Use separate is_zero flag to represent the neutral
element.
2014-07-04 Niels Möller <nisse@lysator.liu.se>
* ecc-25519.c: New file.
...
...
eccdata.c
View file @
2b9b43ce
...
...
@@ -40,12 +40,11 @@
#include "mini-gmp.c"
/* Affine coordinates, for simplicity. Infinity point represented as x
== y == 0. FIXME: Doesn't quite work for Montgomery curves, where
(0,0) is a normal finite point. Shouldn't occur in these
computations, though. */
/* Affine coordinates, for simplicity. Infinity point, i.e., te
neutral group element, is represented as is_zero. */
struct
ecc_point
{
int
is_zero
;
mpz_t
x
;
mpz_t
y
;
};
...
...
@@ -107,25 +106,26 @@ ecc_clear (struct ecc_point *p)
static
int
ecc_zero_p
(
const
struct
ecc_point
*
p
)
{
return
mpz_sgn
(
p
->
x
)
==
0
&&
mpz_sgn
(
p
->
y
)
==
0
;
return
p
->
is_zero
;
}
static
int
ecc_equal_p
(
const
struct
ecc_point
*
p
,
const
struct
ecc_point
*
q
)
{
return
mpz_cmp
(
p
->
x
,
q
->
x
)
==
0
&&
mpz_cmp
(
p
->
y
,
q
->
y
)
==
0
;
return
p
->
is_zero
?
q
->
is_zero
:
!
q
->
is_zero
&&
mpz_cmp
(
p
->
x
,
q
->
x
)
==
0
&&
mpz_cmp
(
p
->
y
,
q
->
y
)
==
0
;
}
static
void
ecc_set_zero
(
struct
ecc_point
*
r
)
{
mpz_set_ui
(
r
->
x
,
0
);
mpz_set_ui
(
r
->
y
,
0
);
r
->
is_zero
=
1
;
}
static
void
ecc_set
(
struct
ecc_point
*
r
,
const
struct
ecc_point
*
p
)
{
r
->
is_zero
=
p
->
is_zero
;
mpz_set
(
r
->
x
,
p
->
x
);
mpz_set
(
r
->
y
,
p
->
y
);
}
...
...
@@ -186,9 +186,10 @@ ecc_dup (const struct ecc_curve *ecc,
mpz_sub
(
y
,
y
,
p
->
y
);
mpz_mod
(
y
,
y
,
ecc
->
p
);
r
->
is_zero
=
0
;
mpz_swap
(
x
,
r
->
x
);
mpz_swap
(
y
,
r
->
y
);
mpz_clear
(
m
);
mpz_clear
(
t
);
mpz_clear
(
x
);
...
...
@@ -243,6 +244,7 @@ ecc_add (const struct ecc_curve *ecc,
mpz_sub
(
y
,
y
,
p
->
y
);
mpz_mod
(
y
,
y
,
ecc
->
p
);
r
->
is_zero
=
0
;
mpz_swap
(
x
,
r
->
x
);
mpz_swap
(
y
,
r
->
y
);
...
...
@@ -296,6 +298,7 @@ static void
ecc_set_str
(
struct
ecc_point
*
p
,
const
char
*
x
,
const
char
*
y
)
{
p
->
is_zero
=
0
;
mpz_set_str
(
p
->
x
,
x
,
16
);
mpz_set_str
(
p
->
y
,
y
,
16
);
}
...
...
@@ -506,7 +509,7 @@ ecc_curve_init (struct ecc_curve *ecc, unsigned bit_size)
case
255
:
/* curve25519, y^2 = x^3 + 486662 x^2 + x (mod p), with p = 2^{255} - 19.
Acc
c
ording to http://cr.yp.to/papers.html#newelliptic, this
According to http://cr.yp.to/papers.html#newelliptic, this
is birationally equivalent to the Edwards curve
x^2 + y^2 = 1 + (121665/121666) x^2 y^2 (mod p).
...
...
@@ -644,20 +647,30 @@ ecc_mul_pippenger (const struct ecc_curve *ecc,
mpz_clear
(
n
);
}
static
void
ecc_point_out
(
FILE
*
f
,
const
struct
ecc_point
*
p
)
{
if
(
p
->
is_zero
)
fprintf
(
f
,
"zero"
);
else
{
fprintf
(
stderr
,
"("
);
mpz_out_str
(
stderr
,
16
,
p
->
x
);
fprintf
(
stderr
,
",
\n
"
);
mpz_out_str
(
stderr
,
16
,
(
p
)
->
y
);
fprintf
(
stderr
,
")"
);
}
}
#define ASSERT_EQUAL(p, q) do { \
if (!ecc_equal_p (p, q)) \
{ \
fprintf (stderr, "%s:%d: ASSERT_EQUAL (%s, %s) failed.\n", \
__FILE__, __LINE__, #p, #q); \
fprintf (stderr, "p = ("); \
mpz_out_str (stderr, 16, (p)->x); \
fprintf (stderr, ",\n "); \
mpz_out_str (stderr, 16, (p)->y); \
fprintf (stderr, ")\nq = ("); \
mpz_out_str (stderr, 16, (q)->x); \
fprintf (stderr, ",\n "); \
mpz_out_str (stderr, 16, (q)->y); \
fprintf (stderr, ")\n"); \
fprintf (stderr, "p = "); \
ecc_point_out (stderr, (p)); \
fprintf (stderr, "\nq = "); \
ecc_point_out (stderr, (q)); \
fprintf (stderr, "\n"); \
abort(); \
} \
} while (0)
...
...
@@ -667,11 +680,9 @@ ecc_mul_pippenger (const struct ecc_curve *ecc,
{ \
fprintf (stderr, "%s:%d: ASSERT_ZERO (%s) failed.\n", \
__FILE__, __LINE__, #p); \
fprintf (stderr, "p = ("); \
mpz_out_str (stderr, 16, (p)->x); \
fprintf (stderr, ",\n "); \
mpz_out_str (stderr, 16, (p)->y); \
fprintf (stderr, ")\n"); \
fprintf (stderr, "p = "); \
ecc_point_out (stderr, (p)); \
fprintf (stderr, "\n"); \
abort(); \
} \
} while (0)
...
...
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