Commit 47123257 authored by Manuel Pégourié-Gonnard's avatar Manuel Pégourié-Gonnard Committed by Paul Bakker
Browse files

Clarifications in comments; code cosmetics & style

parent dada4da3
......@@ -55,7 +55,15 @@ ecp_point;
* The curves we consider are defined by y^2 = x^3 - 3x + b mod p,
* and a generator for a large subgroup is fixed.
*
* modp may be NULL; pbits will not be used in this case.
* If modp is NULL, pbits will not be used, and reduction modulo P is
* done using a generic algorithm.
*
* If modp is not NULL, pbits must be the size of P in bits and modp
* must be a function that takes an mpi in the range 0..2^(2*pbits) and
* transforms it in-place in an integer of little more than pbits, so
* that the integer may be efficiently brought in the 0..P range by a
* few additions or substractions. It must return 0 on success and a
* POLARSSL_ERR_ECP_XXX error on failure.
*/
typedef struct
{
......@@ -77,7 +85,7 @@ ecp_group;
*
* \warning This library does not support validation of arbitrary domain
* parameters. Therefore, only well-known domain parameters from trusted
* sources (such as the ones below) should be used. See ecp_use_known_dp().
* sources should be used. See ecp_use_known_dp().
*/
#define POLARSSL_ECP_DP_SECP192R1 0
#define POLARSSL_ECP_DP_SECP224R1 1
......@@ -161,7 +169,7 @@ int ecp_group_read_string( ecp_group *grp, int radix,
* \param grp Destination group
* \param index Index in the list of well-known domain parameters
*
* \return O if successul,
* \return O if successful,
* POLARSSL_ERR_MPI_XXX if initialization failed
* POLARSSL_ERR_ECP_GENERIC if index is out of range
*
......
......@@ -109,11 +109,11 @@ void ecp_set_zero( ecp_point *pt )
*/
int ecp_copy( ecp_point *P, const ecp_point *Q )
{
int ret = 0;
int ret;
if( Q->is_zero ) {
ecp_set_zero( P );
return( ret );
return( 0 );
}
P->is_zero = Q->is_zero;
......@@ -130,7 +130,7 @@ cleanup:
int ecp_point_read_string( ecp_point *P, int radix,
const char *x, const char *y )
{
int ret = 0;
int ret;
P->is_zero = 0;
MPI_CHK( mpi_read_string( &P->X, radix, x ) );
......@@ -147,7 +147,7 @@ int ecp_group_read_string( ecp_group *grp, int radix,
const char *p, const char *b,
const char *gx, const char *gy, const char *n)
{
int ret = 0;
int ret;
MPI_CHK( mpi_read_string( &grp->P, radix, p ) );
MPI_CHK( mpi_read_string( &grp->B, radix, b ) );
......@@ -159,15 +159,11 @@ cleanup:
}
/*
* Wrapper around fast quasi-modp functions, with fallback to mpi_mod_mpi
*
* The quasi-modp functions expect an mpi N such that 0 <= N < 2^(2*pbits)
* and change it in-place so that it can easily be brought in the 0..P-1
* range by a few additions or substractions.
* Wrapper around fast quasi-modp functions, with fall-back to mpi_mod_mpi
*/
static int ecp_modp( mpi *N, const ecp_group *grp )
{
int ret = 0;
int ret;
if( grp->modp == NULL )
return( mpi_mod_mpi( N, N, &grp->P ) );
......@@ -206,7 +202,7 @@ cleanup:
*/
static int ecp_mod_p521( mpi *N )
{
int ret = 0;
int ret;
t_uint Mp[P521_SIZE_INT];
mpi M;
......@@ -353,13 +349,13 @@ int ecp_use_known_dp( ecp_group *grp, size_t index )
}
/*
* Fast mod-p functions expect an argument in the 0 .. p^2 range.
* Fast mod-p functions expect their argument to be in the 0..p^2 range.
*
* In order to garantee that, we need to ensure that operands of
* mpi_mul_mpi are in the 0 .. p range. So, after each operation we will
* In order to guarantee that, we need to ensure that operands of
* mpi_mul_mpi are in the 0..p range. So, after each operation we will
* bring the result back to this range.
*
* The following macros are helpers for that.
* The following macros are shortcuts for doing that.
*/
/*
......@@ -412,7 +408,7 @@ static void ecp_ptjac_free( ecp_ptjac *P )
*/
static int ecp_ptjac_copy( ecp_ptjac *R, const ecp_ptjac *P )
{
int ret = 0;
int ret;
MPI_CHK( mpi_copy( &R->X, &P->X ) );
MPI_CHK( mpi_copy( &R->Y, &P->Y ) );
......@@ -427,7 +423,7 @@ cleanup:
*/
static int ecp_ptjac_set_zero( ecp_ptjac *P )
{
int ret = 0;
int ret;
MPI_CHK( mpi_lset( &P->X, 1 ) );
MPI_CHK( mpi_lset( &P->Y, 1 ) );
......@@ -442,7 +438,7 @@ cleanup:
*/
static int ecp_aff_to_jac( ecp_ptjac *jac, const ecp_point *aff )
{
int ret = 0;
int ret;
if( aff->is_zero )
return( ecp_ptjac_set_zero( jac ) );
......@@ -461,7 +457,7 @@ cleanup:
static int ecp_jac_to_aff( const ecp_group *grp,
ecp_point *aff, const ecp_ptjac *jac )
{
int ret = 0;
int ret;
mpi Zi, ZZi, T;
if( mpi_cmp_int( &jac->Z, 0 ) == 0 ) {
......@@ -499,7 +495,7 @@ cleanup:
static int ecp_double_jac( const ecp_group *grp, ecp_ptjac *R,
const ecp_ptjac *P )
{
int ret = 0;
int ret;
mpi T1, T2, T3, X, Y, Z;
if( mpi_cmp_int( &P->Z, 0 ) == 0 )
......@@ -508,17 +504,16 @@ static int ecp_double_jac( const ecp_group *grp, ecp_ptjac *R,
mpi_init( &T1 ); mpi_init( &T2 ); mpi_init( &T3 );
mpi_init( &X ); mpi_init( &Y ); mpi_init( &Z );
MPI_CHK( mpi_mul_mpi( &T1, &P->Z, &P->Z ) ); MOD_MUL( T1 );
MPI_CHK( mpi_sub_mpi( &T2, &P->X, &T1 ) ); MOD_SUB( T2 );
MPI_CHK( mpi_add_mpi( &T1, &P->X, &T1 ) ); MOD_ADD( T1 );
MPI_CHK( mpi_mul_mpi( &T2, &T2, &T1 ) ); MOD_MUL( T2 );
MPI_CHK( mpi_mul_int( &T2, &T2, 3 ) ); MOD_ADD( T2 );
MPI_CHK( mpi_copy ( &Y, &P->Y ) );
MPI_CHK( mpi_shift_l( &Y, 1 ) ); MOD_ADD( Y );
MPI_CHK( mpi_mul_mpi( &Z, &Y, &P->Z ) ); MOD_MUL( Z );
MPI_CHK( mpi_mul_mpi( &Y, &Y, &Y ) ); MOD_MUL( Y );
MPI_CHK( mpi_mul_mpi( &T3, &Y, &P->X ) ); MOD_MUL( T3 );
MPI_CHK( mpi_mul_mpi( &Y, &Y, &Y ) ); MOD_MUL( Y );
MPI_CHK( mpi_mul_mpi( &T1, &P->Z, &P->Z ) ); MOD_MUL( T1 );
MPI_CHK( mpi_sub_mpi( &T2, &P->X, &T1 ) ); MOD_SUB( T2 );
MPI_CHK( mpi_add_mpi( &T1, &P->X, &T1 ) ); MOD_ADD( T1 );
MPI_CHK( mpi_mul_mpi( &T2, &T2, &T1 ) ); MOD_MUL( T2 );
MPI_CHK( mpi_mul_int( &T2, &T2, 3 ) ); MOD_ADD( T2 );
MPI_CHK( mpi_mul_int( &Y, &P->Y, 2 ) ); MOD_ADD( Y );
MPI_CHK( mpi_mul_mpi( &Z, &Y, &P->Z ) ); MOD_MUL( Z );
MPI_CHK( mpi_mul_mpi( &Y, &Y, &Y ) ); MOD_MUL( Y );
MPI_CHK( mpi_mul_mpi( &T3, &Y, &P->X ) ); MOD_MUL( T3 );
MPI_CHK( mpi_mul_mpi( &Y, &Y, &Y ) ); MOD_MUL( Y );
/*
* For Y = Y / 2 mod p, we must make sure that Y is even before
......@@ -528,13 +523,12 @@ static int ecp_double_jac( const ecp_group *grp, ecp_ptjac *R,
MPI_CHK( mpi_add_mpi( &Y, &Y, &grp->P ) );
MPI_CHK( mpi_shift_r( &Y, 1 ) );
MPI_CHK( mpi_mul_mpi( &X, &T2, &T2 ) ); MOD_MUL( X );
MPI_CHK( mpi_copy ( &T1, &T3 ) );
MPI_CHK( mpi_shift_l( &T1, 1 ) ); MOD_ADD( T1 );
MPI_CHK( mpi_sub_mpi( &X, &X, &T1 ) ); MOD_SUB( X );
MPI_CHK( mpi_sub_mpi( &T1, &T3, &X ) ); MOD_SUB( T1 );
MPI_CHK( mpi_mul_mpi( &T1, &T1, &T2 ) ); MOD_MUL( T1 );
MPI_CHK( mpi_sub_mpi( &Y, &T1, &Y ) ); MOD_SUB( Y );
MPI_CHK( mpi_mul_mpi( &X, &T2, &T2 ) ); MOD_MUL( X );
MPI_CHK( mpi_mul_int( &T1, &T3, 2 ) ); MOD_ADD( T1 );
MPI_CHK( mpi_sub_mpi( &X, &X, &T1 ) ); MOD_SUB( X );
MPI_CHK( mpi_sub_mpi( &T1, &T3, &X ) ); MOD_SUB( T1 );
MPI_CHK( mpi_mul_mpi( &T1, &T1, &T2 ) ); MOD_MUL( T1 );
MPI_CHK( mpi_sub_mpi( &Y, &T1, &Y ) ); MOD_SUB( Y );
MPI_CHK( mpi_copy( &R->X, &X ) );
MPI_CHK( mpi_copy( &R->Y, &Y ) );
......@@ -554,7 +548,7 @@ cleanup:
static int ecp_add_mixed( const ecp_group *grp, ecp_ptjac *R,
const ecp_ptjac *P, const ecp_point *Q )
{
int ret = 0;
int ret;
mpi T1, T2, T3, T4, X, Y, Z;
/*
......@@ -569,12 +563,12 @@ static int ecp_add_mixed( const ecp_group *grp, ecp_ptjac *R,
mpi_init( &T1 ); mpi_init( &T2 ); mpi_init( &T3 ); mpi_init( &T4 );
mpi_init( &X ); mpi_init( &Y ); mpi_init( &Z );
MPI_CHK( mpi_mul_mpi( &T1, &P->Z, &P->Z ) ); MOD_MUL( T1 );
MPI_CHK( mpi_mul_mpi( &T2, &T1, &P->Z ) ); MOD_MUL( T2 );
MPI_CHK( mpi_mul_mpi( &T1, &T1, &Q->X ) ); MOD_MUL( T1 );
MPI_CHK( mpi_mul_mpi( &T2, &T2, &Q->Y ) ); MOD_MUL( T2 );
MPI_CHK( mpi_sub_mpi( &T1, &T1, &P->X ) ); MOD_SUB( T1 );
MPI_CHK( mpi_sub_mpi( &T2, &T2, &P->Y ) ); MOD_SUB( T2 );
MPI_CHK( mpi_mul_mpi( &T1, &P->Z, &P->Z ) ); MOD_MUL( T1 );
MPI_CHK( mpi_mul_mpi( &T2, &T1, &P->Z ) ); MOD_MUL( T2 );
MPI_CHK( mpi_mul_mpi( &T1, &T1, &Q->X ) ); MOD_MUL( T1 );
MPI_CHK( mpi_mul_mpi( &T2, &T2, &Q->Y ) ); MOD_MUL( T2 );
MPI_CHK( mpi_sub_mpi( &T1, &T1, &P->X ) ); MOD_SUB( T1 );
MPI_CHK( mpi_sub_mpi( &T2, &T2, &P->Y ) ); MOD_SUB( T2 );
if( mpi_cmp_int( &T1, 0 ) == 0 )
{
......@@ -590,18 +584,18 @@ static int ecp_add_mixed( const ecp_group *grp, ecp_ptjac *R,
}
}
MPI_CHK( mpi_mul_mpi( &Z, &P->Z, &T1 ) ); MOD_MUL( Z );
MPI_CHK( mpi_mul_mpi( &T3, &T1, &T1 ) ); MOD_MUL( T3 );
MPI_CHK( mpi_mul_mpi( &T4, &T3, &T1 ) ); MOD_MUL( T4 );
MPI_CHK( mpi_mul_mpi( &T3, &T3, &P->X ) ); MOD_MUL( T3 );
MPI_CHK( mpi_mul_int( &T1, &T3, 2 ) ); MOD_ADD( T1 );
MPI_CHK( mpi_mul_mpi( &X, &T2, &T2 ) ); MOD_MUL( X );
MPI_CHK( mpi_sub_mpi( &X, &X, &T1 ) ); MOD_SUB( X );
MPI_CHK( mpi_sub_mpi( &X, &X, &T4 ) ); MOD_SUB( X );
MPI_CHK( mpi_sub_mpi( &T3, &T3, &X ) ); MOD_SUB( T3 );
MPI_CHK( mpi_mul_mpi( &T3, &T3, &T2 ) ); MOD_MUL( T3 );
MPI_CHK( mpi_mul_mpi( &T4, &T4, &P->Y ) ); MOD_MUL( T4 );
MPI_CHK( mpi_sub_mpi( &Y, &T3, &T4 ) ); MOD_SUB( Y );
MPI_CHK( mpi_mul_mpi( &Z, &P->Z, &T1 ) ); MOD_MUL( Z );
MPI_CHK( mpi_mul_mpi( &T3, &T1, &T1 ) ); MOD_MUL( T3 );
MPI_CHK( mpi_mul_mpi( &T4, &T3, &T1 ) ); MOD_MUL( T4 );
MPI_CHK( mpi_mul_mpi( &T3, &T3, &P->X ) ); MOD_MUL( T3 );
MPI_CHK( mpi_mul_int( &T1, &T3, 2 ) ); MOD_ADD( T1 );
MPI_CHK( mpi_mul_mpi( &X, &T2, &T2 ) ); MOD_MUL( X );
MPI_CHK( mpi_sub_mpi( &X, &X, &T1 ) ); MOD_SUB( X );
MPI_CHK( mpi_sub_mpi( &X, &X, &T4 ) ); MOD_SUB( X );
MPI_CHK( mpi_sub_mpi( &T3, &T3, &X ) ); MOD_SUB( T3 );
MPI_CHK( mpi_mul_mpi( &T3, &T3, &T2 ) ); MOD_MUL( T3 );
MPI_CHK( mpi_mul_mpi( &T4, &T4, &P->Y ) ); MOD_MUL( T4 );
MPI_CHK( mpi_sub_mpi( &Y, &T3, &T4 ) ); MOD_SUB( Y );
MPI_CHK( mpi_copy( &R->X, &X ) );
MPI_CHK( mpi_copy( &R->Y, &Y ) );
......@@ -621,7 +615,7 @@ cleanup:
int ecp_add( const ecp_group *grp, ecp_point *R,
const ecp_point *P, const ecp_point *Q )
{
int ret = 0;
int ret;
ecp_ptjac J;
ecp_ptjac_init( &J );
......@@ -643,20 +637,20 @@ cleanup:
int ecp_mul( const ecp_group *grp, ecp_point *R,
const mpi *m, const ecp_point *P )
{
int ret = 0;
int ret;
size_t pos;
ecp_ptjac Q[2];
ecp_ptjac_init( &Q[0] ); ecp_ptjac_init( &Q[1] );
/*
* The general method works only for m >= 1
*/
if( mpi_cmp_int( m, 0 ) == 0 ) {
ecp_set_zero( R );
goto cleanup;
return( 0 );
}
ecp_ptjac_init( &Q[0] ); ecp_ptjac_init( &Q[1] );
ecp_ptjac_set_zero( &Q[0] );
for( pos = mpi_msb( m ) - 1 ; ; pos-- )
......
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