[Konstantinos]

pawn Код:

// Load the password before.
// PlayerInfo[playerid][Password] should be string and be in the enum:

// Password[ 129 ],

new
    buf[ 129 ]
;
WP_Hash( buf, sizeof( buf ), inputtext );
if( !strcmp( buf, PlayerInfo[ playerid ][ Password ], false ) )
{
    // Correct password
}
else
{ 
    // wrong password
}

Do the same on register.

pawn Код:

new
    buf[ 129 ]
;
WP_Hash( buf, sizeof( buf ), inputtext );

And save the buf.