<?php
function my_password_form() {
    global $post;
    $label = 'pwbox-'.( empty( $post->ID ) ? rand() : $post->ID );
    $o = '<form action="' . esc_url( site_url( 'wp-login.php?action=postpass', 'login_post' ) ) . '" method="post">
    ' . __( "To view this protected post, enter the password below:" ) . '
    <label for="' . $label . '">' . __( "Password:" ) . ' </label><input name="post_password" id="' . $label . '" type="password" size="20" maxlength="20" /><input type="submit" name="Submit" value="' . esc_attr__( "Submit" ) . '" />
    </form>
    ';
    return $o;
}
add_filter( 'the_password_form', 'my_password_form' );
?>

<?php
function my_excerpt_protected( $excerpt ) {
    if ( post_password_required() )
        $excerpt = '<em>[Access to this page is password-protected.]</em>';
    return $excerpt;
}
add_filter( 'the_excerpt', 'my_excerpt_protected' );
?>