#!/usr/bin/perl -w

use Digest;
use Term::ReadPassword;

die "usage: twonk SALT" unless $ARGV[0];

my $salt_file = $ARGV[0];
open SALT, $salt_file or die "can't open salt: $!";

my $ctx = Digest->new('SHA-1');
my $passphrase = read_password('Passphrase: ', 10, 1) or exit 1;
$ctx->add($passphrase);

$ctx->addfile(SALT);
close SALT;

my $chars = $salt_file =~ /\.(\d+)$/ ? $1 : 10;
my $password = $ctx->b64digest();
# $password =~ tr{/+}{_-};
print substr($password, 0, $chars), "\n";