| Subject: | $ctx->digest doesn't reset the digest state |
| Date: | Mon, 07 Dec 2009 22:43:32 -0800 |
| To: | bug-Digest-Skein [...] rt.cpan.org |
| From: | Corey Hickey <bugfood-c [...] fatooh.org> |
Hello,
Thanks for providing Digest::Skein. It seems to work nicely, except for
a bug I think I found. When I call the digest() method, I would expect
the digest state to be reset as written in the Digest documentation:
------------------------------------------------------------------------
Note that the "digest" operation is effectively a destructive, read-once
operation. Once it has been performed, the $ctx object is automatically
reset" and can be used to calculate another digest value. Call
$ctx->clone->digest if you want to calculate the digest without
resetting the digest state.
------------------------------------------------------------------------
Digest::SHA1 and Digest::MD5 work that way, at least. With
Digest::Skein, however, I get a different value the second time if I try
to hash the same data twice without manually calling the reset() method.
I've attached a small test script that illustrates the problem; it emits
the following text:
------------------------------------------------------------------------
Show quoted text
--------- testing Skein 256 ---------
initial hash of data with new context:
8a62e0aa350e48167888bce63cbe19dbe6f7050a741b9aea9a71fcadae3135bd
second hash of same data:
015b19fef178954ccb1b0475010b5b0faf48a4353d57ec6d8e4aeced698af631
hash of data after reset:
8a62e0aa350e48167888bce63cbe19dbe6f7050a741b9aea9a71fcadae3135bd
--------- testing SHA1 ---------
initial hash of data with new context:
0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33
second hash of same data:
0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33
hash of data after reset:
0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33
------------------------------------------------------------------------
Notice how the second Skein hash is different from the other two, but
all three SHA1 hashes are the same. Is this a bug or am I doing
something dumb?
In case they're relevant, here are a few system details:
Debian Sid
Linux 2.6.31.4
Perl 5.10.1
GCC 4.3.4
all 64-bit
Thanks again,
Corey
#!/usr/bin/perl
use strict;
use warnings;
use bytes;
use Digest::Skein;
use Digest::SHA1;
my $data = 'foo';
print "--------- testing Skein 256 ---------\n";
my $ctx = Digest::Skein->new(256);
test_hash($ctx, $data);
print "\n--------- testing SHA1 ---------\n";
$ctx = Digest::SHA1->new();
test_hash($ctx, $data);
sub test_hash {
my $ctx = shift;
my $data = shift;
print " initial hash of data with new context:\n";
print_hash($ctx, $data);
print " second hash of same data:\n";
print_hash($ctx, $data);
print " hash of data after reset:\n";
$ctx->reset;
print_hash($ctx, $data);
}
sub print_hash {
my $ctx = shift;
my $data = shift;
$ctx->add($data);
print $ctx->hexdigest, "\n";
}