Re: Padding Problem UPDATE (Still broken)
- From: Jim Gibson <jgibson@xxxxxxxxxxxxxxxxx>
- Date: Fri, 12 Aug 2005 16:20:16 -0700
In article <r_adnYren7jDkWDfRVn-uw@xxxxxxxxxxx>, Hal Vaughan
<hal@xxxxxxxxxxxxxxxxxxxx> wrote:
> Hal Vaughan wrote:
>
>
[problem description snipped]
> I found the "padding" setting, and now use this to encrypt:
>
> $cipher = Crypt::CBC->new( { 'key' => $key, iv => $vector,
> prepend_iv => 0, 'cipher' => 'Blowfish', 'regenerate_key' => 0,
> padding => 'standard' });
> $data = $cipher->encrypt($rawdata);
>
> And now I get a different error on the Java end:
>
> javax.crypto.BadPaddingException: Given final block not properly padded
>
> So now it's padding properly (which is should have done anyway, since it is
> supposed to default to "standard") but the last block is not being padded
> properly. At first I thought I had to change and use the sequence of
> "start, crypt, finish" for encoding, but according to the docs, encrypt()
> does it all. So is there something I can do to make sure the last block is
> padded? Apparently Crypt::CBC isn't doing that.
Have you tried the other values of the padding setting ('space',
'onesandzeroes', 'null')?
Padding applies only to the last block. Block cipher algorithms like
Blowfish work on blocks of bits. Blowfish uses blocks of size 64 bits.
If the last block is short, padding is added to make it a full block.
The 'standard' padding method is to add 1 to 8 bytes, depending upon
the length of the original data, each byte containing the number of
bytes being added. That way the padding bytes may be unambiguously
removed from the decrypted message. Note that if your message is a
multiple of 64 bits, an extra block of '0808080808080808' will be
added. All of this is explained in the documentation for Crpyt::CBC and
in the references below.
You might try 'null' or 'spaces' on the Perl side and
'Blowfish/CBC/Nopadding' on the Java side. I have not used either
Crypt::CBC nor javax.crypto, so can't give much additional help.
References:
<http://www.faqs.org/rfcs/rfc1423.html>
<http://java.sun.com/j2se/1.4.2/docs/guide/security/jce/JCERefGuide.html
#AppA>
----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! >100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---
.
- Follow-Ups:
- Re: Padding Problem UPDATE (Still broken)
- From: Hal Vaughan
- Re: Padding Problem UPDATE (Still broken)
- References:
- Padding Problem with Blowfish and Crypt::CBC and Java Cipher
- From: Hal Vaughan
- Re: Padding Problem UPDATE (Still broken)
- From: Hal Vaughan
- Padding Problem with Blowfish and Crypt::CBC and Java Cipher
- Prev by Date: Re: lc() with undefined arg
- Next by Date: FAQ 3.20 How can I hide the source for my Perl program?
- Previous by thread: Re: Padding Problem UPDATE (Still broken)
- Next by thread: Re: Padding Problem UPDATE (Still broken)
- Index(es):
Relevant Pages
|
|
