RE: [office] [OASIS Issue Tracker] Updated: (OFFICE-2722) ODF 1.2Part 3 3.4.1 Plaintext and Ciphertext Same Size?

[David LeBlanc <dleblanc@exchange.microsoft.com>]

You should not assume that ciphertext and plaintext are the same size. There are three cases where this may not be true:

1) input block size and output block size differ, which is a corner case, as no commonly used symmetric algorithms have this property that I'm aware of. It wouldn't be a bad thing to constrain the problem to input block size == output block size.

2) plain text % block size != 0, so you end up with extra

3) Some chaining modes can end up with an extra block on the end.

It is desirable to know the size of the plain-text, which in this case would be the compressed size.

________________________________________
From: OASIS Issues Tracker [workgroup_mailer@lists.oasis-open.org]
Sent: Tuesday, August 03, 2010 7:22 PM
To: office@lists.oasis-open.org
Subject: [office] [OASIS Issue Tracker] Updated: (OFFICE-2722) ODF 1.2 Part 3 3.4.1 Plaintext and Ciphertext Same Size?

     [ http://tools.oasis-open.org/issues/browse/OFFICE-2722?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dennis Hamilton updated OFFICE-2722:
------------------------------------

          Component/s: Part 3 (Packages)
        Fix Version/s: ODF 1.2 CD 06
                           (was: ODF 1.2 Part 3 CD 2)
    Affects Version/s: ODF 1.2 CD 05
                           (was: ODF 1.2 Part 3 CD 1)

> ODF 1.2 Part 3 3.4.1 Plaintext and Ciphertext Same Size?
> --------------------------------------------------------
>
>                 Key: OFFICE-2722
>                 URL: http://tools.oasis-open.org/issues/browse/OFFICE-2722
>             Project: OASIS Open Document Format for Office Applications (OpenDocument) TC
>          Issue Type: Bug
>          Components: Packaging, Part 3 (Packages), Security
>    Affects Versions: ODF 1.2 CD 05
>         Environment: This issue applies specifically to section 3.4.1 of ODF 1.2 Part 3 CD01-rev08 and the ODF 1.2 CD05 Part 3 approved form.  The question also applies to ODF 1.0/1.1/IIS 26300.
>            Reporter: Dennis Hamilton
>             Fix For: ODF 1.2 CD 06
>
>
> In the third paragraph of section 3.4.1 on General Encryption provisions, it is stated that the uncompressed file size of the deflated file data (the plaintext) is saved in the corresponding <manifest:file-entry> manifest:size attribute value.  The deflated file data is replaced by the encryption (ciphertext) of the deflated file data, the entry is changed to STORED and the size of the encrypted file is then carried in those places where the file's real size value is carried.
> 1. Why is flagging as STORED asserted for the Zipped file's central directory entry and no other place, although the ciphertext size is placed in all applicable places?
> 2. There is no indication of how the size of the plaintext deflated file is to be recovered.  Is it to be assumed that the ciphertext size is the same as the size of the plaintext deflated size, so there is no need to recover it separately?

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