[OASIS Issue Tracker] Created: (OFFICE-2723) ODF 1.2 Part 33.4.2(3) Blowfish CFB Frame Size Not Specified

ODF 1.2 Part 3 3.4.2(3) Blowfish CFB Frame Size Not Specified
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                 Key: OFFICE-2723
                 URL: http://tools.oasis-open.org/issues/browse/OFFICE-2723
             Project: OASIS Open Document Format for Office Applications (OpenDocument) TC
          Issue Type: Bug
          Components: Packaging, Security
    Affects Versions: ODF 1.2 Part 3 CD 1
         Environment: This issue applies to all versions of ODF since ODF 1.0.  The specific section and wording is that of ODF 1.2 Part 3 CD01-rev08 (and the approved form, ODF 1.2 CD05 Part 3).
            Reporter: Dennis Hamilton
             Fix For: ODF 1.2 Part 3 CD 2


In Part 3 section 3.4.2(3), it is stated that encryption (and the corresponding decryption) use "the Blowfish algorithm in cipher feedback (CFB) mode (see [Blowfish])."

CFB mode is described in section 9.6 Cipher-Feedback Mode of [Blowfish].  CFB mode provides for encryption in different frame sizes up to the block size of the encryption algorithm.  In the case of Blowfish, the block size is 64 bits.  Different CFB frame sizes (e.g., 1, 8, 16, and 32 bits) do not result in the same ciphertext.

To decrypt a file encrypted with CFB, it is necessary to know the frame size that was used for the encryption.  If the frame size is not one that exactly divides 8, it must also be know how the last octets of the ciphertext are produced such that the ciphertext is of the same size as the original plaintext or how the exact plaintext size is to be recovered.

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