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RE: Literal packets and canonicalization

2004-05-21 08:22:24

I understand that line endings need to be converted to CRLF. But what about 
trailing whitespace? When canonicalizing the literal data prior to encryption, 
do we have to strip off trailing whitespaces? From the RFC, it seems that for 
signatures the canonicalization must do both, i.e convert line endings and 
strip off trailing whitespaces. But I am not sure if the same needs to be done 
for encrypting text data.

        -----Original Message----- 
        From: owner-ietf-openpgp(_at_)mail(_dot_)imc(_dot_)org on behalf of 
David Shaw 
        Sent: Thu 5/6/2004 4:49 PM 
        To: ietf-openpgp(_at_)imc(_dot_)org 
        Subject: Re: Literal packets and canonicalization

        On Thu, May 06, 2004 at 04:27:49PM -0400, Hasnain Mujtaba wrote:
        > Thank you for the answer David. If, as the RFC states, we canoncialize
        > the data before storing it in the literal packet, then the
        > implementation is tampering with the file before performing the
        > operation, say encryption.
        "Tampering" is perhaps a little strong.  The canonicalization is part
        of the standard, so while it may be tampering, it's legal
        tampering. ;)
        > When I use GPG to encrypt and decrypt a text file, the checksums of
        > the source text file and the decrypted file are the same. So, the
        > file in not being canonicalized prior to encryption?
        Maybe, maybe not.  If you are encrypting and decrypting that text file
        on the same platform, then you would expect to end up with the same
        file since the data is canonicalized on the way in, and
        decanonicalized on the way out.
        Alternately, if you specified the text file as binary, then no
        canonicalization is done.
        GnuPG uses the "--textmode" switch to turn on canonicalization.  PGP
        has a checkbox for it named something like "Input is text".