Re: [Webpush] Versioning aes128gcm-encoded messages

Martin Thomson <martin.thomson@gmail.com> Mon, 20 March 2017 00:52 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Mon, 20 Mar 2017 11:52:37 +1100
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To: Kit Cambridge <kit@mozilla.com>
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Subject: Re: [Webpush] Versioning aes128gcm-encoded messages
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My intent was to signal version with the content-coding type.

Adding a magic number doesn't really add anything unless you wanted to
sanity check before doing a decryption.  The decryption will fail if
something has changed and decryption is cheap enough not to need an
redundant version signal.

On 20 March 2017 at 11:04, Kit Cambridge <kit@mozilla.com> wrote:
> Hi,
>
> Now that encrypted content-coding has a binary header block, should we
> consider including a "magic number" prefix with a version? This would avoid
> having to use a new scheme name for backward-incompatible changes (so far,
> we've gone through "aesgcm", "aesgcm128", and "aes128gcm"), and make it
> easier for tools to identify encrypted payloads.
>
> OTOH, it seems like the draft has crystallized enough to where this won't be
> necessary. In the future, maybe it does make sense to use a new scheme name
> for substantial changes.
>
> I'm also not sure how useful identifying encrypted messages is, given that
> their payloads (by design!) don't reveal anything about their contents.
>
> WDYT?
>
> - kit
>
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