On Wed, Mar 19, 2025 at 10:14 AM Jim Fenton <fen...@bluepopcorn.net> wrote:
> I’d still be concerned about the confidentiality of the bcc recipient > addresses. If a recipient wanted to ask, “Did Bob get bcc’ed on this?” they > could potentially find out by trying to add Bob’s email address and seeing > if the hash matched. > I don't understand how that attack would work. Imagine the signature validates with, let's say, the visible set of recipients only. To ask your question, I also feed it the Bob address. That means what gets fed to the hash changes, which would invalidate the signature, and I can't learn anything from it. Can you illustrate? -MSK
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