docs: update sender verification spec to draft 1.0#22
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Swaagie
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JWS header-only signing over From, Date, Subject, Message-ID, To, Cc, Reply-To, In-Reply-To, and References. Log seals hashes only; full binding travels with the email. Salted hashes for sender addresses in public logs. Strict-mode DNS flag for Tier 1 enforcement. Body hash RECOMMENDED for Tier 1 senders with gateway handling options. DKIM comparison section. Privacy extensions from ANS Trust Index. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
Updates SENDER_VERIFICATION_SPEC.md to v1.0 and updates README.md.
The signed header set covers From, Date, Subject, Message-ID, To, Cc,
Reply-To, In-Reply-To, and References. To and Cc prevent replay to
unintended recipients. Reply-To prevents response redirection. In-Reply-To
and References prevent thread hijacking, where an attacker forges a reply
into an existing invoice conversation.
The log seals hashes only. The full binding (public key, owner, constraints)
travels with the email in the Sender-Verification header. Sender addresses
are stored as salted hashes in public logs. A strict-mode DNS flag lets
domains declare that Tier 1 senders must always carry the header.
Body hash is RECOMMENDED for Tier 1 senders. Gateways that see the body
hash can either preserve the body intact or verify the hash before applying
URL rewrites and banners.
Existing PGP key pairs can be registered in the log without generating new
keys. The DKIM comparison section explains what happens when a domain is
compromised under each model. Privacy extensions reference the ANS Trust
Index for query privacy and zero-knowledge freshness.
Test plan
Generated with Claude Code