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# HIP304 - z\_signmessage + z\_verifymessage
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```
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HIP: 304
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Title: Signing and verifying messages from Sapling addresses
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Author: Duke Leto
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Category: Standards
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Created: 2020-02-02
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License: GPLv3
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```
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# Terminology
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The key words "MUST", "MUST NOT", and "MAY" in this document are to be interpreted as described in RFC 2119.
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[#RFC2119]
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# Abstract
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This is an xxx HIP describing signed Sapling messages.
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# Motivation
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TLDR: Extend the `signmessage` and `verifymessage` RPCs to Sapling shielded addresses.
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Many people, including the author, have created Github issues asking for the ability to
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sign messages with zaddrs. Originally, it was not possible with Sprout addresses but
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now Sapling zaddrs have the internal machinery to support this use case.
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# Specification
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This document specifies two new RPCs
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z_signmessage
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z_verifymessage
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which are direct shielded counterparts to the original Bitcoin RPCs:
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signmessage
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verifymessage
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This specification is directly influenced by various Zcash Github issues and ZIP304
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such as https://github.com/zcash/zcash/issues/3159 and https://github.com/zcash/zcash/issues/1770
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and the algorithm designed by Daira and other Zcash developers. We simply took the publicly
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defined algorithm and decided to actually implement it and decide any implementation details that
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would be needed along the way.
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## Internal Design
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One option would be to write a custom zk-SNARK "circuit" to support signing via a zaddr. This would
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be a large amount of work and was dismissed, reasonably, as not viable by Zcash developers.
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# References
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.. [#RFC2119] `Key words for use in RFCs to Indicate Requirement Levels <https://tools.ietf.org/html/rfc2119>`_
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.. [#BIP32] `Hierarchical Deterministic Wallets <https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki>`_
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