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musig: remove musig_session API docs about session ID reuse; link to Blockstream blog post

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Andrew Poelstra 2019-02-21 15:02:13 +00:00
parent 89b7f5b73b
commit f6a6bca22f
1 changed files with 3 additions and 16 deletions
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19
include/secp256k1_musig.h
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@ -19,22 +19,9 @@
* This structure is not opaque, but it MUST NOT be copied or read or written to it * This structure is not opaque, but it MUST NOT be copied or read or written to it
* directly. A signer who is online throughout the whole process and can keep this * directly. A signer who is online throughout the whole process and can keep this
* structure in memory can use the provided API functions for a safe standard * structure in memory can use the provided API functions for a safe standard
* workflow. * workflow. See https://blockstream.com/2019/02/18/musig-a-new-multisignature-standard/
* * for more details about the risks associated with serializing or deserializing this
* A signer who goes offline and needs to import/export or save/load this structure * structure.
* **must** take measures prevent replay attacks wherein an old state is loaded and
* the signing protocol forked from that point. One straightforward way to accomplish
* this is to attach the output of a monotonic non-resettable counter (hardware
* support is needed for this). Increment the counter before each output and
* encrypt+sign the entire package. If a package is deserialized with an old counter
* state or bad signature it should be rejected.
*
* Observe that an independent counter is needed for each concurrent signing session
* such a device is involved in. To avoid fragility, it is therefore recommended that
* any offline signer be usable for only a single session at once.
*
* Given access to such a counter, its output should be used as (or mixed into) the
* session ID to ensure uniqueness.
* *
* Fields: * Fields:
* combined_pk: MuSig-computed combined public key * combined_pk: MuSig-computed combined public key