Module fta 

Federated trust authorities and nested threshold (SIGNATIF §10).

A federated trust authority (FTA) is a threshold group of independent organizations sharing a single aggregate key: M-of-K organizations must cooperate, and each organization may itself be a threshold authority (nested threshold). No single organization controls the authority, and an FTA may span hierarchies — its artifacts are verifiable against the FTA’s aggregate key and recognized by all member hierarchies.

Ceremony robustness (ceremony-robustness, rogue-key-prevention):

• every member demonstrates proof of possession of the private key behind its contributed share during key generation, so a malicious member cannot register a crafted key that makes the aggregate equal to its solo key;
• nonce commitment (commit-then-reveal) prevents nonce bias;
• identifiable abort attributes a failed ceremony to the member causing the failure.

Structs

AbortAttribution

Identifiable abort: which member caused a ceremony failure and why.

DkgSession

A DKG session for forming (or re-sharing) an FTA.

FederatedTrustAuthority

A federated trust authority: M-of-K organizations, one aggregate key.

MemberOrg

One member organization of a federated trust authority.

MembershipChange

A membership change (join or leave) that must preserve the aggregate key so historical artifacts remain valid.

NonceCommitment

A commit-then-reveal nonce commitment preventing nonce bias.

NonceReveal

The reveal phase of a nonce commitment.

ProofOfPossession

Proof of possession contributed during DKG: the member’s signature over the session binding (authority id + nonce + its public key). Verifying every contribution against its claimed key is the rogue-key defense.

Enums

AbortReason

Why a ceremony aborted.

MembershipChangeKind

Join or leave.

Functions

attribute_dkg_failure

Attribute a failed DKG: find the first member whose contribution fails (identifiable abort), or attribute a timeout to the members that never contributed.