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HCS‑16 Standard: Floras - AppNet Accounts

Status: Draft​

Version: 1.0​

Table of Contents​

  1. Authors
  2. Abstract
  3. Motivation
  4. Terminology
  5. Specification
    5.1. Prerequisites
    5.2. Flora Account Creation
    5.3. Flora Topics
    5.4. Profile Schema
    5.5. Message Protocol
    5.6. Lifecycle Flows
    5.7. Reference Implementation
  6. Security Considerations
  7. Versioning & Upgrades
  8. References
  9. Change Log

Authors​

Abstract​

HCS‑16 defines Flora accounts: multi-signature coordination accounts for decentralized AppNets on Hiero. A Flora extends the HCS‑15 Petal account concept to groups of 2+ independent accounts that jointly control assets, maintain shared state, and coordinate actions through consensus.

Key Components​

A Flora account consists of:

  1. Multisig Account – A Hiero account controlled by a threshold key (T-of-M) composed of member Petal public keys
  2. Three Mandatory HCS Topics:
    • Communication Topic (CTopic) – Coordination, governance, and member chat
    • Transaction Topic (TTopic) – Scheduled transaction proposals and approvals
    • State Topic (STopic) – State commitments and membership changes
  3. HCS‑11 Profile – Standardized metadata describing members, thresholds, topics, and policies

What This Standard Defines​

  • Canonical JSON schema for Flora metadata and messages
  • Complete lifecycle flows: creation, operation, membership changes, and dissolution
  • Security parameters for threshold selection, membership management, and data availability
  • Integration with HCS‑10 (messaging), HCS‑11 (profiles), HCS‑15 (Petals), and HCS‑17 (state attestation)

Motivation​

The Challenge​

Modern autonomous agents and decentralized applications require multi-party coordination primitives:

  • AI Agent Collectives – Multiple AI agents pooling resources for shared tasks
  • Escrow Wallets – Trusted intermediaries for marketplace transactions
  • Joint Ventures – Temporary business collaborations with shared treasury
  • Working Groups – Project-based teams with collective decision-making
  • Federated Services – Distributed systems requiring consensus

Current Limitations:

  • Manual multisig deployment is error-prone and expensive
  • Custom smart contracts require audit overhead and lack standardization
  • No native discovery mechanism for finding or joining multi-party accounts
  • Poor tooling integration across different implementations

The HCS‑16 Solution​

Flora accounts solve these challenges through four core principles:

1. Native Multisig​

Uses Hiero's built-in ThresholdKey directly - no Solidity bridges, no custom bytecode, minimal gas costs, reduced audit surface.

2. Structured Communication​

Three dedicated HCS topics provide clear separation of concerns:

  • CTopic – Human-readable coordination and governance
  • TTopic – Machine-parseable transaction proposals
  • STopic – Cryptographic state commitments

3. Standards Composability​

Flora members are HCS‑15 Petal accounts, so existing tooling works unchanged:

  • Profile resolution via HCS‑11
  • Messaging via HCS‑10
  • State attestation via HCS‑17

4. Discoverability & Negotiation​

Flora formation can leverage HCS‑10 channels, making multi-party coordination accessible to autonomous agents.

Terminology​

TermDefinition
FloraThe multisig account created under HCS‑16; a decentralized AppNet coordination account
PetalAn HCS‑15 account that shares a private key with its Base account
MemberA Petal account that participates in a Flora
Base AccountThe original Hiero account from which a Petal derives its key material
Threshold Key (T/M)A cryptographic key requiring T valid signatures out of M total member keys
CTopicCommunication Topic – Human/agent coordination, governance, and general messaging
TTopicTransaction Topic – Scheduled transaction proposals and approval messaging + tracking
STopicState Topic – State commitments, membership changes, and epoch transitions
Operator IDIdentifier format <signerAccountId>@<floraAccountId> used to attribute actions to specific members
EpochMonotonically increasing counter marking state transitions or membership changes

Specification​

Prerequisites​

Member Requirements​

A Flora MUST be composed of ≥ 2 Petal accounts, where each member:

  1. Has a valid HCS‑11 Petal profile including:

    • Profile type set appropriately (type 1 for AI agents, type 0 for personal)
    • Valid inboundTopicId for HCS‑10 communication
    • Discoverable profile reference in account memo (hcs-11:<resource>)
    • Base account reference if using HCS‑15 Petal pattern

  2. Uses ECDSA/secp256k1 key cryptography:

    • Required for future encryption capabilities
    • ED25519 keys are NOT supported (they lack encryption support)
    • Key must be accessible for signing Flora transactions

  3. Has sufficient HBAR balance for:

    • Topic message submissions (≈$0.0001 per message)
    • Transaction fees (account creation, topic creation)
    • Initial Flora funding contribution (if agreed upon by members)
    • Ongoing operational costs

Pre-Formation Considerations​

Before creating a Flora, prospective members SHOULD establish consensus on:

  1. Governance Parameters:

    • Threshold value T (signatures required for execution)
    • Total members M (must be ≥ 2)
    • Membership change policies (who can propose, voting requirements)
    • Transaction approval requirements (all, majority, threshold)

  2. Financial Terms:

    • Initial Flora account balance (recommended ≥ 20 HBAR)
    • Who funds the initial account creation
    • How operational costs are shared
    • Treasury management policies

  3. Communication Channels:

    • Optional pre-negotiation via HCS‑10 inbound topics
    • Discovery via HCS‑18 (when implemented)
    • Any additional external communication methods members make outside of Flora topics

  4. Topic Configuration:

    • Whether to implement HIP-991 custom fees on topics
    • Fee amounts (if applicable) for spam prevention
    • Transaction memo format preferences
    • Custom topic requirements beyond the three mandatory topics

Flora / AppNet Account Creation​

Flora creation follows a 6-step process that transforms independent Petal accounts into a coordinated multi-signature entity:

Step 1: Decentralized Discovery (Optional)​

Pre-formation negotiation can occur using HCS‑10 inbound topics for private negotiation:

  • Discovery Method: Use announce/propose/respond messages
  • Proposer Actions: References candidate announcements; candidates accept or reject
  • Output: Agreed upon memberAccounts, threshold (T of M), and funding expectations

Alternative: Members may negotiate off-chain via traditional communication channels or discover via HCS‑18 (when implemented).

Step 2: Key Assembly​

After members and details are finalized, construct the Flora's cryptographic foundation:

  1. Collect each member's public key (ECDSA/secp256k1)
  2. Create a KeyList containing all member public keys
  3. Set the threshold value (T signatures required)
  4. Verify all members can access their private keys for signing

Example (TypeScript):

const keyList = new KeyList();
keyList.setThreshold(threshold); // e.g., 2 for 2-of-3
for (const member of members) {
  keyList.add(member.pubKey);
}

Step 3: Flora Account Creation​

The proposer (or designated initiator) submits an AccountCreateTransaction:

Required Parameters:

  • key = KeyList(threshold, [PubKey1, PubKey2, ...]) – The T-of-M threshold key
  • maxAutomaticTokenAssociations = -1 – Recommended for flexibility
  • initialBalance = 20 HBAR – Funded by proposer (adjustable based on agreement)

Result: Hiero network returns the new Flora account ID (e.g., 0.0.777)

Step 4: Topic Creation​

Immediately after Flora account creation, create three TopicCreateTransactions:

Topic TypeEnumPurposeAdmin KeySubmit KeyMemo Format
Communication0Coordination & governanceT/M KeyList1/M KeyListhcs-16:0.0.777:0
Transaction1Scheduled transaction proposalsT/M KeyList1/M KeyListhcs-16:0.0.777:1
State2State commitments & membershipT/M KeyList1/M KeyListhcs-16:0.0.777:2

Key Configuration:

  • adminKey – Set to Flora's T/M threshold key (requires T signatures to modify topic)
  • submitKey – Set to 1/M threshold (allows any single member to post messages)

Why 1/M for submitKey? Enables any member to post messages without requiring threshold signatures for routine communication.

Step 5: Profile Publication​

Create and publish the Flora's HCS‑11 profile:

  1. Prepare Profile JSON with:

    • type: 3 (Flora profile type)
    • members array (account IDs of all Petal members)
    • threshold value
    • topics object (CTopic, TTopic, STopic IDs)
    • policies (optional governance rules)

  2. Upload Profile to:

    • HCS topic (via HCS‑1), or
    • IPFS/Arweave for persistent storage

  3. Set Flora Account Memo to reference the profile:

    hcs-11:<resourceLocator>

    Example: hcs-11:hcs://1/0.0.789103

Step 6: Member Acknowledgement​

Each member confirms Flora activation by posting to CTopic:

Acknowledgement Message:

{
  "p": "hcs-16",
  "op": "flora_created",
  "flora_account_id": "0.0.777",
  "topics": {
    "communication": "0.0.888",
    "transaction": "0.0.889",
    "state": "0.0.890"
  },
  "m": "Member acknowledgement"
}

Activation Criteria: Flora is considered Active when:

  • Super-majority (≥T) of members publish flora_created message to CTopic, OR
  • Members post initial state to STopic using HCS‑17 state_hash format

Transaction Memo: hcs-16:op:0:0

Internal Flora Topics​

Flora accounts utilize three mandatory HCS topics for structured coordination:

TopicPurposeRequiredTopic MemoTopic Type EnumMessage Protocol
Communication Topic (CTopic)Human / agent chat, off‑chain URL exchange, policy proposals, general communications. Future standards are planned to define task coordination.✅hcs-16:${floraId}:00HCS-16
Transaction Topic (TTopic)Broadcast of pre‑signed ScheduledTxn IDs, token association proposals, contract calls.✅hcs-16:${floraId}:11HCS-16
State Topic (STopic)Flora shared state that is needed for the Flora's purpose. State hash publications per HCS-17, membership attestations, epoch transitions. Required for valid Floras even if not utilized initially.✅hcs-16:${floraId}:22HCS-17

Topic Configuration Rules​

Admin Key: All three topics SHOULD share the exact same adminKey as the Flora's account key (T/M threshold). This ensures:

  • Topic modifications require consensus (T signatures)
  • Topics cannot be unilaterally changed by a single member
  • Consistent security model across Flora infrastructure

Submit Key: All topics SHOULD use 1/M keylist threshold to allow each member to submit independently. This enables:

  • Any member can post messages without waiting for others
  • Asynchronous communication and proposal submission
  • Efficient day-to-day operations

HIP-991 Custom Fees (Optional): Custom fees can be added to require HBAR or custom fungible token/NFT to submit messages. This:

  • Provides spam prevention mechanism
  • Creates economic incentives for thoughtful participation
  • Must be agreed upon before Flora creation

Topic Memo Format (Canonical)​

hcs-16:<flora_account_id>:<type>

Components:

  • hcs-16 – Protocol identifier
  • <flora_account_id> – The Flora account ID (e.g., 0.0.777)
  • <type> – Topic type enum: 0 = Communication, 1 = Transaction, 2 = State

Examples:

hcs-16:0.0.777:0  // Communication Topic for Flora 0.0.777
hcs-16:0.0.777:1  // Transaction Topic for Flora 0.0.777
hcs-16:0.0.777:2  // State Topic for Flora 0.0.777

Flora / AppNet Account Memo Structure​

Flora accounts use the HCS‑11 memo convention to reference their profile document. See HCS‑11 for the canonical grammar and examples.

Memo Format (delegated to HCS‑11):

hcs-11:<resource>

Where <resource> can be:

  • HCS HRL: hcs://<standard>/<topicId> (e.g., hcs://1/0.0.789103)
  • IPFS: ipfs://QmT5NvUtoM5nWFfrQdVrFtvGfKFmG7AHE8P34isapyhCxX
  • Arweave: ar://TQGxHPLpUcH7NG6rUYkzEnwD8_WqYQNPIoX5-0OoRXA
  • HTTPS: https://example.com/flora-profile.json

This approach provides flexibility in choosing the most appropriate storage mechanism for Flora metadata while maintaining a consistent reference pattern.

Profile Schema​

Flora accounts extend the canonical HCS‑11 profile schema. Refer to that standard for the authoritative definition of required fields such as type, members, threshold, and topics, as well as storage guidance.

Key Requirements:

  • Flora account memos MUST reference an HCS‑11-compliant profile document
  • Profile MUST set type: 3 (Flora profile type)
  • Flora account SHALL expose valid HCS‑10 inbound and outbound topics for coordination
  • Profile SHOULD include policies object for governance rules

Example Profile Snippet​

{
  "version": "1.0",
  "display_name": "🪷 AppNet #3",
  "type": 3,
  "members": [
    { "accountId": "0.0.1234" },
    { "accountId": "0.0.2345" },
    { "accountId": "0.0.3456" }
  ],
  "threshold": 2,
  "topics": {
    "communication": "0.0.481516",
    "transaction": "0.0.481517",
    "state": "0.0.481518",
    "custom": [
      {
        "name": "offChainHashes",
        "topicId": "0.0.792894",
        "description": "Used for attestation of offchain software"
      }
    ]
  },
  "policies": {
    "membershipChange": "2/3",
    "scheduleTxApproval": "all"
  }
}

Field Explanations:

  • members – Array of Petal account IDs participating in this Flora
  • threshold – Number of signatures required (T in T/M)
  • topics.communication – CTopic ID for coordination
  • topics.transaction – TTopic ID for scheduled transactions
  • topics.state – STopic ID for state commitments
  • topics.custom – Optional additional topics for specialized purposes
  • policies – Governance rules for operations (format is implementation-defined)

Message Protocol​

All Flora protocol messages follow a standardized envelope format and operation structure.

Protocol Operations​

Enumop (operation)DirectionPurposeProtocolRequired Keys
0flora_createdCTopicPublish final Flora account & topic IDs.HCS-16flora_account_id, topics
1transactionTTopicPropose a Scheduled Transaction for approval.HCS-16operator_id, schedule_id, data?, m?
2state_updateSTopicCommit state hash (simple format)HCS-16hash, epoch?
3flora_join_requestCTopicPost proxy of an external join request.HCS-16account_id, connection_request_id, connection_topic_id, connection_seq
4flora_join_voteCTopicMember vote on a join request.HCS-16account_id, approve, operator_id, connection_request_id, connection_seq
5flora_join_acceptedSTopicConfirmed membership change.HCS-16members, epoch
6state_hashSTopicCommit state hash (HCS-17 standardized)HCS-17state_hash, topics, account_id, epoch?

Notes:

  • State Publications: Flora STopics can use either HCS-16 state_update or HCS‑17 state_hash format
  • HCS-17 Benefits: The HCS-17 format provides standardized hash calculation, topic list verification, and composite state support
  • Protocol Mixing: STopic can receive both HCS-16 operations (2, 5) and HCS-17 operations (state_hash)
  • All operations follow their respective protocol's envelope structure

Envelope & Memos​

Canonical Message Envelope:

{ 
  "p": "hcs-16", 
  "op": "<op>", 
  "operator_id": "<signerAccountId>@<floraAccountId>", 
  "m": "optional" 
}

Field Descriptions:

  • p – Protocol identifier, always "hcs-16"
  • op – Operation type (see Operations table above)
  • operator_id – Identity of the acting member in format <signerAccountId>@<floraAccountId>
  • m – Optional human-readable memo for context

When executing transactions from the Flora account, it is RECOMMENDED to include a memo in this format for decentralized analytics and easier auditability of AppNet actions:

Memo Template:

hcs-16:op:<operationEnum>:<topicType>

Components:

  • hcs-16 – Protocol identifier
  • op – Indicates this is an operation memo
  • <operationEnum> – Numeric operation type (0-5, see table above)
  • <topicType> – Topic type enum: 0 = CTopic, 1 = TTopic, 2 = STopic

Examples:

hcs-16:op:0:0  // flora_created on CTopic
hcs-16:op:1:1  // transaction on TTopic
hcs-16:op:2:2  // state_update on STopic
hcs-16:op:3:0  // flora_join_request on CTopic
hcs-16:op:4:0  // flora_join_vote on CTopic
hcs-16:op:5:2  // flora_join_accepted on STopic
hcs-17:op:6:2  // state_hash on STopic

This standardized memo format enables:

  • Automated indexing and analytics of Flora operations
  • Network-wide monitoring of AppNet activity
  • Efficient filtering of Flora-related transactions
  • Debugging and audit trail reconstruction

Operation Methods​

Transaction (TTopic)​

Proposes a scheduled transaction that requires member approval before execution.

Message Shape:

{
  "p": "hcs-16",
  "op": "transaction",
  "operator_id": "0.0.123@0.0.777",
  "schedule_id": "0.0.999",
  "data": "Swap 1 HBAR for 10 XYZ",
  "m": "optional"
}

Fields:

FieldDescriptionTypeRequired
operator_idSigner account ID with Flora account ID combined by @: <signerAccountId>@<floraAccountId>stringYes
schedule_idHedera ScheduleId entity ID (e.g., 0.0.12345)stringYes
dataHuman description or helpful data or reference to data (HRL/URL)stringNo
mOptional memo for analytics/traceabilitystringNo

Transaction Memo: hcs-16:op:1:1

Usage Pattern:

  1. Member creates a ScheduleCreateTransaction on Hiero network for desired execution from Flora account
  2. Member posts transaction operation to TTopic with schedule ID of the new transaction
  3. Other members review the transaction details
  4. Members sign the scheduled transaction via ScheduleSignTransaction
  5. Transaction executes automatically when threshold (T) signatures reached

Flora Created (CTopic)​

Announces the successful creation of a Flora and its associated topics. Each member posts this message during Flora activation.

Message Shape:

{
  "p": "hcs-16",
  "op": "flora_created",
  "flora_account_id": "0.0.777",
  "topics": {
    "communication": "0.0.888",
    "transaction": "0.0.889",
    "state": "0.0.890"
  },
  "m": "optional"
}

Fields:

FieldDescriptionTypeRequired
flora_account_idNewly created Flora account IDstringYes
topicsThe three Flora topicsobjectYes
mOptional memostringNo

Transaction Memo: hcs-16:op:0:0

Purpose:

  • Confirms member participation in the Flora
  • Provides public record of Flora infrastructure
  • Establishes consensus on topic IDs

State Update (STopic)​

Commits a new state hash to the State Topic. Flora implementations can choose between HCS-16 simple format or HCS‑17 standardized format.

Option 1: HCS-17 State Hash Format​

Message Shape:

{
  "p": "hcs-17",
  "op": "state_hash",
  "state_hash": "<hex-encoded-sha384-hash>",
  "topics": ["0.0.888", "0.0.889", "0.0.890"],
  "account_id": "0.0.777",
  "epoch": 12,
  "m": "Flora composite state update"
}

Fields: See HCS‑17 Message Protocol for complete field definitions.

Transaction Memo: hcs-16:op:2:2

Benefits:

  • Standardized state hash computation per HCS-17 methodology
  • Inter-standard compatibility across HCS ecosystem
  • Includes topic list for verification
  • Built-in support for composite state hashes (Flora/Bloom)
  • Consistent epoch management
  • Deterministic calculation enables independent verification

Use When: You need standardized state verification, composite state aggregation, or interoperability with other HCS standards.

Option 2: HCS-16 State Update (Simple)​

Message Shape:

{
  "p": "hcs-16",
  "op": "state_update",
  "hash": "<stateHash>",
  "epoch": 12,
  "timestamp": "2025-09-15T12:00:00.000Z",
  "m": "optional"
}

Fields:

FieldDescriptionTypeRequired
hashState hash (application-defined format)stringYes
epochMonotonically increasing counternumberNo
timestampISO‑8601 timestampstringNo
mOptional memostringNo

Transaction Memo: hcs-16:op:2:2

Benefits:

  • Simpler format for straightforward use cases
  • Application-defined hash calculation
  • Fewer required fields

Use When: You have simple state requirements and don't need standardized hash calculation or composite state aggregation.

Join Request (CTopic)​

A proxy message posted to the CTopic by a Flora's intake automation or member, representing an external Petal's request to join the Flora.

Message Shape:

{
  "p": "hcs-16",
  "op": "flora_join_request",
  "account_id": "0.0.999",
  "connection_request_id": 51234,
  "connection_topic_id": "0.0.912345",
  "connection_seq": 27,
  "m": "This account reached out and requested to join"
}

Fields:

FieldDescriptionTypeRequired
account_idThe account requesting admission. Members use this to look up the candidate's HCS-11 profile.stringYes
connection_request_idSequence number of the HCS-10 connection_request on the Flora's inbound topic.numberYes
connection_topic_idThe HCS-10 connection topic ID for this join request.stringYes
connection_seqSequence number of the HCS-10 message on the connection topic containing the full join proposal.numberYes
mOptional purpose/memo.stringNo

Transaction Memo: hcs-16:op:3:0

Workflow Context:

  1. External Petal sends connection_request to Flora's HCS-10 inbound topic
  2. Intake automation (or member) detects the request
  3. Automation posts flora_join_request proxy to CTopic with references
  4. Members retrieve full proposal from connection topic using connection_seq
  5. Members vote using flora_join_vote operation

Join Vote (CTopic)​

Members cast votes on a flora_join_request. The vote references the specific request via HCS-10 sequence numbers to avoid ambiguity.

Message Shape:

{
  "p": "hcs-16",
  "op": "flora_join_vote",
  "account_id": "0.0.999",
  "approve": true,
  "operator_id": "0.0.123@0.0.777",
  "connection_request_id": 51234,
  "connection_seq": 27,
  "m": "optional"
}

Fields:

FieldDescriptionTypeRequired
account_idCandidate under vote.stringYes
approveBoolean decision (true = approve, false = reject).booleanYes
operator_idVoting member (<memberId>@<floraId>).stringYes
connection_request_idThe connection_request_id from the corresponding flora_join_request.numberYes
connection_seqThe connection_seq from the corresponding flora_join_request.numberYes
mOptional memo.stringNo

Transaction Memo: hcs-16:op:4:0

Voting Rules:

  • Each member casts one vote per join request
  • Vote is recorded on CTopic for transparency
  • Threshold (T) of approve: true votes required for acceptance
  • Members can change their vote by posting a new flora_join_vote message
  • Final acceptance requires executing KeyList update transaction

Join Accepted (STopic)​

Confirms a successful membership change by posting the updated member list and incrementing the epoch counter.

Message Shape:

{
  "p": "hcs-16",
  "op": "flora_join_accepted",
  "members": [
    "0.0.123",
    "0.0.456",
    "0.0.999"
  ],
  "epoch": 13,
  "m": "optional"
}

Fields:

FieldDescriptionTypeRequired
membersFull updated members liststring[]Yes
epochIncremented state counternumberYes
mOptional memostringNo

Transaction Memo: hcs-16:op:5:2

Purpose:

  • Provides canonical record of current membership
  • Enables state synchronization across members
  • Marks transition point in Flora history
  • Used for reconstructing Flora state from topic history

Protocol Message Examples​

Flora Activated — CTopic:

{
  "p": "hcs-16",
  "op": "flora_created",
  "flora_account_id": "0.0.777",
  "topics": {
    "communication": "0.0.888",
    "transaction": "0.0.889",
    "state": "0.0.890"
  }
}

Share a Scheduled Swap — TTopic:

{
  "p": "hcs-16",
  "op": "transaction",
  "operator_id": "0.0.123@0.0.777",
  "schedule_id": "0.0.999",
  "data": "Swap 1 HBAR for 10 XYZ"
}

Member Commit State Hash — STopic (HCS-17 format):

{
  "p": "hcs-17",
  "op": "state_hash",
  "state_hash": "a3f5b8c2d1e74f9a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a",
  "topics": ["0.0.888", "0.0.889", "0.0.890"],
  "account_id": "0.0.777",
  "epoch": 12
}

External Petal Join — Internal CTopic Message:

{
  "p": "hcs-16",
  "op": "flora_join_request",
  "account_id": "0.0.999",
  "connection_request_id": 51234,
  "connection_topic_id": "0.0.912345",
  "connection_seq": 27,
  "m": "Account 0.0.999 is requesting to join and would like to co‑fund 400 hbar to join"
}

Flora Creation — Sequence Diagram​

Lifecycle Flows​

JSON Envelope Conventions​

Every lifecycle message is valid UTF‑8 JSON and MUST include:

  • p:"hcs-16" — Protocol identifier
  • op — Operation type (see Operations table)
  • operator_id — Format: <signatureKeyAccountId>@<floraAccountId> for members; or <callerAccountId> for external join requests
  • m — Optional human‑readable memo

Additional Requirements:

  • All timestamps SHOULD use ISO-8601 format.
  • All topic IDs MUST use standard Hiero format (0.0.x)
  • JSON MUST be valid and parseable
  • String fields SHOULD be UTF-8 encoded
Example Lifecycle Messages​

Step 1: After Members Create the Flora

{
  "p": "hcs-16",
  "op": "flora_created",
  "flora_account_id": "0.0.777",
  "topics": {
    "communication": "0.0.888",
    "transaction": "0.0.889",
    "state": "0.0.890"
  }
}

Step 2: Initial State Commitment (HCS-17 format)

{
  "p": "hcs-17",
  "op": "state_hash",
  "state_hash": "48b6c9d2e1f8a3b5c7d9e2f4a6b8c0d2e4f6a8b0c2d4e6f8a0b2c4d6e8f0a2b4c6d8e0f2a4b6c8d0e2f4a6b8c0d2e4f6a8b0c2d4e6f8a0b2c4d6e8f0a2b4",
  "topics": ["0.0.888", "0.0.889", "0.0.890"],
  "account_id": "0.0.777",
  "epoch": 0
}

Creation (Happy Path)​

The standard Flora creation flow consists of three main phases:

1. Formation (HCS‑16)
Execute account & topic creation transactions on‑chain:

  • Create Flora multisig account with T/M threshold key
  • Create three mandatory topics (CTopic, TTopic, STopic)
  • Upload and reference HCS‑11 profile
  • Set Flora account memo to profile reference

2. Member Acknowledgement
Publish flora_created to CTopic:

  • Each member posts flora_created message
  • Message includes Flora account ID and topic IDs
  • Confirms member awareness and acceptance
  • Provides public record of Flora infrastructure

3. Initial State Publication
Publish initial state on STopic:

  • Prefer HCS‑17 state_hash format
  • Alternative: use HCS‑16 state_update operation
  • Establishes initial epoch (epoch 0 or 1)
  • Enables state synchronization across members

Flora Activation: Flora is considered ACTIVE when super-majority (≥T) of members complete Step 2 or 3.

Security Notes​

Key List Consistency
Before acceptance, members SHOULD verify:

  • The KeyList contains correct public keys for all members
  • Threshold value matches agreed-upon value
  • No unauthorized keys have been added
  • Transaction hash matches expected format

Resource Quota
The initiating member should supply enough ℏ for:

  • AccountCreateTransaction (≈0.10 HBAR)
  • Three TopicCreateTransactions (≈0.01 HBAR each)
  • Initial Flora account balance (recommended ≥20 HBAR)
  • Profile publication costs (if using HCS-1)

Sybil Resistance
Applications MAY impose additional requirements:

  • Allow-list of approved Petal accounts
  • Proof-of-work challenges
  • Required payments (HBAR or fungible tokens) for flora_join_request
  • Reputation scores or stake requirements
  • Rate limiting on join requests

Membership Change​

Add Member​

To add a new member to a Flora:

Step 1: Voting Phase (if required)

  • New candidate sends connection_request to Flora's or a members HCS-10 inbound topic
  • Intake automation posts flora_join_request to CTopic
  • Members cast votes using flora_join_vote operation
  • Track votes until threshold (≥T) reached

Step 2: KeyList Update Transaction

  • Any member posts transaction operation to TTopic with:
    • schedule_id referencing a ScheduleCreateTransaction
    • data field containing rationale (e.g., "Adding member 0.0.999 per vote")
  • The scheduled transaction MUST contain:
    • AccountUpdateTransaction for Flora account
    • Updated KeyList including new member's public key
    • Optionally updated threshold value (if agreed upon)

Step 3: Member Signing

  • Members sign the scheduled transaction via ScheduleSignTransaction
  • Execution occurs automatically when ≥T signatures collected
  • Network updates Flora account KeyList

Step 4: State Commitment

  • Member posts flora_join_accepted to STopic with:
    • Updated members array
    • Incremented epoch value
  • Update Flora profile (HCS-11) to reflect new membership

Transaction Memo: hcs-16:op:1:1 (for KeyList update transaction)

Remove Member​

Removing a member follows the same process as adding:

Key Differences:

  • KeyList update removes the member's public key
  • Threshold may need adjustment (ensure T ≤ remaining members)
  • flora_join_accepted SHOULD still be posted to mark the transition
  • Consider updating topic submit keys if member should lose access

Security Consideration: Removing a malicious member is itself a multisig transaction. For critical Floras, set membershipChange policy to require T+1 signatures where feasible.

Dissolution​

To permanently delete a Flora:

Pre-Dissolution Checklist:

  1. Asset Drainage – Transfer all HBAR and tokens out of Flora account
  2. Token Dissociation – Dissociate all tokens from Flora account
  3. Topic Cleanup – Optionally delete or transfer admin keys for topics
  4. Final State Commit – Post final state to STopic for historical record
  5. Member Coordination – Confirm all members agree on dissolution

Deletion Process:

Step 1: Coordinate on CTopic/TTopic

  • Members discuss and confirm dissolution plan
  • Agree on asset distribution
  • Execute all necessary cleanup transactions

Step 2: Post Deletion Transaction

  • Member posts transaction operation to TTopic with:
    • schedule_id referencing ScheduleCreateTransaction
    • data field: "Flora dissolution per member agreement"
  • Scheduled transaction contains AccountDeleteTransaction

Step 3: Member Signing

  • Members sign scheduled transaction
  • Execution occurs when signatures reach ≥T

Step 4: Network Execution

  • Hiero network deletes Flora account
  • Remaining balance (if any) transferred to beneficiary account
  • Flora account becomes permanently inaccessible

Read-Only State: If at any time active members fall below T, the Flora becomes Read-Only until membership is restored. This means:

  • No transactions can execute (insufficient signatures)
  • Topic messages can still be posted (1/M submit key)
  • Account balance remains but is inaccessible
  • Recovery requires adding new members (which itself requires ≥T signatures from existing members)

Important: Hiero requires all token associations and assets be cleared before account deletion. The deletion transaction will fail if:

  • Account holds any fungible tokens
  • Account holds any NFTs
  • Account has active token associations
  • Account has scheduled transactions pending

Reference Implementation​

Below is an abridged TypeScript example that assembles a 2‑of‑3 Flora. Error handling removed for brevity.

import {
  AccountCreateTransaction,
  KeyList,
  Hbar,
  TopicCreateTransaction,
  TopicId,
  Client,
  AccountId,
  PublicKey
} from "@hashgraph/sdk";

// Define member structure
type Member = { 
  accountId: AccountId; 
  pubKey: PublicKey;
};

// Configuration
const members: Member[] = await fetchMemberInfo(); // Retrieve from HCS-11 profiles
const threshold = 2; // 2-of-3 signatures required
const client = Client.forTestnet(); // Or mainnet

// Step 1a: Build Flora KeyList (T/M threshold)
const keyList = new KeyList();
keyList.setThreshold(threshold);
for (const m of members) {
  keyList.add(m.pubKey);
}

// Step 1b: Build Submit KeyList (1/M threshold for topics)
const submitKeyList = new KeyList();
submitKeyList.setThreshold(1);
for (const m of members) {
  submitKeyList.add(m.pubKey);
}

// Step 2: Create the Flora account
const floraReceipt = await new AccountCreateTransaction()
  .setKey(keyList)
  .setInitialBalance(new Hbar(20))
  .setMaxAutomaticTokenAssociations(-1)
  .execute(client)
  .then((tx) => tx.getReceipt(client));

const floraId = floraReceipt.accountId!;
console.log(`Flora account created: ${floraId}`);

// Step 3: Create the three mandatory topics
const [cTopicId, tTopicId, sTopicId] = await Promise.all([
  createTopic(`hcs-16:${floraId}:0`, keyList, submitKeyList), // CTopic
  createTopic(`hcs-16:${floraId}:1`, keyList, submitKeyList), // TTopic
  createTopic(`hcs-16:${floraId}:2`, keyList, submitKeyList), // STopic
]);

console.log(`Topics created:
  CTopic: ${cTopicId}
  TTopic: ${tTopicId}
  STopic: ${sTopicId}
`);

// Step 4: Create and upload Flora profile (HCS-11)
const profile = {
  version: "1.0",
  display_name: "Example Flora",
  type: 3,
  members: members.map(m => ({ accountId: m.accountId.toString() })),
  threshold: threshold,
  topics: {
    communication: cTopicId.toString(),
    transaction: tTopicId.toString(),
    state: sTopicId.toString()
  },
  policies: {
    membershipChange: "2/3",
    scheduleTxApproval: "threshold"
  }
};

// Upload profile using HCS-1 (implementation not shown)
const profileTopicId = await uploadProfileToHCS1(profile);

// Step 5: Update Flora account memo
await new AccountUpdateTransaction()
  .setAccountId(floraId)
  .setAccountMemo(`hcs-11:hcs://1/${profileTopicId}`)
  .execute(client)
  .then((tx) => tx.getReceipt(client));

console.log("Flora creation complete!");

// Helper function to create topics
async function createTopic(
  memo: string,
  adminKey: KeyList,
  submitKey: KeyList
): Promise<TopicId> {
  return new TopicCreateTransaction()
    .setAdminKey(adminKey)
    .setSubmitKey(submitKey)
    .setTopicMemo(memo)
    .execute(client)
    .then((tx) => tx.getReceipt(client))
    .then((receipt) => receipt.topicId!);
}

Additional Implementation Notes:

  1. Member Discovery: Use HCS-11 profile resolution to retrieve member public keys
  2. Key Management: Ensure all members securely store their private keys
  3. Error Handling: Production implementations should handle network failures, insufficient funds, and invalid keys
  4. Profile Storage: Choose appropriate storage mechanism (HCS-1, IPFS, Arweave) based on requirements
  5. Activation Monitoring: Implement listeners to track flora_created messages for activation confirmation

Security Considerations​

1. Key Reuse Risk​

Risk: Members typically reuse their Petal key inside Flora. Compromise of that private key affects all accounts using that key (Base account, Petal account, and all Flora memberships).

Mitigations:

  • USE CAUTION when managing private keys
  • Utilize hardware wallets (Ledger, Trezor) for key storage
  • Implement key rotation policies where possible
  • Consider using separate keys for high-value Floras
  • Monitor account activity for unauthorized transactions

Impact: Single key compromise can lead to:

  • Unauthorized Flora transactions (if attacker gains ≥T keys)
  • Theft of assets from Base and Petal accounts
  • Reputation damage if malicious actions are taken

2. Threshold Selection​

Choosing the right threshold (T) value is critical for balancing security and operational efficiency.

Recommendations:

Member Count (M)Recommended Threshold (T)Rationale
22Both members must agree (100% consensus)
32Allows one member to be offline
43Majority + 1, prevents 50/50 deadlock
5-7⌈⅔ M⌉Supermajority, balances liveness & safety
8+⌈⅔ M⌉Supermajority, ensures strong consensus

General Rule: For ≤ 4 members, T = M − 1 is RECOMMENDED. For 5+ members, T ≈ ⅔ M balances liveness with safety.

Considerations:

  • Too Low: Easier for malicious minority to execute unauthorized transactions
  • Too High: Increases risk of operational gridlock if members become unavailable
  • Liveness: Consider likelihood of members being offline
  • Safety: Consider trust level and potential for collusion

3. Membership Revocation​

Removing a malicious or compromised member is itself a multisig transaction requiring ≥T signatures.

Challenges:

  • Attacker with T−1 colluding members can block their own removal
  • Removal process can be slow if members are unresponsive
  • KeyList update requires coordination of honest members

Mitigations:

  • Set membershipChange policy to require T+1 signatures where feasible
  • Implement emergency procedures for rapid member removal
  • Maintain off-chain communication channels for crisis coordination
  • Consider time-locks on membership changes for additional security
  • Require higher threshold for removing founding members

Best Practice: Document clear procedures for handling compromised members, including:

  • Detection criteria (suspicious transactions, unresponsive members)
  • Emergency contact methods
  • Required evidence for removal votes
  • Asset protection measures during removal process

4. Data Availability​

Risk: Off‑chain storage (IPFS, Arweave, HTTPS) may become unavailable, making Flora metadata inaccessible.

Mitigations:

  • Prefer HCS‑1 for critical metadata (guaranteed availability on Hiero)
  • For IPFS: Pin files on multiple nodes (your own + pinning services)
  • For Arweave: Ensure proper funding for permanent storage
  • For HTTPS: Use reliable hosting with backups
  • Maintain local copies of all Flora metadata
  • Document alternative resolution paths in case of primary storage failure

Availability Guarantees by Storage Type:

Storage TypeAvailabilityPermanenceCostRecommendation
HCS-1Very HighPermanentLow✅ Recommended for critical data
IPFSMedium-HighVariableVery Low⚠️ Requires active pinning
ArweaveHighPermanentMedium✅ Good for large data
HTTPSVariableVariableLow❌ Not recommended

5. Topic Access Control​

Risk: Improper topic configuration can lead to unauthorized message submission or topic modification.

Best Practices:

  • Admin Key: Always set to Flora's T/M threshold key
  • Submit Key: Set to 1/M for routine operations, higher threshold for sensitive topics
  • Monitor: Implement automated monitoring for unauthorized topic messages
  • HIP-991 Fees: Consider adding custom fees to prevent spam
  • Key Updates: Require ≥T signatures for any topic key changes

6. Scheduled Transaction Security​

Risk: Malicious members could create scheduled transactions with misleading descriptions in the data field.

Mitigations:

  • Always verify scheduled transaction contents on Hiero network before signing
  • Don't rely solely on data field descriptions
  • Implement automated transaction analysis tools
  • Set expiration times on scheduled transactions (e.g., 7 days)
  • Require multiple members to verify high-value transactions
  • Use standardized transaction templates for common operations

Verification Checklist:

  • Schedule ID matches the one in TTopic message
  • Transaction type is as described
  • Amounts and recipients are correct
  • No unauthorized changes to Flora keys
  • Expiration time is reasonable
  • Transaction follows Flora policies

Profile Updates​

Flora profiles can be updated by:

  1. Uploading new profile JSON to storage
  2. Updating Flora account memo to reference new profile
  3. Posting state_update or similar notification to STopic

Backward Compatibility: New profiles SHOULD maintain compatibility with previous versions where possible. Add new fields rather than removing existing ones.

References​