Create an HCS Topic

Hedera Consensus Service (HCS) topics are append-only public message logs with network-agreed timestamps. Anyone can read; writing is optionally gated by a submit key. An administrator key allows updating or deleting the topic.

Code

var receipt = await client.CreateTopicAsync(new CreateTopicParams
{
    Memo = "My Application Topic",
    Administrator = adminEndorsement,
    Submitter = submitEndorsement,
    RenewPeriod = TimeSpan.FromDays(90),
    RenewAccount = payerAccount
});
Console.WriteLine($"Topic ID: {receipt.Topic}");

What each parameter does

Parameter Description
Memo Required. Short description of the topic.
Administrator Optional. Key that can update or delete the topic. Without it the topic is immutable.
Submitter Optional. Key required to submit messages. Without it, anyone can submit.
RenewPeriod Auto-renewal interval (default 90 days).
RenewAccount Account paying renewal fees. If set, Administrator must also be set.

Public vs. gated topics

  • Public topic (no Submitter): any account can submit messages. Good for open audit logs.
  • Gated topic (with Submitter): only messages signed by the submit key are accepted. Good for application-controlled event streams.

See also