On Canton you cannot see who else was in a transaction

How Canton Splits and Encrypts Each Transaction

Most blockchains hand every participant a copy of every transaction. @CantonNetwork takes a different approach. All transaction data transferred between participant nodes is end-to-end encrypted and shared only on a strict need-to-know basis. The mechanism that makes this work is sub-transaction privacy: when a transaction involves multiple parties, it is split into views based on stakeholder relationships, each view is encrypted to its respective recipients, and participants confirm based on their view alone.

In a typical securities settlement, the practical effect is clear-cut. The bank sees the cash leg; the registrar sees the asset leg. For the parts of a transaction a participant is not entitled to, they see neither any transaction payload nor metadata such as which parties were involved. Rather than replicating the entire ledger on every node, Canton's applications segregate data so that stakeholders only see the details they need.

What the Synchronizer Can and Cannot See

The component that orders these encrypted messages is the synchronizer, and its limitations are just as important as its capabilities. Unlike traditional public blockchains where transaction data is public, Canton's synchronizer cannot decrypt the transaction payloads. Messages are always encrypted end-to-end between the relevant participants, and the synchronizer sees only encrypted envelopes and their metadata for routing and ordering.

Canton's own technical documentation puts it plainly: the synchronizer does not see any of the data passing between validators. It just routes and orders encrypted packages, which it cannot decrypt. It is a bit like a post office dealing with sealed envelopes which it cannot open.

That said, routing still requires some information. Synchronizer components route messages between connected nodes, establish transaction ordering, and confirm transaction commits. In Canton's architecture, a synchronizer consists of a sequencer and a mediator. A mediator node within the synchronizer aggregates stakeholder confirmations and coordinates the commit decision, meaning that while content remains hidden, the infrastructure still handles the envelope-level data needed to keep the network coordinated.

The result is a model designed for regulated finance, where confidentiality between counterparties is not optional. Canton enables selective visibility and the ability to program privacy at the smart contract level, ensuring parties only see what they need to see, while ensuring synchronization of state across the entire network.

Sources:
Canton Network Docs: Privacy Model Explained
Canton Network Docs: Synchronizer Overview
Canton Network Blog: How Canton Delivers Institutional-Grade Privacy