Cipher suites supported by Corda

The set of signature schemes supported forms a part of the consensus rules for a Corda DLT network. Thus, it is important that implementations do not support pluggability of any crypto algorithms and do take measures to prevent algorithms supported by any underlying cryptography library from becoming accidentally accessible. Signing a transaction with an algorithm that is not a part of the base specification would result in a transaction being considered invalid by peer nodes and thus a loss of consensus occurring. The introduction of new algorithms over time will require a global upgrade of all nodes.

Corda has been designed to be cryptographically agile, in the sense that the available set of signature schemes is carefully selected based on various factors, such as provided security-level and cryptographic strength, compatibility with various HSM vendors, algorithm standardisation, variety of cryptographic primitives, business demand, option for post-quantum resistance, side channel security, efficiency and rigorous testing.

Before we present the pool of supported schemes it is useful to be familiar with Network certificates and API: Identity. An important design decision in Corda is its shared hierarchy between the TLS and Node Identity certificates.

Certificate hierarchy

A Corda network has 8 types of keys and a regular node requires 4 of them:

Network Keys

• The root network CA key
• The doorman CA key
• The network map key
• The service identity key(s) (per service, such as a notary cluster; it can be a Composite key)

Node Keys

• The node CA key(s) (one per node)
• The legal identity key(s) (one per node)
• The tls key(s) (per node)
• The confidential identity key(s) (per node)

We can visualise the certificate structure as follows (for a detailed description of cert-hierarchy, see Network certificates):

Supported cipher suites

Due to the shared certificate hierarchy, the following 4 key/certificate types: root network CA, doorman CA, node CA and tls should be compatible with the standard TLS 1.2 protocol. The latter is a requirement from the TLS certificate-path validator. It is highlighted that the rest of the keys can be any of the 5 supported cipher suites. For instance, network map is ECDSA NIST P-256 (secp256r1) in the Corda Network (CN) as it is well-supported by the underlying HSM device, but the default for dev-mode is Pure EdDSA (ed25519).

The following table presents the 5 signature schemes currently supported by Corda. The TLS column shows which of them are compatible with TLS 1.2, while the default scheme per key type is also shown in the last column.