2018-05-04 13:34:45 +00:00
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Supported cipher suites
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=======================
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.. contents::
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The set of signature schemes supported forms a part of the consensus rules for a Corda DLT network.
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Thus, it is important that implementations do not support pluggability of any crypto algorithms and do take measures
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to prevent algorithms supported by any underlying cryptography library from becoming accidentally accessible.
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Signing a transaction with an algorithm that is not a part of the base specification would result in a transaction
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being considered invalid by peer nodes and thus a loss of consensus occurring. The introduction of new algorithms
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over time will require a global upgrade of all nodes.
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Corda has been designed to be cryptographically agile, in the sense that the available set of signature schemes is
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carefully selected based on various factors, such as provided security-level and cryptographic strength, compatibility
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with various HSM vendors, algorithm standardisation, variety of cryptographic primitives, business demand, option for
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post-quantum resistance, side channel security, efficiency and rigorous testing.
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Before we present the pool of supported schemes it is useful to be familiar with :doc:`key-concepts-identity`,
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:doc:`permissioning` and :doc:`api-identity`. An important design decision in Corda is its shared hierarchy
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between the TLS and Node Identity certificates.
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Certificate hierarchy
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---------------------
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2018-05-09 14:19:35 +00:00
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2018-05-04 13:34:45 +00:00
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A Corda network has 8 types of keys and a regular node requires 4 of them:
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2018-05-24 13:30:36 +00:00
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**Network Keys**
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2018-05-04 13:34:45 +00:00
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* The **root network CA** key
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* The **doorman CA** key
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* The **network map** key
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2018-05-24 13:30:36 +00:00
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* The **service identity** key(s) (per service, such as a notary cluster; it can be a Composite key)
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**Node Keys**
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2018-05-04 13:34:45 +00:00
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* The **node CA** key(s) (one per node)
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* The **legal identity** key(s) (one per node)
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* The **tls** key(s) (per node)
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* The **confidential identity** key(s) (per node)
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We can visualise the certificate structure as follows (for a detailed description of cert-hierarchy,
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see :doc:`permissioning`):
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.. image:: resources/certificate_structure.png
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:scale: 55%
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:align: center
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Supported cipher suites
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-----------------------
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Due to the shared certificate hierarchy, the following 4 key/certificate types: **root network CA**, **doorman CA**,
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**node CA** and **tls** should be compatible with the standard TLS 1.2 protocol. The latter is a requirement from the
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TLS certificate-path validator. It is highlighted that the rest of the keys can be any of the 5 supported cipher suites.
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For instance, **network map** is ECDSA NIST P-256 (secp256r1) in the Corda Network (CN) as it is well-supported by the
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underlying HSM device, but the default for dev-mode is Pure EdDSA (ed25519).
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The following table presents the 5 signature schemes currently supported by Corda. The TLS column shows which of them
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2018-05-30 16:38:33 +00:00
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are compatible with TLS 1.2, while the default scheme per key type is also shown in the last column.
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2018-05-04 13:34:45 +00:00
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2018-05-09 14:19:35 +00:00
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+-------------------------+---------------------------------------------------------------+-----+-------------------------+
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| Cipher suite | Description | TLS | Default for |
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+=========================+===============================================================+=====+=========================+
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| | Pure EdDSA using the | | EdDSA represents the current state of the art in mainstream | NO | - node identity |
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| | ed25519 curve | | cryptography. It implements elliptic curve cryptography | | - confidential identity |
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| | and SHA-512 | | with deterministic signatures a fast implementation, | | - network map (dev) |
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| | | explained constants, side channel resistance and many other | | |
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| | | desirable characteristics. However, it is relatively new | | |
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| | | and not widely supported, for example, you can't use it in | | |
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| | | TLS yet (a draft RFC exists but is not standardised yet). | | |
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+-------------------------+---------------------------------------------------------------+-----+-------------------------+
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| | ECDSA using the | | This is the default choice for most systems that support | YES | - root network CA |
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| | NIST P-256 curve | | elliptic curve cryptography today and is recommended by | | - doorman CA |
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| | (secp256r1) | | NIST. It is also supported by the majority of the HSM | | - node CA |
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| | and SHA-256 | | vendors. | | - tls |
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| | | | - network map (CN) |
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+-------------------------+---------------------------------------------------------------+-----+-------------------------+
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| | ECDSA using the | | secp256k1 is the curve adopted by Bitcoin and as such there | NO | |
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| | Koblitz k1 curve | | is a wealth of infrastructure, code and advanced algorithms | | |
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| | (secp256k1) | | designed for use with it. This curve is standardised by | | |
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| | and SHA-256 | | NIST as part of the "Suite B" cryptographic algorithms and | | |
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| | | as such is more widely supported than ed25519. By | | |
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| | | supporting it we gain access to the ecosystem of advanced | | |
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| | | cryptographic techniques and devices pioneered by the | | |
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| | | Bitcoin community. | | |
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+-------------------------+---------------------------------------------------------------+-----+-------------------------+
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| | RSA (3072bit) PKCS#1 | | RSA is well supported by any sort of hardware or software | YES | |
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| | and SHA-256 | | as a signature algorithm no matter how old, for example, | | |
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| | | legacy HSMs will support this along with obsolete operating | | |
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| | | systems. RSA is using bigger keys than ECDSA and thus it is | | |
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| | | recommended for inclusion only for its backwards | | |
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| | | compatibility properties, and only for usage where legacy | | |
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| | | constraints or government regulation forbids the usage of | | |
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| | | more modern approaches. | | |
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+-------------------------+---------------------------------------------------------------+-----+-------------------------+
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| | SPHINCS-256 | | SPHINCS-256 is a post-quantum secure algorithm that relies | NO | |
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| | and SHA-512 | | only on hash functions. It is included as a hedge against | | |
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| | (experimental) | | the possibility of a malicious adversary obtaining a | | |
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| | | quantum computer capable of running Shor's algorithm in | | |
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| | | future. SPHINCS is based ultimately on a clever usage of | | |
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| | | Merkle hash trees. Hash functions are a very heavily | | |
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| | | studied and well understood area of cryptography. Thus, it | | |
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| | | is assumed that there is a much lower chance of | | |
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| | | breakthrough attacks on the underlying mathematical | | |
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| | | problems. However, SPHINCS uses relatively big public keys, | | |
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| | | it is slower and outputs bigger signatures than EdDSA, | | |
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| | | ECDSA and RSA algorithms. | | |
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+-------------------------+---------------------------------------------------------------+-----+-------------------------+
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