Key Management Interoperability Protocol

Participants in the OASIS 2017 interop at the 2017 RSA conference.

The Key Management Interoperability Protocol (KMIP) is an extensible communication protocol that defines message formats for the manipulation of cryptographic keys on a key management server. This facilitates data encryption by simplifying encryption key management. Keys may be created on a server and then retrieved, possibly wrapped by other keys. Both symmetric and asymmetric keys are supported, including the ability to sign certificates. KMIP also allows for clients to ask a server to encrypt or decrypt data, without needing direct access to the key.

The KMIP standard was first released in 2010. Clients and servers are commercially available from multiple vendors. The KMIP standard effort is governed by the OASIS standards body. Technical details can also be found on the official KMIP page and wiki.

Description

A KMIP server stores and controls Managed Objects such as symmetric and asymmetric keys, certificates, and user defined objects. Clients then use the protocol to access these objects subject to a security model that is implemented by the servers. Operations are provided to create, locate, retrieve and update managed objects.

Each managed object has an immutable Value such as a key block that contains a cryptographic key. They also contain mutable Attributes which can be used to store meta data about the keys. Some attributes are derived directly from the Value, such as the cryptographic algorithm and length of a key. Other attributes are defined in the specification for the management of objects such as the Application Specific Identifier which is usually derived from tape identification data. Additional identifiers can be defined by the server or client as need by the application.

Each object is identified by a unique and immutable object identifier that is generated by the server and is used to Get object values. Managed objects may also be given a number of mutable but globally unique Name attribute which can be used to Locate objects.

The types of managed objects that are managed by KMIP include

• Symmetric Keys.
• Public and Private Keys.
• Certificates and PGP Keys.
• Split Keys.
• Secret Data (passwords).
• Opaque Data for client and server defined extensions.

The operations provided by KMIP include

• Create—to create a new managed object such as a symmetric key, and return the identifier.
• Get—to retrieve an object's value given its unique identifier.
• Register—to store an externally generated key value.
• Add Attributes, Get Attributes, and Modify Attributes—to manipulate the attributes of a managed object.
• Locate—to retrieve a list of objects based on a conjunction of predicates.
• Re-Key—to create a new key that can replace an existing key.
• Create Key Pair—create asymmetric keys.
• (Re-)Certify—to certify a certificate.
• Split and Join n of m keys.
• Encrypt, Decrypt, MAC etc. -- cryptographic operations performed on the key management server.
• Export and Import keys to other KMIP servers.
• Operations to implement the NIST key life cycle.

Each key has a cryptographic state such as initial, Active, Deactive, Compromised. Operations are provided that manipulate the state in conformance with the NIST life cycle guidelines. The dates of each transformation are recorded, such as the date that a key was activated. Dates can be specified into the future so that keys automatically become unavailable for specified operations as they expire.

Message encoding

The KMIP protocol specifies several different types of encodings. The main one is a type-length-value encoding of messages, called TTLV (tag, type, length, value). Nested TTLV structures allow for encoding of complex, multi-operation messages in a single binary message.

There are also well defined XML and JSON encodings of the protocol for environments where binary is not appropriate. A very compact CBOR encoding is also provided for applications that require it.

All of these protocols are expected to be transmitted using TLS protocol in order to ensure integrity and security. However, it is also possible to register and retrieve keys that are wrapped (encrypted) using another key on the server, which provides and additional level of security.

KMIP profiles

KMIP also defines a set of profiles, which are subsets of the KMIP specification showing common usage for a particular context. A particular KMIP implementation is said to be conformant to a profile when it fulfills all the requirements set forth in a profile specification document. OASIS has put forth various profiles describing the requirements for compliance towards storage arrays and tape libraries, but any organization can create a profile.

Relationship to PKCS#11

PKCS#11 is an C API used to control a hardware security module. PKCS#11 provides cryptographic operations to encrypt and decrypt, as well as operations for simple key management. There is considerable amount of overlap between the PKCS#11 API and the KMIP protocol.

The two standards were originally developed independently. PKCS#11 was created by RSA Security, but the standard is now also governed by an OASIS technical committee. It is the stated objective of both the PKCS#11 and KMIP committees to align the standards where practical. For example, the PKCS#11 Sensitive and Extractable attributes are being added to KMIP version 1.4. Many of the same people are on the technical committees of both KMIP and PKCS#11.

KMIP 2.0 provides a standardized mechanism to transport PKCS#11 messages from clients to servers. This can be used to target different PKCS#11 implementations without the need to recompile the programs that use it.

KMIP implementations

The OASIS KMIP Technical Committee maintains a list of known KMIP implementations, which can be found on the OASIS website. As of March 2017, there are 28 implementations and 61 KMIP products in this list.

Interoperability between implementations

The KMIP standard is defined using a formal specification document, testcases, and profiles put forth by the OASIS KMIP technical committee. These documents are publicly available on the OASIS website.

Interop booths at the 2015 RSA conference. Each vendor interoperates with each other vendor.

Vendors demonstrate interoperability during a process organized by the OASIS KMIP technical committee in the months before each RSA security conference. These demonstrations are informally known as interops. KMIP interops have been held every year since 2010. The following chart shows the number of individual tests performed by each client and server vendor combination since 2012.

• 
  Individual interoperability tests performed by each server/client vendor combination since 2012
• 
  Results of 2017 OASIS KMIP interoperability testing

Full details of the result of the 2017 interop can be found on the OASIS website.

In 2014 the Storage Networking Industry Association (SNIA) announced a similar, but distinct KMIP testing platform. It is known as the SSIF KMIP Conformance Test Program. However, The SSIF KMIP Conformance Test Program was retired effective September 1, 2017, and according to the SNIA website, no new testing can be scheduled at this time.

Example

The following shows the XML encoding of a request to Locate a key named "MyKeyName" and return its value wrapped in a different key with ID "c6d14516-4d38-0644-b810-1913b9aef4da". (TTLV is a more common wire protocol, but XML is more human readable.)

<RequestMessage>
  <RequestHeader>
    <ProtocolVersion>
      <ProtocolVersionMajor type="Integer" value="3"/>
      <ProtocolVersionMinor type="Integer" value="0"/>
    </ProtocolVersion>
    <BatchErrorContinuationOption type="Enumeration" value="Stop"/>
    <BatchOrderOption type="Boolean" value="true"/>
  </RequestHeader>
  <BatchItem>
    <Operation type="Enumeration" value="Locate"/>
    <UniqueBatchItemID type="ByteString" value="1"/>
    <RequestPayload>
      <Attributes>
        <Name type="TextString" value="MyKeyName"/>
      </Attributes>
    </RequestPayload>
  </BatchItem>
  <BatchItem>
    <Operation type="Enumeration" value="Get"/>
    <UniqueBatchItemID type="ByteString" value="2"/>
    <RequestPayload>
      <KeyWrappingSpecification>
        <WrappingMethod type="Enumeration" value="Encrypt"/>
        <EncryptionKeyInformation>
          <UniqueIdentifier type="Integer" value="c6d14516-4d38-0644-b810-1913b9aef4da"/>
        </EncryptionKeyInformation>
      </KeyWrappingSpecification>
    </RequestPayload>
  </BatchItem>
</RequestMessage>

Version history

Summary of KMIP versions and features.

Version	Committee Draft	Main Features
1.0	Oct 2010	Initial version
1.1	Jan 2013
1.2	Jun 2014	Cryptographic Operations (Encrypt, Decrypt, Sign etc.). Introduction of Profiles, including Application Identifiers for tape libraries.
1.3	2015	Streaming Cryptographic Operations; Client Registration; Locate offset/Limit; Deprecate Templates; RNG queries;
1.4	2016	Better asynchronous operations; Import/export of keys to other servers; Support of PKCS #12; Standardized key wrapping; Certify Attributes; Client & Server Correlation Values; Descriptive Attributes; AEAD support; AES-XTS support; Create Secret Data; RSA PSS Support; Many extensions to Query.
2.0	2018	Removal of deprecated items; Efficient representation of attributes; Replacement of "x-" convention for custom attributes; Client Log operation; Date Time resolution 1 microsecond; Locate Destroyed; Better Error Handling and Result Reasons; ; Improved client Provisioning; new CSR object; Removal of Attribute Index; Support for tokenization; NIST Key Type attribute; Fixed length Unique Identifiers; Several new attributes and query extensions; Delegated Logins; Hashed Passwords; Multiple Unique ID placeholders; ReEncrypt support using data references; Set Attribute operation; PKCS #11 encapsulation.
2.1	2019	Ping; Process and query asynchronous requests; Standardize server side key rotation; Set and query attribute defaults; Set and query constraints on attributes;
3.0	2020	Add an explicit concept of KMIP users, modeled as System Objects; Lifecycle improvements to references to other objects using names as well as unique identifiers; Formalize object groups and hierarchies; Enhancements to Locate operation; Obliterate administrative operation; New CBOR encoding option.

See also

• Key management
• Key (cryptography)
• Encryption
• IEEE P1619 Security in Storage Working Group

External links

• "OASIS KMIP Technical Committee".

• "KMIP Implementations known to the KMIP TC".