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74 lines
3.1 KiB
74 lines
3.1 KiB
Kernel Crypto API Interface Specification
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=========================================
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Introduction
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------------
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The kernel crypto API offers a rich set of cryptographic ciphers as well
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as other data transformation mechanisms and methods to invoke these.
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This document contains a description of the API and provides example
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code.
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To understand and properly use the kernel crypto API a brief explanation
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of its structure is given. Based on the architecture, the API can be
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separated into different components. Following the architecture
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specification, hints to developers of ciphers are provided. Pointers to
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the API function call documentation are given at the end.
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The kernel crypto API refers to all algorithms as "transformations".
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Therefore, a cipher handle variable usually has the name "tfm". Besides
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cryptographic operations, the kernel crypto API also knows compression
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transformations and handles them the same way as ciphers.
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The kernel crypto API serves the following entity types:
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- consumers requesting cryptographic services
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- data transformation implementations (typically ciphers) that can be
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called by consumers using the kernel crypto API
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This specification is intended for consumers of the kernel crypto API as
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well as for developers implementing ciphers. This API specification,
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however, does not discuss all API calls available to data transformation
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implementations (i.e. implementations of ciphers and other
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transformations (such as CRC or even compression algorithms) that can
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register with the kernel crypto API).
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Note: The terms "transformation" and cipher algorithm are used
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interchangeably.
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Terminology
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-----------
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The transformation implementation is an actual code or interface to
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hardware which implements a certain transformation with precisely
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defined behavior.
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The transformation object (TFM) is an instance of a transformation
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implementation. There can be multiple transformation objects associated
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with a single transformation implementation. Each of those
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transformation objects is held by a crypto API consumer or another
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transformation. Transformation object is allocated when a crypto API
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consumer requests a transformation implementation. The consumer is then
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provided with a structure, which contains a transformation object (TFM).
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The structure that contains transformation objects may also be referred
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to as a "cipher handle". Such a cipher handle is always subject to the
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following phases that are reflected in the API calls applicable to such
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a cipher handle:
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1. Initialization of a cipher handle.
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2. Execution of all intended cipher operations applicable for the handle
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where the cipher handle must be furnished to every API call.
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3. Destruction of a cipher handle.
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When using the initialization API calls, a cipher handle is created and
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returned to the consumer. Therefore, please refer to all initialization
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API calls that refer to the data structure type a consumer is expected
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to receive and subsequently to use. The initialization API calls have
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all the same naming conventions of crypto_alloc\*.
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The transformation context is private data associated with the
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transformation object.
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