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