diff options
author | lloyd <[email protected]> | 2014-01-10 23:07:16 +0000 |
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committer | lloyd <[email protected]> | 2014-01-10 23:07:16 +0000 |
commit | ad6555f522ae16f6284e8dafa02f630b88bcf289 (patch) | |
tree | bd63c51dbeab75eb0f90c72589bc922141237056 /doc/manual/aead.rst | |
parent | 6894dca64c04936d07048c0e8cbf7e25858548c3 (diff) |
Split up docs into the reference manual, the website, and everything else.
Add `website` target to makefile.
Some progress towards fixing minimized builds.
TLS now hard requires ECDSA and GCM since otherwise a minimized build
has only insecure options.
Remove boost_thread dependency in command line tool
Diffstat (limited to 'doc/manual/aead.rst')
-rw-r--r-- | doc/manual/aead.rst | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/doc/manual/aead.rst b/doc/manual/aead.rst new file mode 100644 index 000000000..dbd06bbe1 --- /dev/null +++ b/doc/manual/aead.rst @@ -0,0 +1,89 @@ +AEAD Modes +======================================== + +.. versionadded:: 1.11.3 + +AEAD (Authenticated Encryption with Associated Data) modes provide message +encryption, message authentication, and the ability to authenticate additional +data that is not included in the ciphertext (such as a sequence number or +header). It is a subclass of :cpp:class:`Symmetric_Algorithm`. + +The AEAD interface can be used directly, or as part of the filter system by +using :cpp:class:`AEAD_Filter` (a subclass of :cpp:class:`Keyed_Filter` which +will be returned by :cpp:func:`get_cipher` if the named cipher is an AEAD mode). + +AEAD modes currently available include GCM, OCB, and EAX. All three use a +128-bit block cipher such as AES. + +.. cpp:class:: AEAD_Mode + + .. cpp:function:: void set_key(const SymmetricKey& key) + + Set the key + + .. cpp:function:: Key_Length_Specification key_spec() const + + Return the key length specification + + .. cpp:function:: void set_associated_data(const byte ad[], size_t ad_len) + + Set any associated data for this message. For maximum portability between + different modes, this must be called after :cpp:func:`set_key` and before + :cpp:func:`start`. + + If the associated data does not change, it is not necessary to call this + function more than once, even across multiple calls to :cpp:func:`start` + and :cpp:func:`finish`. + + .. cpp:function:: secure_vector<byte> start(const byte nonce[], size_t nonce_len) + + Start processing a message, using *nonce* as the unique per-message + value. + + Returns any initial data that should be emitted (for instance a header). + + .. cpp:function:: void update(secure_vector<byte>& buffer, size_t offset = 0) + + Continue processing a message. The *buffer* is an in/out parameter and + may be resized. In particular, some modes require that all input be + consumed before any output is produced; with these modes, *buffer* will + be returned empty. + + On input, the buffer must be sized in blocks of size + :cpp:func:`update_granularity`. For instance if the update granularity + was 64, then *buffer* could be 64, 128, 192, ... bytes. + + The first *offset* bytes of *buffer* will be ignored (this allows in + place processing of a buffer that contains an initial plaintext header) + + .. cpp:function:: void finish(secure_vector<byte>& buffer, size_t offset = 0) + + Complete processing a message with a final input of *buffer*, which is + treated the same as with :cpp:func:`update`. It must contain at least + :cpp:func:`final_minimum_size` bytes. + + Note that if you have the entire message in hand, calling finish without + ever calling update is both efficient and convenient. + + .. cpp:function:: size_t update_granularity() const + + The AEAD interface requires :cpp:func:`update` be called with blocks of + this size. + + .. cpp:function:: size_t final_minimum_size() const + + The AEAD interface requires :cpp:func:`finish` be called with at least + this many bytes (which may be zero, or greater than + :cpp:func:`update_granularity`) + + .. cpp:function:: bool valid_nonce_length(size_t nonce_len) const + + Returns true if *nonce_len* is a valid nonce length for this scheme. For + EAX and GCM, any length nonces are allowed. OCB allows any value between + 8 and 15 bytes. + + .. cpp:function:: size_t default_nonce_length() const + + Returns a reasonable length for the nonce, typically either 96 + bits, or the only supported length for modes which don't + support 96 bit nonces. |