Commit e21b0af8 authored by Nikos Mavrogiannopoulos's avatar Nikos Mavrogiannopoulos
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doc: added/modernized text on AEAD ciphers [ci skip]


Signed-off-by: Nikos Mavrogiannopoulos's avatarNikos Mavrogiannopoulos <nmav@redhat.com>
parent 4ebc1e6c
Pipeline #9036508 skipped
......@@ -101,57 +101,70 @@ just after the handshake protocol has finished.
@cindex symmetric encryption algorithms
Confidentiality in the record layer is achieved by using symmetric
block encryption algorithms like @code{3DES}, @code{AES}
or stream algorithms like @code{ARCFOUR_128}.
Ciphers are encryption algorithms that use a single, secret,
key to encrypt and decrypt data. Block algorithms in CBC mode also provide
protection against statistical analysis of the data. Thus, if you're
using the @acronym{TLS} protocol, a random number of blocks will be
appended to data, to prevent eavesdroppers from guessing the actual
data size.
ciphers like @code{AES} or @code{CHACHA20}. Ciphers are encryption algorithms
that use a single, secret, key to encrypt and decrypt data. Early
versions of TLS separated between block and stream ciphers and had
message authentication plugged in to them by the protocol, though later
versions switched to using authenticated-encryption (AEAD) ciphers. The AEAD
ciphers are defined to combine encryption and authentication, and as such
they are not only more efficient, as the primitives used are designed to
interoperate nicely, but they are also known to interoperate in a secure
way.
The supported in @acronym{GnuTLS} ciphers and MAC algorithms are shown in @ref{tab:ciphers} and
@ref{tab:macs}.
@float Table,tab:ciphers
@multitable @columnfractions .30 .60
@headitem Algorithm @tab Description
@item AES-128-CBC, AES-256-CBC @tab
AES or RIJNDAEL is the block cipher algorithm that replaces the old
DES algorithm. It has 128 bits block size and is used in CBC mode.
@multitable @columnfractions .20 .20 .60
@headitem Algorithm @tab Type @tab Description
@item AES-128-GCM, AES-256-GCM @tab
AEAD @tab
This is the AES algorithm in the authenticated encryption GCM mode.
This mode combines message authentication and encryption and can
be extremely fast on CPUs that support hardware acceleration.
@item AES-128-CCM, AES-256-CCM @tab
AEAD @tab
This is the AES algorithm in the authenticated encryption CCM mode.
This mode combines message authentication and encryption and is
often used by systems without AES or GCM acceleration support.
@item AES-128-CCM-8, AES-256-CCM-8 @tab
AEAD @tab
This is the AES algorithm in the authenticated encryption CCM mode
with a truncated to 64-bit authentication tag. This mode is for
communication with restricted systems.
@item CAMELLIA-128-CBC, CAMELLIA-256-CBC @tab
This is an 128-bit block cipher developed by Mitsubishi and NTT. It
is one of the approved ciphers of the European NESSIE and Japanese
CRYPTREC projects.
@item CAMELLIA-128-GCM, CAMELLIA-256-GCM @tab
AEAD @tab
This is the CAMELLIA algorithm in the authenticated encryption GCM mode.
@item CHACHA20-POLY1305 @tab
AEAD @tab
CHACHA20-POLY1305 is an authenticated encryption algorithm based on CHACHA20 cipher and
POLY1305 MAC. CHACHA20 is a refinement of SALSA20 algorithm, an approved cipher by
the European ESTREAM project. POLY1305 is Wegman-Carter, one-time authenticator. The
combination provides a fast stream cipher suitable for systems where a hardware AES
accelerator is not available.
@item AES-128-CBC, AES-256-CBC @tab
Legacy (block) @tab
AES or RIJNDAEL is the block cipher algorithm that replaces the old
DES algorithm. It has 128 bits block size and is used in CBC mode.
@item CAMELLIA-128-CBC, CAMELLIA-256-CBC @tab
Legacy (block) @tab
This is an 128-bit block cipher developed by Mitsubishi and NTT. It
is one of the approved ciphers of the European NESSIE and Japanese
CRYPTREC projects.
@item 3DES-CBC @tab
Legacy (block) @tab
This is the DES block cipher algorithm used with triple
encryption (EDE). Has 64 bits block size and is used in CBC mode.
@item ARCFOUR-128 @tab
Legacy (stream) @tab
ARCFOUR-128 is a compatible algorithm with RSA's RC4 algorithm, which is considered to be a trade
secret. It is a considered to be broken, and is only used for compatibility
purposed. For this reason it is not enabled by default.
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