doc: added/modernized text on AEAD ciphers [ci skip]

Signed-off-by: Nikos Mavrogiannopoulos <nmav@redhat.com>

1 files changed, 31 insertions, 18 deletions

diff --git a/doc/cha-intro-tls.texi b/doc/cha-intro-tls.texi
index a00db66037..d0fea82193 100644
--- a/doc/cha-intro-tls.texi
+++ b/doc/cha-intro-tls.texi
@@ -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.