X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=web%2Fmanual.md;h=fef8123a3ac13bf44f0551e53aece8d001ac7495;hp=e7bb4afc31ae21230fca77aabbea11c8b3dbc1af;hb=a826152ba51fd4813f715e5fa30e7d70407dc846;hpb=3af6411b482ed8db2243f3e11bb06cf3adba6936

diff --git a/web/manual.md b/web/manual.md
index e7bb4afc..fef8123a 100644
--- a/web/manual.md
+++ b/web/manual.md
@@ -447,9 +447,9 @@ User management
 para_server uses a challenge-response mechanism to authenticate
 requests from incoming connections, similar to ssh's public key
 authentication method. Authenticated connections are encrypted using
-a stream cipher, either RC4 or AES in integer counter mode.
+the AES stream cipher in integer counter mode.
 
-In this chapter we briefly describe RSA, RC4 and AES, and sketch the
+In this chapter we briefly describe RSA and AES, and sketch the
 [authentication handshake](#Client-server.authentication)
 between para_client and para_server. User management is discussed
 in the section on [the user_list file](#The.user_list.file).
@@ -457,33 +457,33 @@ These sections are all about communication between the client and the
 server. Connecting para_audiod is a different matter and is described
 in a [separate section](#Connecting.para_audiod).
 
-RSA, RC4, AES
--------------
+RSA and AES
+-----------
 
-RSA is an asymmetric block cipher which is used in many applications,
-including ssh and gpg. An RSA key consists in fact of two keys,
+A block cipher is a transformation which operates on fixed-length
+blocks. For symmetric block ciphers the transformation is determined
+by a single key for both encryption and decryption. For asymmetric
+block ciphers, on the other hand, the key consists of two parts,
 called the public key and the private key. A message can be encrypted
-with either key and only the counterpart of that key can decrypt
-the message. While RSA can be used for both signing and encrypting
-a message, paraslash uses RSA only for the latter purpose. The
-RSA public key encryption and signatures algorithms are defined in
-detail in RFC 2437.
-
-RC4 is a stream cipher, i.e. the input is XORed with a pseudo-random
-key stream to produce the output. Decryption uses the same function
-calls as encryption. While RC4 supports variable key lengths,
-paraslash uses a fixed length of 256 bits, which is considered a
-strong encryption by today's standards. Since the same key must never
-be used twice, a different, randomly-generated key is used for every
-new connection.
+with either key and only the counterpart of that key can decrypt the
+message. Asymmetric block ciphers can be used for both signing and
+encrypting a message.
+
+RSA is an asymmetric block cipher which is used in many applications,
+including ssh and gpg. The RSA public key encryption and signatures
+algorithms are defined in detail in RFC 2437. Paraslash relies on
+RSA for authentication.
+
+Stream ciphers XOR the input with a pseudo-random key stream to produce
+the output. Decryption uses the same function calls as encryption.
+Any block cipher can be turned into a stream cipher by generating the
+pseudo-random key stream by encrypting successive values of a counter
+(counter mode).
 
 AES, the advanced encryption standard, is a well-known symmetric block
-cipher, i.e. a transformation operating on fixed-length blocks which
-is determined by a single key for both encryption and decryption. Any
-block cipher can be turned into a stream cipher by generating
-a pseudo-random key stream by encrypting successive values of a
-counter. The AES_CTR128 stream cipher used in paraslash is obtained
-in this way from the AES block cipher with a 128 bit block size.
+cipher. Paraslash employs AES in counter mode as described above to
+encrypt communications. Since a stream cipher key must not be used
+twice, a random key is generated for every new connection.
 
 Client-server authentication
 ----------------------------
@@ -523,8 +523,8 @@ point on the communication is encrypted using the stream cipher with
 the session key known to both peers.
 
 paraslash relies on the quality of the pseudo-random bytes provided
-by the crypto library (openssl or libgcrypt), on the security of the
-implementation of the RSA, RC4 and AES crypto routines and on the
+by the crypto library (openssl or libgcrypt), on the security of
+the implementation of the RSA and AES crypto routines and on the
 infeasibility to invert the SHA1 function.
 
 Neither para_server or para_client create RSA keys on their