X-Git-Url: https://www.wagner.pp.ru/gitweb/?a=blobdiff_plain;f=README.md;h=3ee1942e4c488bf186ad6d0633bb6bd009745b38;hb=556afe8dc2f0bcc32247ac99b649977dd3808d33;hp=5e4f302512d731fbf49ef9f0dc40cc4a649982b1;hpb=e6baf33e557c187eebd1eb1b777f213ceabc351e;p=oss%2Fctypescrypto.git

diff --git a/README.md b/README.md
index 5e4f302..3ee1942 100644
--- a/README.md
+++ b/README.md
@@ -28,7 +28,6 @@ Also, this extension takes some care of correctly converting textual
 information from ASN.1 structures into unicode.
 
 
-
 Digest calculation
 ------------------
 
@@ -45,6 +44,23 @@ ctypescrypto modules, so it would work with engine-provided digests.
 Additionally there is **DigestType** class which may be needed to
 construct CMS SignedData objects or add signatures to them.
 
+
+MAC calculation
+---------------
+
+Mac is Message Authentication Code - it is like keyed digest, which
+depends not only on message, but also on key, which should be used both
+when initially computing MAC and when verifying it. MACs can be viewed
+as "digital signatures with symmetric keys".
+
+Most common type of MAC is HMAC (i.e. hash-based MAC), described in 
+[RFC 2104](https://tools.ietf.org/html/rfc2104), but there are other,
+for instance [GOST 28147-89](https://tools.ietf.org/html/rfc5830) defines MAC based on symmetric cipher.
+Also GSM 0348 uses DES symmetric cipher as MAC. OpenSSL supports
+GOST mac via loadable engine module, but doesn't seem to support any
+non-HMAC MAC in the core. So, MAC is only test in the test suite which
+requires loadable engine.
+
 Symmetric ciphers
 -----------------
 
@@ -78,6 +94,19 @@ python big integer.
 X509 certificates
 -----------------
 
+Certificates are cryptographically signed documents, which tie together
+public key and some attributes of key owner (certificate subject).
+Certificates are signed by some trusted organizations called Certificate
+Authorities (one which have issued given certificate, is called
+certificate issuer). Your browser or operating system typically have
+predefined store of the trusted CA certificates (although nothing
+prevent you from running your own CA using openssl command line utility,
+and trust only it). 
+
+
+
+Certificates are described in [RFC 5280](http://tools.ietf.org/html/rfc5280)
+
 Module **ctypescrypto.x509** contains objects **X509** which represents
 certificate (and can be constructed from string, contained PEM
 or DER certificate) and object **X509Store** which is a store of trusted
@@ -103,6 +132,16 @@ some operations with CMS and certificate verification.
 CMS documents
 -------------
 
+CMS stands for Cryptographic Message Syntax. It is defined in the
+[RFC 5652](http://tools.ietf.org/html/rfc5652).
+CMS defines several types of documents. There is **SignedData**,
+which can be read by anyone, but is protected from authorized changes
+by digital signature of its author. There is **EnvelopedData** protected
+from unauthorized reading by cipher and allowed to be read only by
+owners of certain private keys, and there is **EncryptedData**, which
+are protected by symmetric cipher keys.
+
+
 There is basic factory function **CMS()**, which parses PEM or der
 representation of cryptographic message and generates appropriate
 object. There are **SignedData**, **EnvelopedData** and
@@ -170,6 +209,17 @@ Tests can be run using
 
 Test suite is fairly incomplete. Contributions are welcome.
 
+Note that you need properly installed OpenSSL library with set of CA
+certificates in the certs directory, otherwise default certstore test
+would fail.
+
+You also need gost engine to be available (check with 
+
+   openssl engine gost
+
+) otherwise mac test would crash with error. Unfortunately there is no
+non-HMAC MAC in the openssl core, so GOST MAC is only option.
+
 Possible future enhancements
 ----------------------------
 
@@ -178,5 +228,5 @@ Possible future enhancements
 3. OCSP ([RFC 6960](http://tools.ietf.org/html/rfc6960))request creation and response parsing
 4. Timestamping ([RFC 3161](http://tools.ietf.org/html/rfc3161))
 support.
-6. MAC support. Few people know that there is more MACs than just HMAC,
-and even fewer, that OpenSSL supports them.
+
+  vim: spelllang=en tw=72