[seahorse/wip/userdocs: 16/244] help: Added draft for encryption-rsa.page

[Ekaterina Gerasimova <egerasimov src gnome org>]

commit 5dea4a2b818a129fc250ed592c8f750adff0575c
Author: Aruna Sankaranarayanan <arunasank src gnome org>
Date:   Mon Jun 17 21:59:42 2013 +0530

    help: Added draft for encryption-rsa.page

 help/C/encryption-rsa.page |   85 +++++++++++++++++++++++++++++++++++++++-----
 1 files changed, 76 insertions(+), 9 deletions(-)
---
diff --git a/help/C/encryption-rsa.page b/help/C/encryption-rsa.page
index dad6b15..6daffa4 100644
--- a/help/C/encryption-rsa.page
+++ b/help/C/encryption-rsa.page
@@ -4,23 +4,90 @@
   <info>
     <desc></desc>
     <link type="guide" xref="learn-about-keys" group="second"/>
+
     <revision version="0.1" date="2011-10-23" status="draft"/>
+    <revision pkgversion="3.9" date="2013-06-17" status="draft"/>
 
-    <credit type="author">
-      <name>Jim Campbell</name>
-      <email>jwcampbell gmail com</email>
+    <credit type="author copyright">
+      <name>Aruna Sankaranarayanan</name>
+      <email>aruna evam gmail com</email>
     </credit>
 
   </info>
 
   <title>What is RSA encryption?</title>
 
-  <!-- stefw: it would be difficult to recommend RSA vs. DSA to users
-     and help them understand why they would choose one over the other.
+  <p>The RSA <link xref="introduction">encryption algorithm</link> was
+  described by Rivest, Shamir and Adleman in 1977, hence the name of the
+  algorithm. RSA is quite popular because data encrypted using the RSA method
+  is virtually impossible to decrypt by anyone except the rightful recipient of
+  the data, if the key used is sufficiently large in size.</p>
+
+<section id="background">
+  <title>The math behind RSA</title>
+
+<!--aruna-Instead of explaining this section as the math behind the RSA,
+could we explain it as the logic behind the RSA by using the concept of random
+shapes?  So, we use two random shapes, and meld them to get a new shape, which
+acts as the public key and the one of the component shapes can be the private
+key that is known only to the user. This would also make adding pictures
+easier.-->
+
+  <p>When a number can be represented as the product of two numbers, the two
+  numbers are called its <em>factors</em>. A <em>prime number</em> is a number
+  whose only factors are 1 and the number itself.</p>
+
+  <note>
+    <p>3 is a prime number, since 3 can only be broken down as the product of
+    1 and 3. On the other hand, 6 is not a prime number since 6 can be broken
+    down as the products of 2 and 3, and, 1 and 6.</p>
+  </note>
+
+  <p>Say, that you are given two prime numbers, 17 and 19. It is quite easy to
+  calculate the product of these numbers by multiplying them. On the other
+  hand, if you were given just the product of these two numbers, 323, and asked
+  to find out the two numbers that have been multiplied, you would have quite a
+  task on hand since you would have to know at least one of the factors to
+  obtain the other. In other words, it is very difficult to obtain the 2
+  factors of a number, if both these factors are prime.</p>
+
+  <p>The RSA selects two very large prime numbers at random, and uses their
+  product to encrypt messages. This makes it very difficult to calculate the
+  two factors of the product, since both these factors are prime. Only a user
+  who is aware of one of the factors can decrypt the message and read it.</p>
+
+</section>
+
+<section id="steps">
+  <title>Steps of the RSA</title>
+
+  <p>Every user who wants to use the RSA algorithm has a key pair consisting
+  of a <em>Private key</em> and a <em>Public key</em>. The <em>Public key</em>
+  is available on several <link xref="key-servers-what-are-they">key
+  servers</link> and is visible to everyone. The <em>Private key</em> is only
+  visible to the owner of the key pair.</p>
+
+  <steps>
+    <title>How does RSA encryption work?</title>
+      <item>
+        <p>Say A and B want to communicate.</p>
+      </item>
+      <item>
+        <p>A encrypts the message to B with B's public key.</p>
+      </item>
+      <item>
+       <p>B receives the encrypted message and decrypts it with their private
+       key to view its contents.</p>
+      </item>
+      <item>
+       <p>B encrypts the reply to A with A's public key.</p>
+      </item>
+      <item>
+        <p>A receives the encrypted reply and decrypts it with their private
+       key to view its contents.</p>
+      </item>
+  </steps>
 
-     Unless you already have a plan for what will go here, it seems
-     this is a hard topic, but could include some information from
-     wikipedia for interest purposes only.
-  -->
+</section>
 
 </page>