<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
<!-- This component and the accompanying materials are made available under the terms of the License 
"Eclipse Public License v1.0" which accompanies this distribution, 
and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
<!-- Initial Contributors:
    Nokia Corporation - initial contribution.
Contributors: 
-->
<!DOCTYPE task
  PUBLIC "-//OASIS//DTD DITA Task//EN" "task.dtd">
<task id="GUID-F446E658-B717-5257-9C5C-442B07B19565" xml:lang="en"><title> Performing
Cryptographic Operations with Keys</title><abstract><p>You can use various types of algorithms (for example RSA sign,
DSA sign, Decrypt, DH key agreement, and so on) to perform cryptographic operations
with keys in the unified keystore. This section provides information on the
signing process. </p><p> The following steps explain the process of signing
keys by considering the example of an RSA signing operation:</p></abstract><prolog><metadata><keywords/></metadata></prolog><taskbody>
<steps id="GUID-E7265950-3F94-51A6-BD6E-E99A25152E0B">
<step id="GUID-98896CA9-D5F6-5FCD-92B8-627D701DD080"><cmd/>
<info>Create an object of type CUnifiedKeyStore using <xref href="GUID-818689D6-EB99-382E-A435-D9C6C5D464DE.dita#GUID-818689D6-EB99-382E-A435-D9C6C5D464DE/GUID-C7A96153-4179-3B3F-878D-1EAA64A98D39"><apiname>CUnifiedKeyStore::NewL()</apiname></xref> or <xref href="GUID-818689D6-EB99-382E-A435-D9C6C5D464DE.dita#GUID-818689D6-EB99-382E-A435-D9C6C5D464DE/GUID-217FBB3B-CEF5-36F2-A612-EDDA0982053C"><apiname>CUnifiedKeyStore::NewLC()</apiname></xref>. </info>
</step>
<step id="GUID-3CFD0F4D-5467-5FE5-9003-F16FDF6750B1"><cmd/>
<info>Initialise the member functions and keystore using the asynchronous
function <xref href="GUID-818689D6-EB99-382E-A435-D9C6C5D464DE.dita#GUID-818689D6-EB99-382E-A435-D9C6C5D464DE/GUID-6C5D732C-1FD1-3EF0-AC90-87690F891B8D"><apiname>CUnifiedKeyStore::Initialize()</apiname></xref>. </info>
</step>
<step id="GUID-73A277E5-45B8-5F87-B114-2004AE4DD4C5"><cmd/>
<info>List all the keys in the keystore and then retrieve the key to be signed
based on filter criteria. </info>
</step>
<step id="GUID-036E7985-FB51-52C5-BC27-4ADAD38E0923"><cmd>Invoke the <codeph>MKeyStore::Open()</codeph> function
for opening the key. This also enables the creation of an object capable of
performing the required signing operation. In the case of an RSA signing process,
the key is opened to create a <codeph>MRSASigner</codeph> object. </cmd>
<info> Note: The following table lists the objects created for different cryptographic
operations: </info>
<stepxmp><table id="GUID-0DE1BD27-AF6F-5CC1-8A9E-9D36380D4EBE">
<tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/>
<tbody>
<row>
<entry><p> <b>Operation</b>  </p> </entry>
<entry><p> <b>Object</b>  </p> </entry>
</row>
<row>
<entry><p>DSA Sign </p> </entry>
<entry><p> <codeph>MDSASigner</codeph>  </p> </entry>
</row>
<row>
<entry><p>Decrypt </p> </entry>
<entry><p> <codeph>MCTDecryptor</codeph>  </p> </entry>
</row>
<row>
<entry><p>DH Key Agreement </p> </entry>
<entry><p> <codeph>MCTDH</codeph>  </p> </entry>
</row>
</tbody>
</tgroup>
</table> </stepxmp>
</step>
<step id="GUID-D3E1854A-D798-5CB5-B528-AB5F672C2AC7"><cmd/>
<info>Use <codeph>MCTSigner::SignMessage()</codeph> or <codeph>MCTSigner::Sign()</codeph> to
perform the signing operation. </info>
</step>
</steps>
<result><p>The <codeph>CRSASignature</codeph> object contains the value of
the signing operation. </p> </result>
<example><p>The following code snippet shows RSA signing operation: </p><codeblock id="GUID-B7FA7CF8-38D6-5088-B51E-73AB04139997" xml:space="preserve">

//Create a file system session object
RFs iFs;
CleanupClosePushL(&amp;iFs);


//Initialise the keystore and member functions
CUnifiedKeyStore* keyStore = CUnifiedKeyStore::NewL(fs);
keyStore-&gt;Initialize(iStatus); //iStatus is a TRequestStatus object


...



// Create a filter to retrieve all keys from the store
TCTKeyAttributeFilter filter;
filter.iPolicyFilter = TCTKeyAttributeFilter:EAllKeys;



// Retrieve a list of all the keys from the key store
RPointerArray&lt;CCTKeyInfo&gt; iKeys; // This variable will contain the key to be signed
iKeyStore-&gt;List(iKeys,filter,iStatus);


...


// Retrieve the key based on the label you are looking for 
_LIT(Klabel,”keylabel”);
TInt keyCount = iKeys.Count();
for (i = 0; i &lt; keyCount; i++)
{
    CCTKeyInfo* keyInfo = iKeys[i];
    if (keyInfo-&gt;Label() == Klabel)
        {
            // Create a signer object for the key
            MRSASigner* iRSASigner
            // The signer object will be returned after the key has been opened for signing
            keyStore-&gt;Open(*keyInfo, iRSASigner, iStatus);
            break;
        }
}



// Perform the signing operation

// Define the data for signing

HBufC* dataToSign; 
dataToSign = HBufC::NewL(20);
_LIT(KTxtSign,"Data to be signed");
*dataToSign = KTxtSign; 


CRSASignature* iRSASignature;
// iRSASignature will contain the result after the completion
// of the following request

iRSASigner-&gt;SignMessage(*dataToSign, iRSASignature, iStatus);


...


// Retrieve the RSA signature value through the CRSASignature object 
TInt signature = iRSASignature-&gt;S();
</codeblock></example>
</taskbody><related-links>
<link href="GUID-C4389D60-2A8D-532D-9D92-E57B0CCD14CF.dita"><linktext>Unified Keystore</linktext>
</link>
</related-links></task>