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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-66BBA81D-2488-50B8-8822-43AAAA139DDE" xml:lang="en"><title>Overview |
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13 of random number generation</title><prolog><metadata><keywords/></metadata></prolog><conbody> |
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14 <section id="GUID-B5BD3E1A-AFBB-5526-B5EA-8FA51A17E596"><title>Overview</title> <p>The |
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15 purpose of the Random Number Generation API is the generation of cryptographically |
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16 strong random numbers. </p> <p>Several cryptographic applications rely upon |
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17 the randomness, unpredictability and irreproducibility of the random number |
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18 generator, such as: </p> <ul> |
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19 <li id="GUID-15685756-F94B-508C-A08C-8F0ECBC1A4AA"><p>one-time pads </p> </li> |
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20 <li id="GUID-7E3ED7CE-65C3-5E8B-9FF0-139763F3E54B"><p>key generation </p> </li> |
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21 <li id="GUID-0C65E7E4-A3F5-5EC4-9851-4A4E3090607B"><p>random nonces </p> </li> |
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22 <li id="GUID-3C16304A-CDA0-5F50-9D6C-D76C2D6EA586"><p>Initialization Vectors |
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23 (IVs) </p> </li> |
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24 <li id="GUID-59F195DE-94E7-56EE-9A7D-EAB5E401DF9A"><p>salts to be hashed with |
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25 passwords </p> </li> |
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26 <li id="GUID-96B7B9D1-AB0D-5A54-9C7F-771008F354C1"><p>unique parameters in |
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27 signing operations. </p> </li> |
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28 </ul> <p>The RNG uses the <xref href="http://www.agner.org/random/" scope="external">RANROT</xref> algorithm |
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29 seeded by random data available on the target hardware (for instance free |
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30 running counters available on ARM processors). <note><p>In order to be <b>fully</b> compliant |
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31 with DSS (Digital Signature Standard), applications using the cryptography |
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32 library must supply a <xref href="http://cr.yp.to/bib/2000/-dss.pdf" scope="external">FIPS-186-2</xref> CR |
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33 1 compliant random number generator. The library provides a mechanism for |
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34 using such a random number generator if required. </p></note></p> </section> |
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35 <section id="GUID-9350FD0E-7F09-5D82-BB91-EC1C8D740DBD"><title>The Random |
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36 Number Generation API</title> <p>The diagram below shows the main classes |
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37 used in the RNG, which are implemented in <filepath>random.dll</filepath>. |
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38 For information on each class see the Cryptography API Reference material. </p> <fig id="GUID-5326D881-8795-5803-8B82-EC02C0C40226"> |
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39 <title> The inheritance hierarchy for the RRandomSession and |
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40 CSystemRandom classes </title> |
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41 <image href="GUID-FD1BB5C6-A042-56C9-8F1F-B51BF9DF5389_d0e388684_href.png" placement="inline"/> |
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42 </fig><p><b>How to use TRandom</b> </p> <p> <codeph>TRandom</codeph> is a |
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43 cryptographically stong random number generator. Its declaration is: </p> <codeblock id="GUID-53D847C3-2A1A-51D8-93FA-F68EA2374551" xml:space="preserve">class TRandom |
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44 { |
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45 public: |
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46 IMPORT_C static void RandomL(TDes8& aDestination); |
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47 };</codeblock><note> The function <codeph>TRandom::Random()</codeph> which |
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48 panics rather than leaves when it cannot obtain a random number, is deprecated |
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49 from v9.1 onwards. </note> <p> <codeph>TRandom::RandomL()</codeph> generates |
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50 random bytes by first connecting to the random number generation server (using <codeph>RRandomSession</codeph>). |
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51 If the attempt to connect fails, <codeph>TRandom::RandomL()</codeph> leaves. </p> <p>The |
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52 server fills <codeph>aDestination</codeph> with randomly generated bytes up |
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53 to its current length (not its maximum length). If this fails, <codeph>TRandom::RandomL()</codeph> leaves. |
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54 If <codeph>aDestination</codeph> is 1024 or more bytes long, multiple calls |
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55 are made to the server. Finally, <codeph>TRandom</codeph> closes the session. </p> <p> <codeph>TRandom</codeph> can |
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56 be used like this: </p> <codeblock id="GUID-0472582C-D5BD-520D-848E-9989E8730851" xml:space="preserve">HBufC8* rand = HBufC8::NewLC(5); |
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57 TPtr8 pRand=rand->Des(); |
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58 pRand.SetLength(5); |
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59 TRandom::RandomL(pRand); |
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60 ... |
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61 CleanupStack::PopAndDestroy(rand);</codeblock> </section> |
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62 </conbody></concept> |