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<concept id="GUID-5B112A34-1CBA-5B28-A941-27847FC1D30A" xml:lang="en"><title>Cryptography

overview</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-67CB0CE0-EFDA-4183-BB49-293580FFA0A5"><title>Purpose</title> <p>The

Cryptography module is the basis of the Symbian platform Security system.

The services provided by this module are used by the following components:

Certman (Certificate Management), Software Installation, Secure Communication

Protocols (for example, SSL, TLS, IPSEC), and WTLS. </p> <p>These services

include: </p> <ul>

<li id="GUID-4D104E90-FF18-5FF6-8D8F-806D31F9C81D"><p>symmetric encryption-decryption </p> </li>

<li id="GUID-62E013DC-85FD-5C7E-8F63-93C7F546F99E"><p>asymmetric encryption-decryption </p> </li>

<li id="GUID-716CAC33-4B7D-5F10-9F3A-CAFD6D42442F"><p>integrity checking and

signature verification </p> </li>

<li id="GUID-CE94FB08-21CE-51BD-9F2C-B857BC135902"><p>key exchange </p> </li>

<li id="GUID-72254184-BFDA-546A-97E9-0056F70ED602"><p>message digests </p> </li>

</ul> <p>The interface for the cryptographic services hides the implementation

details of particular algorithms. No detailed knowledge of the cryptographic

algorithms is needed to use the cryptographic services. </p> </section>

<section id="GUID-39C675AC-939A-4028-9016-27C66D869173"><title>Description</title> <p>The

Cryptography module encapsulates the following significant components: </p> <ul>

<li id="GUID-1B44BA90-11D8-5FD0-9554-4C7B788CEFF0"><p> <xref href="GUID-5B112A34-1CBA-5B28-A941-27847FC1D30A.dita#GUID-5B112A34-1CBA-5B28-A941-27847FC1D30A/GUID-59BBC450-1E19-58EA-8DD6-5F2D1EAB7D63">Cryptographic algorithms</xref>  </p> </li>

<li id="GUID-0FCB4381-6394-5A28-86FE-A1AAEC2ABEF5"><p> <xref href="GUID-5B112A34-1CBA-5B28-A941-27847FC1D30A.dita#GUID-5B112A34-1CBA-5B28-A941-27847FC1D30A/GUID-10F78AEF-4388-5A04-BD8D-A036171E3B82">Hash algorithms</xref>  </p> </li>

<li id="GUID-7CFF13A5-A55A-54F0-A3AD-1137E66D158B"><p> <xref href="GUID-5B112A34-1CBA-5B28-A941-27847FC1D30A.dita#GUID-5B112A34-1CBA-5B28-A941-27847FC1D30A/GUID-0630C916-ED45-520D-92CD-FE4F87A66D04">Random Number Generator (RNG)</xref>  </p> </li>

<li id="GUID-A42E03EF-DFC1-5646-8326-053E203A509C"><p> <xref href="GUID-5B112A34-1CBA-5B28-A941-27847FC1D30A.dita#GUID-5B112A34-1CBA-5B28-A941-27847FC1D30A/GUID-965474E9-6B4E-50C6-8F05-3381BBDC661A">Supporting APIs</xref>  </p> </li>

</ul> <p id="GUID-59BBC450-1E19-58EA-8DD6-5F2D1EAB7D63"><b>Cryptographic algorithms</b> </p> <p>These

algorithms allow data to be encrypted and decrypted. They include: </p> <ul>

<li id="GUID-D94D2386-B73D-5D07-A770-C73C81F80D5C"><p> <xref href="GUID-712DF59D-FAE1-592E-82A6-4E323676F5B8.dita">Symmetric

ciphers</xref> — algorithms that require communicating parties to hold a shared

secret. They are fast and used for the transmission of bulk data. </p> </li>

<li id="GUID-7425FC7D-BA33-5F0B-92A4-95876C790EBB"><p> <xref href="GUID-35E9F104-95F7-511F-B0C5-AB64BCA972D0.dita">Asymmetric

ciphers</xref> — algorithms which have two keys, one private to the keys'

owner and one which can be published. They are slow compared to symmetric

ciphers and are used to exchange a symmetric key before transmission of data

encrypted using that key. </p> </li>

</ul> <p>The classes implementing the symmetric and asymmetric ciphers are

provided in <filepath>cryptography.dll</filepath> (see <xref href="GUID-48DB00D7-3807-5B4B-B4CE-D8C05B42CA6D.dita">Cryptography

library</xref>). </p> <p id="GUID-10F78AEF-4388-5A04-BD8D-A036171E3B82"><b>Hash

algorithms</b> </p> <p>Hash algorithms compact a message down to a short series

of bytes from which it is impossible to regenerate the message. They are used

with an asymmetric cipher to generate signatures. </p> <p>The classes implementing

the hash algorithms are provided in <filepath>hash.dll</filepath>. </p> <p>Hash

algorithms are documented in the mainstream Symbian platform library. </p> <p id="GUID-0630C916-ED45-520D-92CD-FE4F87A66D04"><b>Random Number Generator

(RNG)</b> </p> <p>RNG is the basis for the cryptographic key generation. It

uses the RANROT algorithm seeded by random data available on the target hardware

(for example, free running counters available on ARM processors). </p> <p>The

Random number library is provided by <filepath>random.dll</filepath>. </p> <p>The

Random Number Generator API is documented in the mainstream Symbian OS Library. </p> <p id="GUID-965474E9-6B4E-50C6-8F05-3381BBDC661A"><b>Supporting APIs</b> </p> <ul>

<li id="GUID-1AFD7DEA-F5C8-56E4-AA71-359F893ED7C6"><p> <xref href="GUID-8119A243-2EF1-582A-BB94-BA2A18D02D2C.dita">Password

Based Encryption (PBE)</xref> — provides an API to encrypt and decrypt data

with a user-supplied password. </p> <p>The classes implementing PBE (for example,

for secure stream encryption) are provided in <filepath>pbe.dll</filepath>. </p> </li>

<li id="GUID-7A02B665-46BE-5DBB-9A8A-787120AA3D11"><p>Padding — is extra bits

concatenated with a key, password, or plaintext to make their length equal

to the block size. It defines the way blocks are filled with data when the

data to be encrypted is smaller than the block size. Padding is added at encryption

and checked on decryption. (See <xref href="GUID-712DF59D-FAE1-592E-82A6-4E323676F5B8.dita#GUID-712DF59D-FAE1-592E-82A6-4E323676F5B8/GUID-BDF6E245-AE19-55D6-89ED-BCBE0FCF006B">Block

and stream ciphers</xref> and <xref href="GUID-712DF59D-FAE1-592E-82A6-4E323676F5B8.dita#GUID-712DF59D-FAE1-592E-82A6-4E323676F5B8/GUID-A8F9A25F-B83E-5FE7-840F-4DCF246D3D96">CPadding

class relationships</xref>.) </p> <p>The Cryptography library supports <xref href="http://www.rsasecurity.com/rsalabs/node.asp?id=2125" scope="external">PKCS#1</xref> public

and private padding, and <xref href="http://www.rsasecurity.com/rsalabs/node.asp?id=2129" scope="external">PKCS#7</xref> style padding (see <xref href="ftp://ftp.rfc-editor.org/in-notes/rfc2315.txt" scope="external">RFC 2315</xref> section 10.3). </p> </li>

<li id="GUID-85009712-99DF-571D-88B1-6F2B86385762"><p> <xref href="GUID-C75726D3-E815-503D-8267-26DA27AD4787.dita">Big

integers</xref> — Implementation of arbitrarily large integers. </p> <p>Note

that although some methods are exported, the intent is that this library is

only for use by the Cryptography library and not by application code. </p> </li>

</ul> </section>

</conbody></concept>