crypto/weakcrypto/docs/bigint.dox
author asimpson@symbian.org
Thu, 15 Oct 2009 17:48:29 +0100
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/**
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	@page bigint Big Integer
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	- @ref bigintWhat
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	- @ref bigintHow
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	@section bigintWhat What does the big integer library do?
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Some types of cryptography require the handling of finite arbitrary length
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integers.  This big integer library attempts to provide support for that
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requirement.
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It is capable of representing both negative and positive integers with an
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absolute value of less than 2<sup>32</sup>^(2<sup>32</sup>).
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	@section bigintHow How do I use the big integer library?
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There are four categories of exposed APIs:
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-# Creation of new integers given some other representation (descriptor, TUint,
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etc).
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@ref RInteger RInteger::NewL()
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-# Creation of new integers given some criteria (range, bitcount, prime). 
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@ref RInteger RInteger::NewRandomL(), RInteger::NewPrimeL()
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-# Exporting of previously created integers to descriptors. 
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@ref TInteger TInteger::BufferLC()
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-# Querying attributes about the size of a previously created integer. 
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@ref TInteger TInteger::BitCount(), TInteger::ByteCount(), TInteger::WordCount().
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The following code demostrates how to create an \c RInteger from a bitstring
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representation of a big integer.
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@code
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//This creates an RInteger from the following binary hexadecimal (base 16)
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//descriptor.  Note that the number is written overall in big endian (most
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//significant digit is first, least significant digit (ones digit) is last).  
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//P.S. The hexadecimal binary descriptor below is the base 16 representation
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//of the base 10 number 123456789012345678901234567890.
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RInteger integer = RInteger::NewL(_L8("18EE90FF6C373E0EE4E3F0AD2")); 
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CleanupStack::PushL(integer);
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//This next line converts the number stored by an RInteger into a binary, big
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//endian, hexadecimal descriptor.
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HBufC8* descriptor = integer.BufferLC();
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CleanupStack::Pop(descriptor);
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CleanupStack::PopAndDestroy(integer);
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//descriptor is the same as the original _L8 input value now.
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@endcode
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For more information on integers, including important memory management
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information and additional creation overloads, see \c RInteger @ref RInteger.
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*/
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