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Overview |
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Group |
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Quick Info
Windows NT
| Yes
| Win95
| OSR2
| Win32s
| No
| Import Library
| advapi32.lib
| Header File
| wincrypt.h
| Unicode
| WinNT
| Platform Notes
| None
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CryptGenRandom
[New - Windows NT]
[New - Windows 95, OEM Service Release 2]
The CryptGenRandom function fills a buffer with random bytes.
BOOL CRYPTFUNC CryptGenRandom(
HCRYPTPROV hProv,
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| DWORD dwLen,
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| BYTE *pbBuffer
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Parameters
hProv
[in] A handle to the application's CSP. An application obtains this handle
using the CryptAcquireContext function.
dwLen
[in] The number of bytes of random data to be generated.
pbBuffer
[in/out] The buffer the function is to copy the random data to. This buffer
must be at least dwLen bytes in length.
Optionally, the application can fill this buffer with data to use as an
auxiliary random seed. This is explained further in the "Remarks" section.
Remarks
The data produced by this function is "cryptographically random." It is far
more random than the data generated by the typical random number generator such
as the one shipped with your "C" compiler.
This function is often used to generate random initialization vectors and salt
values.
Seeding the Random Number Generator
All software random number generators work in fundamentally the same way. They
start with one truly random number, known as the "seed," and then use an
algorithm to generate a pseudo-random sequence of bits based on it. The most
difficult part of this process is to get a seed that is truly random. This is usually
based on user input latency, or the jitter from one or more hardware
components.
If your application has access to a good random source, then it can fill the pbBuffer buffer with some amount of random data before calling CryptGenRandom. The CSP will then use this data to further randomize its internal seed.
Failing to initialize the pbBuffer buffer before calling CryptGenRandom is acceptable.
Return Values
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero. To retrieve extended error
information, use the GetLastError function.
The following table lists the error codes most commonly returned by the GetLastError function. The error codes prefaced by "NTE" are generated by the particular
CSP you are using.
Error
| Description
| ERROR_INVALID_HANDLE
| One of the parameters specifies an invalid handle.
| ERROR_INVALID_PARAMETER
| One of the parameters contains an invalid value. This is most often an illegal
pointer.
| NTE_BAD_UID
| The hProv parameter does not contain a valid context handle.
| NTE_FAIL
| The function failed in some unexpected way.
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Example
See the "Example" section in the CryptSetKeyParam function.
See Also
CryptAcquireContext, CryptGenRandom, CryptSetKeyParam
Related Links
Software for Delphi and C++ Builder developers
Software for Visual Studio .NET developers
Software for Visual Basic 6 developers
Delphi Tips&Tricks
MegaDetailed.NET
TMS Scripter Studio Pro components for Delphi/C++Builder
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OLE Programmer's Reference (ole.hlp)
Microsoft Windows Pen API Programmer's Reference (penapi.hlp)
Microsoft Windows Sockets 2 Reference (sock2.hlp)
Microsoft Windows Telephony API (TAPI) Programmer's Reference (tapi.hlp)
Unix Manual Pages
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