Windows CE 3.0

This function fills a buffer with random bytes.

DWORD dwLen, 
BYTE *pbBuffer);


[in] Handle to the application's CSP. An application obtains this handle by using the CryptAcquireContext function.
[in] Specifies the number of bytes of random data to be generated.
[in/out] Pointer to the buffer that the function copies 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.

Return Values

TRUE indicates success. FALSE indicates failure. To get extended error information, call GetLastError. Common values for GetLastError are described in the following table. The error values prefaced by "NTE" are generated by the particular CSP you are using.

Value 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.


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 a 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.


See CryptSetKeyParam.


Runs On Versions Defined in Include Link to
Windows CE OS 2.10 and later Wincrypt.h   Cryptapi.lib
Note   This API is part of the complete Windows CE OS package as provided by Microsoft. The functionality of a particular platform is determined by the original equipment manufacturer (OEM) and some devices may not support this API.

See Also

CryptAcquireContext, CryptGenKey, CryptSetKeyParam

 Last updated on Tuesday, July 13, 2004

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