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Home > Forums > Programmers > Development Tools > Embarcadero: Delphi > FAQs

Embarcadero: Delphi FAQ

How To

Use the Windows Crypto API for Pseudo-Random Data Generation by Glenn9999

faq102-7590

Posted: 5 Oct 12

For the unit this code uses, see FAQ102-7423: Use the Windows Crypto API to get a Hash of a file. .

The Windows cryptography oriented functions offers use of the CS-PRNG that is included in it. Calling it will produce a number of pseudo-random bytes which can be processed afterwards for whatever purpose is necessary in the program.

CODE

function GenerateRandom(Len:Cardinal): String;
// uses the MS CSPRNG to produce Len bytes into a string.  Returns the data in
// a string of len bytes.

var
  hProv: TCryptProv;
begin
  if not CryptAcquireContext(hProv, nil, MS_ENHANCED_PROV, PROV_RSA_FULL,
         CRYPT_VERIFYCONTEXT) then
    CryptAcquireContext(hProv, nil, MS_ENHANCED_PROV, PROV_RSA_FULL,
         CRYPT_NEWKEYSET + CRYPT_VERIFYCONTEXT);
  if hProv > 0 then
    try
      SetLength(Result, Len);
      CryptGenRandom(hProv, Len, @Result[1]);
    finally
      CryptReleaseContext(hProv, 0);
    end;
end;

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