Pas pour les debutants

svp j'ai besoin d 'explication de ce petit programme
if (!CryptAcquireContext(&m_hProv, NULL, MS_ENHANCED_PROV, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
{
m_hProv = NULL;
err = GetLastError();
USMTTRACE1(USMT_ERROR, "Not able to acquire crypt context. GetLastError returns 0x%X.", err);
return USMT_UNABLE_SETKEY;
}

if(!CryptCreateHash(m_hProv, CALG_SHA1, 0, 0, &m_hHash))
{
err = GetLastError();
USMTTRACE1(USMT_ERROR, "Not able create hash. GetLastError returns 0x%X.", err);
m_hHash = NULL;
return USMT_UNABLE_SETKEY;
}

if(!CryptHashData(m_hHash, key, size, 0))
{
err = GetLastError();
USMTTRACE1(USMT_ERROR, "Unable to create hash data. GetLastError returns 0x%X.", err);
return USMT_UNABLE_SETKEY;
}

if(!CryptDeriveKey(m_hProv, CALG_3DES, m_hHash, CRYPT_EXPORTABLE, &m_hKey))
{
err = GetLastError();
USMTTRACE1(USMT_ERROR, "Unable to drive key. GetLastError returns 0x%X.", err);
return USMT_UNABLE_SETKEY;

merci