var
    Prov: HCRYPTPROV;
    hKey: HCRYPTKEY;
    hXChagngeKey: HCRYPTKEY;
    //
    keyProvInfo: CRYPT_KEY_PROV_INFO;
    cc: TCryptContext;
    //
    encCertLen: DWORD;
    encCert: PByte;
    context: PCCERT_CONTEXT;
    encType: DWORD;
    DecodedCert: string;
    store: HCERTSTORE;
    n: PCCERT_CONTEXT;
    //
    CertInCont: TCert;
    CertBytes: string;
    pCertContext: PCCERT_CONTEXT;
    datalen: Integer;
    subjnamestring: pchar;

    //
    pb: PByte;
    pbSize: Cardinal;
    hPubKey: HCRYPTKEY;
    //

    EncryptAlgSize: DWORD;
    EncryptParamsSize: DWORD;
    EncryptAlgorithm: CRYPT_ALGORITHM_IDENTIFIER;
    EncryptParams: CRYPT_ENCRYPT_MESSAGE_PARA;
    RecipientCertArray: array of PCCERT_CONTEXT;
    cbContent: DWORD;
    cbEncryptedBlob: DWORD;
    pbEncryptedBlob: PByte;
    pbContent: PByte;

    Dummy: PByte;

    a: PChar;
    arCertContext: TMemoryStream;

    DT: TTime;
    i: Integer;

    DecryptParams: CRYPT_DECRYPT_MESSAGE_PARA;
    DecryptParamsSize: DWORD;

    FileContent: PChar;
    FileContentSize: Cardinal;

    DecryptSize: DWORD;
    DecryptedBlob: PByte;
    Certs: HCERTSTORE;

    PrivateKeyInfo: CERT_KEY_CONTEXT;

const
    ContName = 'Prism';
begin
    cc := TCryptContext.Create(PAnsiChar(ContName), CP_GR3410_94_PROV_A, PROV_GOST_94_DH, []);

    SetCurContainerPassword(cc.Provider, '12345678');
    CryptGetUserKey(cc.Provider, AT_KEYEXCHANGE, @hXChagngeKey);

    datalen := 0;
    if not CryptGetKeyParam(hXChagngeKey, KP_CERTIFICATE, nil, @datalen, 0) then
    begin
        MessageDlg('Error installing certificate in container: ' + IntToStr(GetLastError), mtError, [mbOK], 0);
        exit;
    end;

//Don't work with CryptDecryptMessage
//    SetLength(CertBytes, datalen);
//
//    if not CryptGetKeyParam(hXChagngeKey, KP_CERTIFICATE, PByte(PChar(CertBytes)), @datalen, 0) then
//    begin
//        MessageDlg('Error of certificate in container: ' + IntToStr(GetLastError), mtError, [mbOK], 0);
//        Exit;
//    end;
//
//    pCertContext := CertCreateCertificateContext(PKCS_7_ASN_ENCODING or X509_ASN_ENCODING, PByte(PChar(CertBytes)), datalen);
//
//    PrivateKeyInfo.cbSize := SizeOf(PrivateKeyInfo);
//    PrivateKeyInfo.hCryptProv := cc.Provider;
//    PrivateKeyInfo.dwKeySpec := AT_KEYEXCHANGE;
//    if not CertSetCertificateContextProperty(pCertContext, CERT_KEY_CONTEXT_PROP_ID, 0, @PrivateKeyInfo) then
//    begin
//        MessageDlg('Error in CERT_KEY_CONTEXT_PROP_ID: ' + IntToStr(GetLastError), mtError, [mbOK], 0);
//        Exit;
//    end;
//
//    datalen := 0;
//    if not CertGetCertificateContextProperty(pCertContext, CERT_KEY_CONTEXT_PROP_ID, nil, @datalen) then
//    begin
//        MessageDlg('Error in CertGetCertificateContextProperty: ' + IntToStr(GetLastError), mtError, [mbOK], 0);
//        Exit;
//    end;

    // Trying with CertStore 
    Certs := CertOpenSystemStore(0{cc.Provider}, 'MY');

    DecryptParamsSize := SizeOf(DecryptParams);
    ZeroMemory(@DecryptParams, DecryptParamsSize);

    DecryptParams.cbSize := DecryptParamsSize;
    DecryptParams.dwMsgAndCertEncodingType := PKCS_7_ASN_ENCODING or X509_ASN_ENCODING;
    DecryptParams.cCertStore := 1;
    DecryptParams.rghCertStore := Certs;//@pCertContext; 

    FileContent := PChar(LoadFromFile('c:\1.txt'));
    FileContentSize := GetFileSize('c:\1.txt');

    if not CryptDecryptMessage(@DecryptParams, PByte(FileContent), FileContentSize, nil, @DecryptSize, nil) then
    begin
        MessageDlg('Error decrypting information: ' + IntToStr(GetLastError), mtError, [mbOK], 0);
        Exit;
    end;

    GetMem(DecryptedBlob, DecryptSize);

    if not CryptDecryptMessage(@DecryptParams, PByte(FileContent), FileContentSize, DecryptedBlob, @DecryptSize, nil) then
    begin
        MessageDlg('Error decrypting information: ' + IntToStr(GetLastError), mtError, [mbOK], 0);
        Exit;
    end;

    memLog.Text := CopyStr(DecryptedBlob, DecryptSize); // PByte -> String

    arCertContext.Free;
    FreeMem(DecryptedBlob, DecryptSize);

    //
    CryptDestroyKey(hXChagngeKey);
    CertFreeCertificateContext(pCertContext);
    CryptReleaseContext(Prov, 0);
    cc.Free;
end;

    Certs := CertOpenSystemStore(cc.Provider, 'MY');

    pCertContext := nil;
    pCertContext := CertFindCertificateInStore(Certs, PKCS_7_ASN_ENCODING or X509_ASN_ENCODING, CERT_FIND_ANY, 0, nil, pCertContext);
    while (pCertContext <> nil) do
    begin
        PrivateKeyInfo.cbSize := SizeOf(PrivateKeyInfo);
        PrivateKeyInfo.hCryptProv := cc.Provider;
        PrivateKeyInfo.dwKeySpec := AT_KEYEXCHANGE;
        if not CertSetCertificateContextProperty(pCertContext, CERT_KEY_CONTEXT_PROP_ID, 0, @PrivateKeyInfo) then
        begin
            MessageDlg('Error in CERT_KEY_CONTEXT_PROP_ID: ' + IntToStr(GetLastError), mtError, [mbOK], 0);
            Exit;
        end;

        datalen := 0;
        if not CertGetCertificateContextProperty(pCertContext, CERT_KEY_CONTEXT_PROP_ID, nil, @datalen) then
        begin
            MessageDlg('Error in CertGetCertificateContextProperty: ' + IntToStr(GetLastError), mtError, [mbOK], 0);
            Exit;
        end;
        //
        pCertContext := CertFindCertificateInStore(Certs, PKCS_7_ASN_ENCODING or X509_ASN_ENCODING, CERT_FIND_ANY, 0, nil, pCertContext); 
    end;