uses wcrypt2;

function CryptBuff(Buff: Pointer; lenBuff: Integer; const Password: AnsiString; ToCrypt: Boolean): Integer;
var
 hProv: HCRYPTPROV;
 hash: HCRYPTHASH;
 key: HCRYPTKEY;
 len: dWord;
begin

 CryptAcquireContext(@hProv, nil, nil, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
 CryptCreateHash(hProv, CALG_SHA, 0, 0, @hash);
 CryptHashData(hash, @Password[1], Length(Password), 0);
 CryptDeriveKey(hProv, CALG_RC4, hash, 0, @key);
 CryptDestroyHash(hash);
 len:= lenBuff;
 if ToCrypt then CryptEncrypt(key, 0, true, 0, Buff, @len, len)
            else CryptDecrypt(key, 0, true, 0, Buff, @len);
 result:= len;
 CryptReleaseContext(hProv, 0);
end;