kirandomtpm

Get random bytes from the TPM (tool + BCrypt RNG provider)

Description

In some cases, you need to get random bytes from your computer in another way than software (because you don't trust it).
Microsoft introduced with Windows 8 a RNG provider available for BCrypt, but removed it in Windows 10, and you can't force RNG to use TPM by an API (afyk).

I created a BCrypt RNG provider just for fun (and because it's only 3 kB).
It supports Windows 7, 8, 8.1, 10 and Server 2008R2, 2012, 2012R2, 2016, 2019, and TPM 1.2 and 2.0.
Its internal name is: Kiwi Random TPM Provider, and is defined in code as KIRANDOMTPM_PROV_NAME.

Of course, you need to have a supported TPM 1.2 or 2.0 installed (and recognized) on your system.

Usages

Install the provider

You must run commands as administrator.

Here for a x64 system:

C:\security\kirandomtpm\x64>copy /y kirandomtpmprov.dll %systemroot%\system32\kirandomtpmprov.dll
        1 fichier(s) copié(s).

C:\security\kirandomtpm\x64>copy /y ..\win32\kirandomtpmprov.dll %systemroot%\syswow64\kirandomtpmprov.dll
        1 fichier(s) copié(s).

C:\security\kirandomtpm\x64>tpm_getrandom install
Installing RNG provider `Kiwi Random TPM Provider`: OK

Note: you can also move files to system directories instead of copying them.

Generate random bytes

Test program

After the installation of the provider, you can use tpm_getrandom to get random bytes from the TPM:

C:\security\kirandomtpm\x64>tpm_getrandom 20
Retrieving 20 random bytes from `Kiwi Random TPM Provider` provider:

aa8df125e44cdc90c3460fa0a7882631f20557db

Note: if you did not register the provider, you can see the section 'Generate random bytes without registering the provider' below.

Your own code

I'm not you, but basicaly, it can be:

BCryptOpenAlgorithmProvider(&hAlgorithm, BCRYPT_RNG_ALGORITHM, KIRANDOMTPM_PROV_NAME, 0); // L"Kiwi Random TPM Provider"
BCryptGenRandom(hAlgorithm, buffer, sizeof(buffer), 0);
BCryptCloseAlgorithmProvider(hAlgorithm, 0);

You can find an example in tpm_getrandom.c file.

Remove the provider

You must run commands as administrator.

Here for a x64 system:

C:\security\kirandomtpm\x64>tpm_getrandom remove
Removing RNG provider `Kiwi Random TPM Provider`: OK

C:\security\kirandomtpm\x64>del %systemroot%\system32\kirandomtpmprov.dll

C:\security\kirandomtpm\x64>del %systemroot%\syswow64\kirandomtpmprov.dll

Generate random bytes without registering the provider

In some cases, you don't want (or can't) install the provider. No admin rights/only want to test the function. You can use the argument noreg just after the amount of bytes you want to generate on the command line.

C:\security\kirandomtpm\x64>tpm_getrandom 20 noreg
Retrieving 20 random bytes from `kirandomtpmprov.dll` library:

6a5071bf2523ec24b828133b31694e626756297b

List registered RNG provider(s)

C:\security\kirandomtpm\x64>tpm_getrandom list
User mode RNG algorithm(s):
 | Microsoft Primitive Provider
 | Kiwi Random TPM Provider

C:\security\kirandomtpm\x64>tpm_getrandom remove
Removing RNG provider `Kiwi Random TPM Provider`: OK

C:\security\kirandomtpm\x64>tpm_getrandom list
User mode RNG algorithm(s):
 | Microsoft Primitive Provider

Build

kirandomtpm is composed of two projects, one is the provider itself: kirandomtpmprov, the other one is a tool to test it: tpm_getrandom.

1. kirandomtpmprov is a library (DLL) and does not need to be linked against the C/C++ runtime. It only links ntdll, kernel32 and tbs.
2. tpm_getrandom is a console application (EXE) linked against the C/C++ runtime (msvcrt.dll or statically for other versions), kernel32, bcrypt and kirandomtpmprov (to use the application even when the provider is not registered).

Licence

CC BY 4.0 licence - https://creativecommons.org/licenses/by/4.0/

kirandomtpm needs coffee to be developed:

• PayPal: https://www.paypal.me/delpy/

Author

Benjamin DELPY gentilkiwi, you can contact me on Twitter ( @gentilkiwi ) or by mail ( benjamin [at] gentilkiwi.com )