[Gnuk-users] Ed25519 for signing broken?

[Jonathan Schleifer]

Am 09.02.2015 um 05:27 schrieb NIIBE Yutaka <gniibe at fsij.org>

> On 02/09/2015 05:03 AM, Jonathan Schleifer wrote:
>> So, even when not changing the PIN and keeping it at 123456, I still
>> get the bad signature error. It seems the problem happens only with
>> Ed25519. Is it possible the Ed25519 code on the Gnuk is not working
>> correctly as it is quite new?
> 
> It was pretty embarrassing bug of Gnuk.

Nothing to be embarrassed about. It's always these small bugs ;). And sometimes one looks for hours for a bug and then it's just a single character being wrong! :)

>    * src/openpgp.c (cmd_pso): Fix eddsa. Use GPG_KEY_FOR_SIGNING.
> 
> diff --git a/src/openpgp.c b/src/openpgp.c
> index e1d1203..5976255 100644
> --- a/src/openpgp.c
> +++ b/src/openpgp.c
> @@ -900,9 +900,9 @@ cmd_pso (void)
> 
> 	  res_APDU_size = EDDSA_SIGNATURE_LENGTH;
> 	  r = eddsa_sign_25519 (apdu.cmd_apdu_data, len, output,
> -				kd[GPG_KEY_FOR_AUTHENTICATION].data,
> -				kd[GPG_KEY_FOR_AUTHENTICATION].data+32,
> -				kd[GPG_KEY_FOR_AUTHENTICATION].pubkey);
> +				kd[GPG_KEY_FOR_SIGNING].data,
> +				kd[GPG_KEY_FOR_SIGNING].data+32,
> +				kd[GPG_KEY_FOR_SIGNING].pubkey);
> 	  memcpy (res_APDU, output, EDDSA_SIGNATURE_LENGTH);
> 	}
>     }

Thanks, I will try that later :).

In any case, would you be so kind to explain how exactly the keys are stored on the Gnuk? Having to store it with a secret derived from 123456, even if only temporary, worries me. Wouldn't it be possible to specify a PIN for the key when importing it? It currently asks for the admin PIN there, why not ask for a new PIN there, too?

Thanks,
Jonathan