Received: from che.mayfirst.org (che.mayfirst.org [IPv6:2001:470:1:116::7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by mx.ietf.org (Postfix) with ESMTPS id F1E6431 for ; Sat, 26 Sep 2026 02:21:44 +0000 (UTC) Authentication-Results: mx.ietf.org; dkim=pass header.d=fifthhorseman.net header.s=2019 header.b="f/xM93ly"; dkim=pass header.d=fifthhorseman.net header.s=2019rsa header.b=fagP7ebV; dmarc=pass (policy=none) header.from=fifthhorseman.net; spf=pass (mx.ietf.org: domain of dkg@fifthhorseman.net designates 2001:470:1:116::7 as permitted sender) smtp.mailfrom=dkg@fifthhorseman.net DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/simple; d=fifthhorseman.net; i=@fifthhorseman.net; q=dns/txt; s=2019; t=1790389297; h=from : to : cc : subject : in-reply-to : references : date : message-id : mime-version : content-type : from; bh=8LLwTm2JNrbnavzIiEKS9G3kHYadbqJNrASaXt8KP3M=; b=f/xM93lyD2zshSZPSiXgxAjMHPrgpPmqLasasJTUQr3kUvzSybNRQi6O6Ca5/XM623gyY Kr/tT9VFGxrZFuKCQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=fifthhorseman.net; i=@fifthhorseman.net; q=dns/txt; s=2019rsa; t=1790389297; h=from : to : cc : subject : in-reply-to : references : date : message-id : mime-version : content-type : from; bh=8LLwTm2JNrbnavzIiEKS9G3kHYadbqJNrASaXt8KP3M=; b=fagP7ebVqtBc2YdFqBMX+xHo04YKeDFFkeAa+aBjr7Aa1/ml4NAHMe3h8CtqtMD7OStpS HEnej2peTRDL46rwIcs5xO4Zzn9WBEpjDIU3QfMpTxd07j0lFZqrcIt6bjG5MVo6HDfOiue Rvk9B8kZoEWhW8mm+4hfOF5aNkINXJYreb/LSDzgRe5QUBHIzxxjPPrZ85fwf8Wf36KggQj Cml7mwqWVT1KLgY6hCPVqi9N8iUeB8A8CS0vlhl5vHgIlF+VRqsvwpcr+WLgYZ1MkRIWmx1 t/WQ6e1FRtbr5E8jLFLhTkelDfqCsw55udxSoquxdhrbpbk2G64pLXByueCA== Received: from fifthhorseman.net (lair.fifthhorseman.net [108.58.6.98]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature ECDSA (secp384r1) server-digest SHA384) (No client certificate requested) by che.mayfirst.org (Postfix) with ESMTPSA id C12FFF947; Fri, 25 Sep 2026 22:21:37 -0400 (EDT) Received: by fifthhorseman.net (Postfix, from userid 1000) id 0293613F647; Fri, 25 Sep 2026 17:06:21 -0400 (EDT) From: Daniel Kahn Gillmor To: Andrew Gallagher In-Reply-To: References: <87qzih40no.fsf@fifthhorseman.net> Autocrypt: addr=dkg@fifthhorseman.net; prefer-encrypt=mutual; keydata= xjMEZXEJyxYJKwYBBAHaRw8BAQdA5BpbW0bpl5qCng/RiqwhQINrplDMSS5JsO/YO+5Zi7HNFzxk a2dAZmlmdGhob3JzZW1hbi5uZXQ+wsARBBMWCgB5AwsJB0cUAAAAAAAeACBzYWx0QG5vdGF0aW9u cy5zZXF1b2lhLXBncC5vcmcS78JIJ7JbALqPiKEmva7/Pp16WwXWm9hbe5+B/UvnfwMVCggCmwEC HgEWIQTUdwQMcMIValwphUm7fpEBSV5r9wUCZadfkAUJBdnwRQAKCRC7fpEBSV5r9yNXAP442N0c zvisBroQSKKpo+OWm2JpnEJWoVheeJvoRtkBGQEA+edHylby8IGcNccq7rmM2rAXdofvrU1o6qow V+mmDwbOMwRnio4OFgkrBgEEAdpHDwEBB0Cw9HzJFl9lZn3UBaUqSMSgxjcdbd0MwNVcGZ8t8wdN EcLAvwQYFgoBMQWCZ4qODgkQu36RAUlea/dHFAAAAAAAHgAgc2FsdEBub3RhdGlvbnMuc2VxdW9p YS1wZ3Aub3JnhcN+tn41cAg01Kk56zcAfpdsh8j98PDe00mqKPfFvaYCmwK+oAQZFgoAbwWCZ4qO DgkQeAuFTtnCtJZHFAAAAAAAHgAgc2FsdEBub3RhdGlvbnMuc2VxdW9pYS1wZ3Aub3JnxsD8Sk5P Wgx8c/Zseo6OlCjyDC+Ogm17gTaUUIpxjWYWIQRjrBGOWy5dZsiKhad4C4VO2cK0lgAAdcQA/1RG dmrmvVxkBY2qNPjtERNwPga8Pf4IdlenrZ03NXM4AQC+TDHMpD7d5obEvUy8GYI3oThzYItPP8vv ChY+wbaIBRYhBNR3BAxwwhVqXCmFSbt+kQFJXmv3AAAKbgD+K1MZXnRKPdmA8DgNysyGRZY8cSVH HQcC7ZAAtV3i2+wA/0CyOYrbFYbyTRALgoERR07OHFoP+fJopQLMNQARVUELzjgEZ4qN+RIKKwYB BAGXVQEFAQEHQDTGlR+Qmn334e+bPqvojJVdFsiBf0leAAHP+ESqop8NAwEIB8LAAAQYFgoAcgWC Z4qN+QkQu36RAUlea/dHFAAAAAAAHgAgc2FsdEBub3RhdGlvbnMuc2VxdW9pYS1wZ3Aub3JnA5Lw b3wOOcoodImuVNw4PYq1U65FDC1Q2JMFIcJXqF0CmwwWIQTUdwQMcMIValwphUm7fpEBSV5r9wAA 6egA/j3QANSmogZ5VTF5KlI+BBye9ud/w9j7RLcCHU6u8AA1AQC3FGaNuv+uWOSa+eeEoI/aZrGd X5el8b/m6aXDDxDjDg== Date: Fri, 25 Sep 2026 17:06:20 -0400 Message-ID: <87jyo93usz.fsf@fifthhorseman.net> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="=-=-="; X-Spam-Level: * X-Spamd-Bar: + Message-ID-Hash: SCDAHBJYY6IGWUXWPH46LQ67ZAWBUGEW X-Message-ID-Hash: SCDAHBJYY6IGWUXWPH46LQ67ZAWBUGEW X-MailFrom: dkg@fifthhorseman.net X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; header-match-openpgp.ietf.org-0; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: openpgp@ietf.org X-Mailman-Version: 3.3.10 Precedence: list Subject: [openpgp] Re: implicit PSK key capabilities List-Id: "Ongoing discussion of OpenPGP issues." Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: --=-=-= Sig: t=p; b=iHUEARYKAB0WIQRjrBGOWy5dZsiKhad4C4VO2cK0lgUCarbiTAAKCRB4C4VO2cK0 lm4uAP9Xf5HumfLZMZ2saWbNRV0AUuT0zZ8uk+7HXwGaQiHzygD/WSCDIG6mhnzG oNmmfLUXHiUxGSxLQ+sNQq4WKcYATAI= From: Daniel Kahn Gillmor To: Andrew Gallagher Cc: openpgp@ietf.org Subject: Re: [openpgp] implicit PSK key capabilities In-Reply-To: References: <87qzih40no.fsf@fifthhorseman.net> Autocrypt: addr=dkg@fifthhorseman.net; prefer-encrypt=mutual; keydata= xjMEZXEJyxYJKwYBBAHaRw8BAQdA5BpbW0bpl5qCng/RiqwhQINrplDMSS5JsO/YO+5Zi7HNFzxk a2dAZmlmdGhob3JzZW1hbi5uZXQ+wsARBBMWCgB5AwsJB0cUAAAAAAAeACBzYWx0QG5vdGF0aW9u cy5zZXF1b2lhLXBncC5vcmcS78JIJ7JbALqPiKEmva7/Pp16WwXWm9hbe5+B/UvnfwMVCggCmwEC HgEWIQTUdwQMcMIValwphUm7fpEBSV5r9wUCZadfkAUJBdnwRQAKCRC7fpEBSV5r9yNXAP442N0c zvisBroQSKKpo+OWm2JpnEJWoVheeJvoRtkBGQEA+edHylby8IGcNccq7rmM2rAXdofvrU1o6qow V+mmDwbOMwRnio4OFgkrBgEEAdpHDwEBB0Cw9HzJFl9lZn3UBaUqSMSgxjcdbd0MwNVcGZ8t8wdN EcLAvwQYFgoBMQWCZ4qODgkQu36RAUlea/dHFAAAAAAAHgAgc2FsdEBub3RhdGlvbnMuc2VxdW9p YS1wZ3Aub3JnhcN+tn41cAg01Kk56zcAfpdsh8j98PDe00mqKPfFvaYCmwK+oAQZFgoAbwWCZ4qO DgkQeAuFTtnCtJZHFAAAAAAAHgAgc2FsdEBub3RhdGlvbnMuc2VxdW9pYS1wZ3Aub3JnxsD8Sk5P Wgx8c/Zseo6OlCjyDC+Ogm17gTaUUIpxjWYWIQRjrBGOWy5dZsiKhad4C4VO2cK0lgAAdcQA/1RG dmrmvVxkBY2qNPjtERNwPga8Pf4IdlenrZ03NXM4AQC+TDHMpD7d5obEvUy8GYI3oThzYItPP8vv ChY+wbaIBRYhBNR3BAxwwhVqXCmFSbt+kQFJXmv3AAAKbgD+K1MZXnRKPdmA8DgNysyGRZY8cSVH HQcC7ZAAtV3i2+wA/0CyOYrbFYbyTRALgoERR07OHFoP+fJopQLMNQARVUELzjgEZ4qN+RIKKwYB BAGXVQEFAQEHQDTGlR+Qmn334e+bPqvojJVdFsiBf0leAAHP+ESqop8NAwEIB8LAAAQYFgoAcgWC Z4qN+QkQu36RAUlea/dHFAAAAAAAHgAgc2FsdEBub3RhdGlvbnMuc2VxdW9pYS1wZ3Aub3JnA5Lw b3wOOcoodImuVNw4PYq1U65FDC1Q2JMFIcJXqF0CmwwWIQTUdwQMcMIValwphUm7fpEBSV5r9wAA 6egA/j3QANSmogZ5VTF5KlI+BBye9ud/w9j7RLcCHU6u8AA1AQC3FGaNuv+uWOSa+eeEoI/aZrGd X5el8b/m6aXDDxDjDg== Date: Fri, 25 Sep 2026 17:06:20 -0400 Message-ID: <87jyo93usz.fsf@fifthhorseman.net> Content-Type: text/plain; hp="clear" Content-Transfer-Encoding: quoted-printable On Fri 2026-09-25 20:43:18 +0100, Andrew Gallagher wrote: > On 25 Sep 2026, at 20:11, Daniel Kahn Gillmor wro= te: >>=20 >> I'm not sure i have a strong preference, but the latter approach >> (implicit capabilities) seemed easiest to write up. I've taken a >> crack at writing it down here > > I like the general direction here, but I think it would be simpler > (and more future proof) to invert the enumeration - in other words, > say that by default all capabilities are allowed, and just list any > exceptions or caveats. i guess i'm not sure what that would mean, really. no one is proposing any particular limit, but we also know that there is a general cryptographic consensus that using the same secret key in two distinct mechanisms runs the risk of being a footgun. I tried to avoid using exclusive language in the MR, and instead to list three use cases that have effective domain separation from each other as examples to give the reader a sense of how the mechanism could be used reliably. Actively encouraging people to use the same PSK anywhere seems risky given all the sharp edges that guidance is likely to expose. Anyway, i'm not wedded to the text i proposed, i just wanted to get the process moving. if anyone else wants to propose an alternative, i'd be happy to help review. --dkg --=-=-=--