From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id 5FB6262226 for ; Mon, 23 Nov 2020 09:56:01 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 51EC82596C for ; Mon, 23 Nov 2020 09:56:01 +0100 (CET) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [212.186.127.180]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS id E05892595F for ; Mon, 23 Nov 2020 09:56:00 +0100 (CET) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id B0ED143F0C for ; Mon, 23 Nov 2020 09:56:00 +0100 (CET) Date: Mon, 23 Nov 2020 09:55:50 +0100 (CET) From: Dietmar Maurer To: =?UTF-8?Q?Fabian_Gr=C3=BCnbichler?= , Proxmox Backup Server development discussion Message-ID: <278118200.83.1606121751476@webmail.proxmox.com> In-Reply-To: <1606118041.ki3x6lhgym.astroid@nora.none> References: <20201120163845.1225080-1-f.gruenbichler@proxmox.com> <20201120163845.1225080-10-f.gruenbichler@proxmox.com> <766783011.72.1606115268068@webmail.proxmox.com> <1606118041.ki3x6lhgym.astroid@nora.none> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Priority: 3 Importance: Normal X-Mailer: Open-Xchange Mailer v7.10.4-Rev13 X-Originating-Client: open-xchange-appsuite X-SPAM-LEVEL: Spam detection results: 0 AWL 0.115 Adjusted score from AWL reputation of From: address KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment RCVD_IN_DNSWL_MED -2.3 Sender listed at https://www.dnswl.org/, medium trust SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Subject: Re: [pbs-devel] [PATCH proxmox-backup 09/13] paperkey: add short key ID to subject X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 23 Nov 2020 08:56:01 -0000 > > I still don't get why we need a 32byte fingerprint - this is the same length as the key itself! > > the key (on disk) is 8 + 8 + 8 + 32 (key derivation) + 64 (encrypted key > data) + 8 + 8 (timestamps), totalling 136 bytes. serialized it's a bit > more, although there the fingerprint skews the numbers more heavily > (because I opted for a readable serialization, not one optimized for > size). even in-memory, the key is not 32-byte long, but 32+32+however > long the PKey struct from openssl is. For the record, the fingerprint is computed using 32 secret bytes (not more). Note: FINGERPRINT_INPUT is const + pub fn fingerprint(&self) -> Fingerprint { + Fingerprint { + bytes: self.compute_digest(&FINGERPRINT_INPUT) + } + } + pub fn compute_digest(&self, data: &[u8]) -> [u8; 32] { let mut hasher = openssl::sha::Sha256::new(); hasher.update(data); // this is const hasher.update(&self.id_key); // this is 32 bytes hasher.finish() } So the fingerprint has exactly the same size as the secret key. I really do not understand your arguments...