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[2607:f8b0:4864:20::c2c]) by gmr-mx.google.com with ESMTPS id 6a1803df08f44-91ea68d5a9csi178076d6.6.2026.11.05.13.08.46 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Nov 2026 13:08:46 -0800 (PST) Received-SPF: pass (google.com: domain of connoravila@gmail.com designates 2607:f8b0:4864:20::c2c as permitted sender) client-ip=2607:f8b0:4864:20::c2c; Received: by mail-oo1-xc2c.google.com with SMTP id 006d021491bc7-703e2625ce6so3711eaf.0 for ; Thu, 05 Nov 2026 13:08:46 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1793912926; cv=none; d=google.com; s=arc-20260327; b=sBodzk3K/waWI+tef/g1Rg9AYO+hslQ/E1Atl1tLyT14ae6jT4A5N2y48jIfrJDswH /xvzyJBwbhsNjfDiNVfn9Xui+f4WXsiVFUqVquvtecq79y1mjeeYOBZV85h8q2p3/SPL mkVIhpSDqaKXTvdGTj6/ZSAU91ZH0KjMDq8Vcd0bHFe6qMsRM9NNbZBd9JFhWINSQXc9 v7ZbIxOsgsUZ6ExqAomOzEqOwHc3N7vLapa5cnQWsVcRYcschvJFU/rbMmYaUFpnHhh2 bQling2g7t8punHqJOyhFRyctGL4m6wsFU6P0dl9jRwYvME+Tad8zMxXoboj/Pis5Eue qnvQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20260327; h=to:subject:message-id:date:from:mime-version:dkim-signature; bh=1YTdOuZQTWrbNlHIo1zxcY98DhlKAtfxLEaeL/CynJA=; fh=VcGcg+Zjs9gw1uDcHbxsAILhBAcecnbJzZRdxgKVDIc=; b=f4Cot28e2FZv/ojPYGq2DVMsdTBUmqMoSUDe8R4GaBjBeeyNFA7swA7MX9LVk2PvtV cnkuo3kAAscPA5pyeHLcpz3hDSkxyqxlOYzZT8JAIjs+UMrWf9/VoJsHoV8/nuFKAR91 AOBKF6C3jPYHn3QX/Wi62BbpxPPbE2qMFi0u//HSdkQQPM2ROQOXXPLVQymIZEGAYc1m JD1XJkUZbo/hn7fWgWDD2tcf0to7KG/vNUNgSMOybgEY0texp16WaNXB7bSH+xDtiUR3 IHs6oFSvWIrxoaAKHFJvsCpLKP5CfZUEFHvfdHgA0zXuBfx3thK+b9IkqzCqswMZhk/F dtmA==; dara=google.com ARC-Authentication-Results: i=1; mx.google.com; arc=none X-Gm-Gg: AYBFou1Hgdfd9RRLg9dU+Z7rMVIaz42IavM4+tMRjVK4IQRIAOZlCSdXAyTjVV5BCVP TWmoKaKursYp/8yjv5QV52Dqw+2uTriWSlDaVFeigCYRktUUOBmcbLHirBwvnI1AhhtjoiwEtSD bl1Nmb+SgYWrFfuDBPDxaln8jzLT1G4ByFsH7qAOFHesCnNpYV61AYNJ82I2YfbevuJNBsDOSs/ O4Y61XRg78uAMvBfMOpjWGx6kiwh2nODHyF4FgNlwU+zbN7tbC68V4gjAPWBSe7JSvGbm/5pvIH HVK00fZ1leJUS4wIf+WM0bIS7k4H0+3lzYpG1nhccvcRMM3oXtOQUMN9tn4wp1MfD+PnhyZbHJQ pvhG44+Sap8Zrr+xPDsekGnZkcTtiA5Ga3fnyLjx79f1hOXbj41PHnLs7WEjw+/3AYdrHv22/c/ Dc6rOwlbIRn03l40SvJ+jaK9H3u8qaKIEAfOR1nE7eQAU5176FjAoVbKUK6GuscLkFUXV+7MAN4 rodpKfaBRrmL8uj74tWyNqHzL4Khik9Tzz5jMBugSVLwrwSdxuDzdEf2FplB1t452P2S1FX X-Received: by 2002:a05:6830:a19b:10b0:845:7cb:69b3 with SMTP id 46e09a7af769-85f1cb6426dmr694883a34.0.1793912925647; Thu, 05 Nov 2026 13:08:45 -0800 (PST) MIME-Version: 1.0 From: Connor Avila Date: Thu, 5 Nov 2026 16:08:33 -0500 X-Gm-Features: AclHuK_n2xvrsu3K9_o6k5U2aQlWpzeFYfupbuUP5QD9YcoMM5z5XCd8XGsreAc Message-ID: Subject: [bitcoindev] Draft BIPs: anti-exfil signing for BIP340 and ECDSA, with PSBT fields To: bitcoindev@googlegroups.com Content-Type: text/plain; charset="UTF-8" X-Original-Sender: connoravila@gmail.com X-Original-Authentication-Results: gmr-mx.google.com; dkim=pass header.i=@gmail.com header.s=20260707 header.b=clvUDn7k; arc=pass (i=1); spf=pass (google.com: domain of connoravila@gmail.com designates 2607:f8b0:4864:20::c2c as permitted sender) smtp.mailfrom=connoravila@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com; dara=pass header.i=@googlegroups.com Precedence: list Mailing-list: list bitcoindev@googlegroups.com; contact bitcoindev+owners@googlegroups.com List-ID: X-Google-Group-Id: 786775582512 List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , X-Spam-Score: -0.5 (/) Hi all, A signing device picks the nonce in every signature, so a compromised one can leak its seed through signatures that look normal. Anti-exfil fixes this by having the host contribute to each nonce and check the result. Devices already ship versions of it, but there's no agreed specification and no standard PSBT field for it. I've written two draft BIPs. One covers the protocol for BIP340 and ECDSA, including what a host does when a device fails. The other adds three PSBT input fields. The protocol follows Scheme 6 from Pieter Wuille's 2020 overview, with a sign-to-contract tweak. Sjors Provoost published an experimental draft in October for single-signer Taproot key-path signing, with implementations for HWI and several devices (https://github.com/Sjors/bips/pull/2). We've talked (or emailed rather), and he plans to align those implementations with this spec. With the BIPs are test vectors, a reference in Python, a C module for libsecp256k1, and a patch series adding it to Jade's `sign_psbt`, none of it run on a device yet. One script reruns most of the checks. No cryptographer has reviewed this and it hasn't been audited. The security argument starts with what it doesn't prove, and the evidence page lists what failed and what wasn't tested. I'm not a cryptographer, so corrections to the argument are much appreciated! Repository: https://github.com/AvilaLabs/anti-exfil Handbook: https://anti-exfil.avilalabs.org Connor Avila, Avila Labs -- You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/CAOuFX60em-d%3DJW%2BFmQe6G6mP58Gs6kpwuRwVLC5nwT8oO9HsXg%40mail.gmail.com.