Re: [Cfrg] [TLS] Additional Elliptic Curves (Curve25519 etc) for TLS ECDH key agreement
Peter Gutmann <pgut001@cs.auckland.ac.nz> Mon, 13 January 2014 01:08 UTC
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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: "cfrg@irtf.org" <cfrg@irtf.org>
Thread-Topic: [Cfrg] [TLS] Additional Elliptic Curves (Curve25519 etc) for TLS ECDH key agreement
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Date: Mon, 13 Jan 2014 01:08:41 +0000
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Subject: Re: [Cfrg] [TLS] Additional Elliptic Curves (Curve25519 etc) for TLS ECDH key agreement
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Alyssa Rowan <akr@akr.io> writes: >EdDSA uses a hash to generate deterministic secret random exponents, to avoid >eating entropy when signing (like ECDSA does in its natural habitat). That >will need to be a big enough hash to cover the size we need: 512 bits covers >2^255 - 19, but to cover Curve3617 or E521, we're going to need a bigger boat. That assumes you need a single application of a hash function to do the job, which as several people have pointed out is going to bite you at some point when you run out of appropriately-sized hash functions. Why not use HKDF, RFC 5869, which works with any hash function you like? Peter.
- Re: [Cfrg] [TLS] Additional Elliptic Curves (Curv… Peter Gutmann
- Re: [Cfrg] [TLS] Additional Elliptic Curves (Curv… Jon Callas