Re: [Cfrg] Point format endian

"Dearlove, Christopher (UK)" <> Mon, 26 January 2015 11:08 UTC

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From: "Dearlove, Christopher (UK)" <>
To: Alyssa Rowan <>, "" <>
Thread-Topic: [Cfrg] Point format endian
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Date: Mon, 26 Jan 2015 11:08:50 +0000
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Subject: Re: [Cfrg] Point format endian
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Alyssa Rowan
> They are NOT bignums. As per TLS WG discussion, all new curves' wire formats are opaque octet strings.

They may be opaque to TLS, but here people actually need to manipulate them, and  the draft that's being discussed here actually uses the words little endian. That's a number.

Having opened this can of worms, it was to ask if this was a deliberate decision. It was. Open to people to agree or disagree, I just was a little surprised and wanted to check.

There are several layers to representation,  when not able to consider it as opaque. Mathematical entity, octet pattern (including endianness, but also things like rules for leading zeros) and framing (e.g. the 04 in SEC1 for uncompressed elliptic curve points in affine form). Here we need all of those (I'm not suggesting we don't have them).

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