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Re: [Cfrg] Elliptic Curves - curve form and coordinate systems (ends on March 12th)

Phillip Hallam-Baker <phill@hallambaker.com> Fri, 13 March 2015 12:43 UTC

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Date: Fri, 13 Mar 2015 08:43:06 -0400
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From: Phillip Hallam-Baker <phill@hallambaker.com>
To: Jakob Breier <Jakob.Breier@rwth-aachen.de>
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Subject: Re: [Cfrg] Elliptic Curves - curve form and coordinate systems (ends on March 12th)
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On Fri, Mar 13, 2015 at 8:18 AM, Jakob Breier <Jakob.Breier@rwth-aachen.de>
wrote:

> On 12.03.2015 20:19, Andrey Jivsov wrote:
>
>> * This proposal incurs 32 additional bytes of storage overhead for the
>> public key, for the total of 64 bytes (compare this with 260+ bytes for RSA
>> 2048).
>>
>
> The storage costs and transmission costs might be insignificant for
> machines, but I'd like to point out the human storage and transmission
> costs. Take a look at SSH keys for example. Compare how well you can
> visually parse several lines of keys in an authorized_keys file in these
> three formats:
>
> ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDRTSfbRohGanse3u4gnu8wOId85f5K
> KyEzo/l
> MabVM4J92n6r4NPgN46pQ3bTc8XzLO5zHXY/mPSwQru3Ks+
> 6Mcut7bDo0ohPcLcdIYGTbqXkfz3
> KNDbdXwPMcaPamLmugNnj9UK2cPe8Q7F9DGSLaQc1eiC0JS/
> Qm0gG3ULqX3DEDFQbLBzH326Lov
> 9gplu/U7D0bBiM7q7VQs32sz11L4KWY3RzUhuy6bQ7GGrkGvp78l7f+
> 56AvQNeIV8fDOWKNE73s
> Q3NybxWxQ771c5c+AZGYzkERlHWjxaxGA6V8ZUiE2VftHZ
> MY4k6z4DC9hiadxwmr85qWriC7RrT
> OjmN9 Alice-HomePc
>
> ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNT
> YAAAAIbmlzdHAyNTYAAABBBLB
> RUKndAEfMluniDolf8eJIdhh1l9C2iXKtnbvbM9vFbBMQ+
> l47i7wusn4G2RMYsFPbwlV4XQt4TT
> sEwkrcLss= Alice-HomePc
>
> ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICxtv8s7nwLqhkhryoY+w/
> u9ZrY7dr0ZPZhYuOS
> bxTIb Alice-HomePc
>

+1

The main reasons I am interested in ECC systems as a replacement for RSA
are:

* The short key size is more compatible with URI/fingerprint.
* New ways to deal with the problem of defective key generation[1].
* Better work factor safety margin (WF-128  rather than 112)
* Only feasible approach beyond 128 bit WF.

Performance is the easiest to measure but not the reason for making a
change.


[1] Comodo Group has pending IPR claims.

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