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Re: Streaming - [Re: CryptoOperation and its life cycle]

From: Wan-Teh Chang <wtc@google.com>
Date: Fri, 14 Dec 2012 05:58:56 -0800
Message-ID: <CALTJjxGo7SL62CFfRUs=cP5VU_zqOhksX6PTz2E-kybLJK-_0Q@mail.gmail.com>
To: Ryan Sleevi <sleevi@google.com>, Aymeric Vitte <vitteaymeric@gmail.com>
Cc: public-webcrypto-comments@w3.org
On Fri, Dec 14, 2012 at 3:29 AM, Aymeric Vitte <vitteaymeric@gmail.com> wrote:
>
> I am not talking about a partial hash output.
>
> To be clear, the question is how to do what is here
> https://github.com/Ayms/node-Tor/blob/master/src/crypto.cc#l396-416 ( what
> is commented was the initial behavior, ie close the hash after digest, I did
> modify it to keep the state before digest and process it again after digest)
> or here https://gitweb.torproject.org/tor.git/blob/HEAD:/src/common/crypto.c
> (lines 1578-1587, same thing)

What Aymeric Vitte requested is the ability to fork a digest operation
so that we can finish one branch of the fork to obtain the digest of
the data up to that point.

This is used in the CertificateVerify handshake message of the SSL/TLS
protocol, so most native crypto libraries have this function. This
issue was discussed before. Digest is the only operation I know of
that has uses cases for this fork/copy/clone feature.

Wan-Teh
Received on Friday, 14 December 2012 13:59:24 GMT

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