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From "Jonathan D. Knezek (JIRA)" <j...@apache.org>
Subject [jira] Updated: (COUCHDB-625) Pure Erlang alternative to crypto library
Date Wed, 20 Jan 2010 02:25:54 GMT

     [ https://issues.apache.org/jira/browse/COUCHDB-625?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jonathan D. Knezek updated COUCHDB-625:
---------------------------------------

    Attachment: ccrypto.erl

This new version exports the pure functions (prefixed with pure_) for testing, adds test_rand_bytes/1
which reports the number of collisions found in N generated UUIDs, and combines the word expansion
and mixing steps for sha/1.

The SHA1 implementation is about 15% faster than the previous version due to the elimination
of list construction.

Also, after actually checking the sites where sha/1 and sha_mac/2 were called, I'm much less
concerned about speed.  I thought they were being used to calculate the revisions, so I was
worried about possibly handling several MB.  All the uses are dealing with authentication,
though, and this version can hash about 21kB/s on my 1.2 GHz SheevaPlug.

I say give legal a ring. :]

> Pure Erlang alternative to crypto library
> -----------------------------------------
>
>                 Key: COUCHDB-625
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-625
>             Project: CouchDB
>          Issue Type: Improvement
>          Components: Infrastructure
>            Reporter: Jonathan D. Knezek
>            Assignee: Chris Anderson
>            Priority: Minor
>         Attachments: ccrypto.erl, ccrypto.erl
>
>
> On some platforms (in my case a SheevaPlug running on armv5te) it may be difficult or
impossible to obtain a version of Erlang built with support for the crypto standard library.
 I grepped the CouchDB source and have attempted to reproduce the used crypto calls in pure
Erlang.
> I have reproduced the start/0, rand_uniform/2, rand_bytes/1, sha/1, and sha_mac/2 functions,
along with test_sha/1 and test_sha_mac/1 functions to validate the pure Erlang results against
the crypto library's results.  The public non-test functions attempt to first call into crypto
if available, as it is the preferred implementation.
> As I'm not familiar with the build system, app system, etc. of Erlang I am only attaching
the library implementation.  I'm sure more work would be required to fully integrate it into
CouchDB if accepted.
> As far as licensing goes, SHA1 is defined in NIST FIPS 180-2 (http://csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf),
and according to the IETF, the patent covering the algorithm has been made royalty-free (https://datatracker.ietf.org/ipr/858).

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