Dell DX6004S DX Object Storage Application Guide - Page 77
Application Initiated Hash Upgrading
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that the stored content has always been as it is now, and that it has always been associated with the same UUID. Note Range headers are not compatible with integrity seals. If the seal is incorrect, the connection might be closed prematurely. For more information about integrity seals, see Section 20.1, "Integrity Seals". 20.3. Application Initiated Hash Upgrading From time to time, cryptographers and mathematicians may defeat a cryptographic algorithm, making it possible for hackers to generate different content that has exactly the same hash value as some other, previously stored content. This has already happened with the md5 and sha1 algorithms, but not sha256, sha384 or sha512. Unlike other Fixed Content Storage solutions, DX Storage allows a user or application to upgrade a hash algorithm for an existing individual integrity seal. This is done by issuing a READ request with the name or UUID, the current hashtype and hash, and then specifying a different, presumably stronger, hashtype in the newhashtype query parameter. Of course this should be done before any exploit of the old algorithm becomes well known and available. For example: GET http://129.69.251.143/41A140B5271DC8D22FF8D027176A0821?hashtype=md5& hash=7A25E6067904EAC8002498CF1AE33023&newhashtype=sha256 HTTP/1.1 This READ request will first validate the given integrity seal, then reseal it by wrapping the content in the new, upgraded hash algorithm - sha256 in the example. If the requested object fails to validate against its integrity seal, DX Storage will send a 200 OK response but then drop the connection prior to sending the object content. On the other hand, if the object validates properly, a new integrity seal will be returned with the new hashtype and hash value. Copyright © 2010 Caringo, Inc. All rights reserved 72 Version 5.0 December 2010