OpenStack Object Storage (swift)

Need strong SHA1 ETag support

Asked by Sunding Wei

Hi Sir

By reading the Swift API documents, the ETag was MD5 checksum, I am designing a global deduplication system, all chunks are already checked by strong SHA1 algorithm, how can I specify the ETag checksum algorithm to SHA1?

I don't want to MD5 a chunk which already checked by strong SHA1.

Thanks.

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Chuck Thier
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Best Chuck Thier (cthier) said : 		#1

To support this nativly in swift, the hashing code in swift would have to be refactored a bit. If you just need to store the sha-1 hash with the objects, you can store it in the object metadata.

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Sunding Wei (weisunding) said : 		#2

Changing the swift code will solve my question.

Would it's possible that Swift can be configured to use SHA1 for ckecksum officially? MD5 collisions already found.

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John Dickinson (notmyname) said : 		#3

There are no plans to change the hashing algorithm in Swift. Swift does not use md5 for cryptographic security. In the case you are looking at, the problem to solve is only to ensure that the bits on disk and the bits transferred on the network are correct. In that case, md5 is quite sufficient and has the added benefits of being both widely available and fast enough.