#1 2020-02-06 11:17:21

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Registered: 2017-04-21
Posts: 1,283

Intel SHA-1 extensions

As many of you already know, (c)XSIBackup in general: Pro and DC makes use of the SHA-1 algorithm to index blocks of data. There are multiple reasons for that: it has excellent dispersion properties, it is available in OpenSSL and it's fast.

SHA-1 was conceived for encryption, not just for uniqueness, like: Murmur or Cityhash, thus we are playing an extra CPU cost for a feature that (c)XSIBackup does not need. That is true, but there is an extra fact that is quite important in the equation.

Most Intel processors that are used in servers nowadays incorporate native ASM extensions for the SHA-1 algorithm and OpenSSL takes advantage of those extensions, making SHA-1 be extremely fast when it comes to hash data.

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