Adding encryption to Btrfs

Posted Sep 23, 2016 13:41 UTC (Fri) by epa (subscriber, #39769)
In reply to: Adding encryption to Btrfs by koverstreet
Parent article: Adding encryption to Btrfs

I thought that hardware AES was really for the benefit of weaker, embedded processors which can't do software encryption as fast.

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Adding encryption to Btrfs

Posted Sep 23, 2016 16:15 UTC (Fri) by magila (guest, #49627) [Link] (2 responses)

Even on larger CPUs hardware AES is more power efficient. The SIMD units are by far the most power hungry logic units in modern Intel CPUs.

Adding encryption to Btrfs

Posted Sep 27, 2016 14:36 UTC (Tue) by jtaylor (subscriber, #91739) [Link] (1 responses)

I'm curious, do you have a source for that claim?

Adding encryption to Btrfs

Posted Sep 29, 2016 4:31 UTC (Thu) by magila (guest, #49627) [Link]

I'm not aware of any published comparisons. I've done some informal testing on my own machine, a quad core Skylake running at 4.5GHz, with 8K blocks and found:

ChaCha20 achieves 16.4GB/s while consuming 102W or 5.93 microjoules/byte
AES-128-CTR achieves 22.4 GB/s while consuming 87W or 3.70 microjoules/byte
AES-256-CTR achieves 16.6 GB/s while consuming 82W or 4.71 microjoules/byte

You might argue comparing AES-128 to ChaCha20 is unfair, but the fact is those are by far the most widely used variants of each.

ChaCha20 was tested using the benchmark tool from https://github.com/floodyberry/chacha-opt modified to run ChaCha20-avx2 with 8K blocks in a loop
AES was tested using the example code from https://wiki.openssl.org/index.php/EVP_Symmetric_Encrypti... modified to encrypt 8K blocks in a loop.
All tests were done with 4 instances running in parallel.
Power consumption was measured using CPUID HWMonitor.