client: optimize encryption

[ernado]

Currently encryption of every message requires allocation, because each message has different encryption key.

We can't reuse AES buffer due to crypto/cipher design.

Related issue in go:
golang/go#39365

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[tdakkota]

I think we're fast enough.

grammers.rs:

test encrypt_b0016  ... bench:         157 ns/iter (+/- 3) = 101 MB/s
test encrypt_b0256  ... bench:         496 ns/iter (+/- 20) = 516 MB/s
test encrypt_b0512  ... bench:         856 ns/iter (+/- 62) = 598 MB/s
test encrypt_b1024  ... bench:       1,636 ns/iter (+/- 6) = 625 MB/s
test encrypt_kb0016 ... bench:      23,062 ns/iter (+/- 425) = 710 MB/s
test encrypt_kb0128 ... bench:     182,503 ns/iter (+/- 5,618) = 718 MB/s
test encrypt_kb0512 ... bench:     748,600 ns/iter (+/- 18,533) = 700 MB/s

gotd:

cpu: Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz
BenchmarkIGEEncrypt
BenchmarkIGEEncrypt/16b
BenchmarkIGEEncrypt/16b-12           13522802          79.92 ns/op   200.20 MB/s         0 B/op         0 allocs/op
BenchmarkIGEEncrypt/256b
BenchmarkIGEEncrypt/256b-12           3048024         381.1 ns/op   671.66 MB/s         0 B/op         0 allocs/op
BenchmarkIGEEncrypt/512b
BenchmarkIGEEncrypt/512b-12           1725553         691.3 ns/op   740.61 MB/s         0 B/op         0 allocs/op
BenchmarkIGEEncrypt/1024b
BenchmarkIGEEncrypt/1024b-12          1000000        1344 ns/op   761.94 MB/s         0 B/op         0 allocs/op
BenchmarkIGEEncrypt/16384b
BenchmarkIGEEncrypt/16384b-12           57978       20085 ns/op   815.71 MB/s         0 B/op         0 allocs/op
BenchmarkIGEEncrypt/131072b
BenchmarkIGEEncrypt/131072b-12           7404      162335 ns/op   807.42 MB/s         0 B/op         0 allocs/op
BenchmarkIGEEncrypt/524288b
BenchmarkIGEEncrypt/524288b-12           1696      648719 ns/op   808.19 MB/s         0 B/op         0 allocs/op
PASS