Today's CPUs are fast enough that performance losses (if any) are only noticeable for local Ethernet speeds, or faster.
Following are some measurements where the different encryption methods were applied between two very old systems, a P5/90 and a 486/100, both running Linux, for copying files with scp across a lightly loaded Ethernet.
The model chosen was 
; a is the startup time in seconds, and b
the sustainable transfer rate in kB/s.
| Encryption | Bandwidth [kB/s] |
| none | 386.1 |
| rc4 | 318.2 |
| tss | 298.5 |
| des | 218.8 |
| idea | 169.6 |
| 3des | 118.2 |
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