You don't normally use public key encryption in satellites, it is some sort of block crypto. CCSDS (a bunch of standards for space applications that is quite po

You don't normally use public key encryption in satellites, it is some sort of block crypto. CCSDS (a bunch of standards for space applications that is quite popular in the industry) recommends AES-HMAC for authentication and AES-GCM for both authentication and encryption. My experience with a LEON processor ~100 MHz is that it is hard to get much throughput out of an AES implementation.