AES faster than RSA Encryption? [closed]

Question

I am trying to test the speed of RSA and AES with openssl in ubuntu.

i used the following code to test it.

echo -n "0123456789012345" > message.txt

openssl genrsa -out private.pem 1024
openssl rsa -in private.pem -out public.pem -pubout


for i in {1..1000}
do
    openssl rsautl -encrypt -inkey public.pem -pubin -in message.txt -out message_enc.txt
done

for i in {1..1000}
do
    openssl rsautl -decrypt -inkey private.pem -in message_enc.txt -out message_dec.txt
done

for i in {1..1000}
do
    openssl enc -e -aes-128-cbc -in message.txt -out aes.bin -K ddf -iv 345

done

Results:

$ time ./rsa_enc 
real    0m3.697s
user    0m1.308s
sys     0m0.680s

$ time ./rsa_dec
real    0m14.273s
user    0m3.172s
sys     0m0.696s

$ time ./aes

real    0m3.790s
user    0m1.408s
sys     0m0.500s

It shows that RSA encrypt is faster then AES encrypt.

Shouldn't AES be faster? Am I doing anything incorrectly?

Thanks.

Answer 1

Besides @jbtule's correct point about the different purposes for RSA and AES encryption, there's something fundamentally flawed in the design of your benchmark.

What you're measuring here isn't just an RSA or AES encryption routine, but the whole execution of these openssl commands.

While it can make sense to use timers outside your external program to measure how one of its functions is performing, doing so requires the time spend doing other things (like parsing the command line parameters, finding the right OpenSSL sub-module, opening the file, reading the file) to be negligible compared with the time required to perform the timed function.

Here, this is clearly not the case, especially with such a short test message.

Answer 2

Why does it matter which one is faster anyway. You really can't use them for the same thing. RSA can only encrypt a very small amount of data.

But generally if you need to encrypt something large with RSA you use it encrypt a random AES key and aes to do your plaintext, but it's more for security reasons based on the block size and decryption speed rather encryption speed.