Symmetric Keys vs Asymmetric Keys: The Logic

jdredd

Several practice questions have said asymmetric keys are stronger than symmetric keys when the keys are of equal length. The explanation is "a symmetric key length of 128 bits = an asymmetric key length of 2304 bits".

I can memorize this, but if 128 sym = 2304 asym, wouldn't the symmetric key be stronger if both keys were 128 bits long? Wouldn't it take a 2304 bit asymmetric key to give as good encryption as the 128 bit symmetric key making the symmetric key stronger?

Is the answer wrong (not corrected on the publishers site, though)? Maybe I have just gotten confused by the question. I haven't been able to find a good explanation for this question. The logic escapes me if asymmetrical keys of the same length are stronger.

org

Please correct me if I am wrong, but this is my understanding of this.

A 128-bit symmetric encryption algorithm is just as secure as one using an asymmetric encryption algorithm. As I am sure you know, the difference between the two is that symmetric encryption uses the same key for encryption/decryption where asymmetric will use different keys (encrypt with public key/decrypt with different private key).

Now another difference is that encrypting via asymmetric means is more intensive on the system. Therefore it might not be reasonable or as fast to encrypt an entire message via asymmetric means. I might be missing something, as there are many differnet algorithms and methods to encryption, but this has been my understanding.